Tuesday, June 25, 2024

Iris Publishers- Open access Journal of Engineering Sciences | The Root of Silica Scale Formation and Its Remedy

 


Authored by Mai Al Saadi*,

Background

Naturally, silica present in water feed in the range of 1-100 ppm. It is existed as silicic acid (H2SiO3) which is a weak acid and dissociated at or below neutral pH [1,2]. The presence of silicic acid lead to form silica colloidal in water at neutral pH. But when pH exceeds the neutral, silicic can be dissociated and form silicate anion (SiO3 2-), which can react with positive ions like calcium, magnesium, iron, manganese and aluminum to form insoluble silicates [3]. It is essential to control the iron content to be minimum as much as possible, at least about 0.05 ppm, in order to avoid corrosion and scale formation. The silica scale formation usually takes place at pH level below 8.5, whereas Magnesium silicate scale form at pH 8.5 and above, because as pH increases the possibility of positive silicates salt to form increases. Silica scale is complex and amorphous product from colloid silica and a complicated mixture of numerous components often including metals ions [3].

Factors of Polymerization Process

Commonly, the concentration of dissolved silica in aquifer waters (200-350 ⁰C) of the geothermal system is strongly high, and it is about 300-700 mg/kg SiO2 (Fournier and Rowe, 1966; Mahon, 1966). Once water contacts the surface, the temperature decreases down to 100 to 200 ⁰C, and the saturation for amorphous silica can occur (Gunnarsson and Arnorsson, 2003). The precipitation of amorphous silica can occur at low temperature below its saturation, otherwise the polymerization will start during saturation point. Uncontrolled precipitation or polymerization can occur over various locations at surface conditions. It is found that silicic acid precipitates on any surface which contain OH groups (Iler, 1979). Hydroxide minerals can grant their OH groups to co-precipitate with amorphous silica. Polymeric silica has lower tendency to precipitate than monomeric silica, because it forms colloids which can remain suspended in the solution. The conditions for polymerization in terms of oversaturation, temperature and pH will be explained. The oversaturation solution can cause polymerization for unionized monomeric silica by reducing the concentration of monomeric silica, for example from 777 mg/kg to 400 mg/kg within first minutes of reaction. Oversaturation of amorphous silica solution is difficult to be treated, and it will lead to polymerization, which increases the risk of silica scaling. Usually, more polymerization can be at low temperature because the concentration of silica will be higher at cooler temperature so that will lead to reduce the concentration of monomeric silica at those temperature. Even though the nature of water is basic and the pH between 8 to 10, the polymerization of monomeric silica has capacity to increase the pH by 0.2 or 0.4, due to removing silicic acid from solution. This can affect the degree of saturation for minerals that have pH-dependent solubility, such as hydroxides, calcite and magnesium silicates [4]. At neutral pH, the precipitation is at the highest amount, while the silica solubility is the lowest (Iler, 1979), in addition, the concentration of monomeric silicic acid polymers is less at pH 11 to 12 dues to strong alkalinity.

Factors of Silica Scale Formation

Silica scale formation usually takes place at pH levels below 8.5, Silica in water can be as reactive silica, colloidal silica and particulate silica. Silicate compounds exist in the form of amorphous, which is soluble in alkali solutions and crystalline form is nonstable. When pH exceed neutral silicic acid can be dissociated and form silicate anions (SiO32-). which can react positive ions like Ca, Mg, Fe, Mn and Al to form insoluble or slight soluble silicate Metal ions such as magnesium and calcium in the water must be taken into account, because at alkaline conditions silica combines with magnesium or calcium ions and forms calcium or magnesium silicate deposits [5]. Magnesium silicate scale forms at a pH above 8.5 in water has high Mg2+ ions. Silicates prefer to react with Magnesium when both Calcium and Magnesium are present. Mg2O4 Si compounds are softer and easier to remove from the equipment surface compared to calcium silicate compounds. Also, it does not adhere to metal surface, nor destroy stainless steel, while the opposite is true with calcium. In addition, Mg concentration can eliminate or minimize calcium scaling in process equipment. At high pH, there is a chance for Mg to react with silicates ions to form silicate compounds. it had found that both Al and Fe ions have high potential to react with silicate so it is crucial to know the source of them and ensure their concentration is less than 0.05 mg/l in feed water. Regarding, aluminum silicates can be soluble at high pH of approximately 7. Therefore, increasing pH will reduce the risk of AL silicate deposition. Low temperature reduces the solubility of amorphous silica (it is any form of silica with lacking in crystal structure such as (Silica gel, Gelatinous gel, Silica sol or Colloidal silica, Opal and Silica glass. However, the solubility of other silicates increases as the temperature increases.

Methods to prevent the occurrence of silica scaling at surface facilities

1. Injection of scaling inhibitor liquid (usually H2SO4) to reduce the pH unit, or caustic soda to rise the pH unit into the brine pipeline in order to stop the formation of scaling for hours (brown, 2011)

2. Separator pressure adjustment can also be applied (sometime unacceptable for economic power generation)

3. Development of double-flash separation leads to higher pH and lower silica scaling.

4. Scale can be avoided by application of three water treatment techniques inhibition of scale deposits, corrosion and prevention of microbiological fouling.

5. Removing silica from the makeup water through “hotlime softening” by precipitation with Mg(OH)2 or MgCl2 followed by filtration, by inhibition (elimination of colloidal silica formation) and by dispersion (stops silica polymerization at early stages by preventing the growth of large particles and their attachment to surfaces) .Example for inhibitors (yellow metal: copper and admiralty brass, polyacrilaies, Boric acid ,dendrimers and quarts), corrosion inhibitors, dispersant polymers and tracers and inhibitors for silica or magnesium silicate are less common. According to one study low dosage of inhibitor can have great influence on Si removal at pH 10.5 and can eliminate 90% of the silicon.

6. Addition of EDTA can inhibit magnesium from catalyzing the polymerization of silicic acid, EDTA is effective and dose dependent when it is high, then it will have a little effect on silica solubility, while low dose provides more effective solubility of silica.

7. The potential of deposition will decrease in the condition of the presence of saline solution, the repulsive forces will reduce which can cause aggregation of silica

Executive method for treating silica scale

Colloidal silica is not affected by the ion exchange process, and when it forms a complex with organic matter it can foul the resins [6]. Colloidal silica is converted into reactive silica at high temperature and pressure, which leads to volatilize them along with steam and get deposited as glassy scale. Some industries have additional investment in order to reduce the number of shutdowns by implementing new technology such as ultra-filtration. There are other means to remove colloidal silica (non- reactive silica). Coagulation which can remove approximately 80 to 90% of colloid silica isn’t easy to implement, because colloids are attached with organic matter which require for pre-chlorination in order to oxidize the organic matter and maintaining optimal pH condition through dosing of a primary coagulant like alum and flocculation as polyelectrolyte [6].

Many industries have addition investment to reduce the risk of silica scale by utilizing ultrafiltration, because it removes the maximum amount of nonreactive silica, firstly by removing the bulk in the pretreatment plant or demineralization process then push it to ultra-filtration (UF) system. It is required be installed at the outlet of the mixed bed (MB unit) and the membranes of UF with molecular weight cut off (MWCO)of 100,000 remove up to 99% while the tighter membrane with an MWCO of 10,000 remove up to 99.8 % [6,7]. For the existing plants which face problems of silica scale, it is good to add hollow fiber UF membranes downstream of the MB unit to capture the colloidal silica that will escape the pretreatment and ion exchange beds (Figure 1).

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Iris Publishers-Open access Journal of Orthopedics Research | Use of a New Arthrometer to Assess Knee Pathology

 


Authored by Dawn T Gulick*,

Abstract

Purpose: The purpose of this study was to compare the results of Mobil-Aider testing on the involved and uninvolved knees of individuals with anterior cruciate ligament (ACL) injuries to MRI results.
Methods: Individuals with reported knee injuries (N=26) were tested for ACL laxity using the Mobil-Aider arthrometer. A foam bolster was used to position the knee in 20-30° flexion. The arthrometer was used to perform a Lachman test on the tibio-femoral joint. The maximal translation of 3 measurements on each knee was recorded. The clinical data and the MRI results were matched.
Result: For the test of between-subject differences, an interaction effect was found between side and MRI result (p = 0.008). A simple main effect was found in between involved versus uninvolved side (p = 0.001). There was no simple main effect size found for MRI result (p = 0.415).
Conclusion: Excessive anterior translation of the knee is part of the patient presentation of an ACL injury. The clinician should also be cognizant of the mechanism of injury, the report of a “pop,” presence of rapid swelling, loss of range of motion, and instability. This is the first study using the Mobil-Aider to assess ACL injuries. Although the device has been validated and determined to be reliable in prior studies of healthy individuals, testing individuals with injuries are important to demonstrate its clinical value. The sample size is limited but the study was adequately powered to be able to state the Mobil-Aider has the potential to provide valuable clinical information when assessing ACL injuries.

Keywords: Knee sprain; ACL injury; Lachman technique; Arthrometer

Introduction

There are over 7.2 million orthopedic injuries annually in the USA. Approximately 6.6 million knee injuries presented to United States emergency departments between 1999 and 2008 [1]. It has been estimated 40% of all sports related injuries are of the knee. Of those knee injuries, anterior cruciate ligament (ACL) damage is the most common (over 200,000 per year). Furthermore, it has been estimated that approximately 74% of acute ACL injuries are missed in the emergency department [2].

Part of the challenge in assessing ACL damage is the technique used. The Lachman test is considered the gold standard with sensitivity of 63-99%, specificity of 42-100%, (+) likelihood ratio of 1.12-40.81, and (-) likelihood ratio of 0.02-0.83 [3-14]. The wide range of the statistical data can be related to the criteria for a positive test. Are the positive criteria a lack of an end feel or excessive anterior translation relative to the contralateral side? As a dichotomous test, what constitutes “excessive translation?” It is generally believed that when excessive translation is considered, 5 millimeters or more of increased anterior knee translation on the KT-1000 test is indicative of an ACL either torn or stretched to the point where it is no longer functional [15]. Likewise, Bach et al (1990) reported a side-to-side KT-1000 difference of 0.2 mm is considered normal and differences of 4.8 and 5.5 mm are present in acute and chronic ACL injuries, respectively [16].

Until recently, the KT1000 was the only clinical device used to quantify ACL injuries. However, there are a number of interfaces in the use of the KT1000. The device straps on the knee in a very precise way but the function of the device actually pulls it away from the anterior tibia. If the straps are not secured tightly, a gap occurs between the device and the tibia. This can produce an erroneous value. The counter force to stabilize the proximal leg is delivered via the patella. It is not only uncomfortable, but also not consistent with the Lachman technique of stabilizing the femur. In fact, several studies have reported substantial variability in the measures using the KT1000/2000 [17-19]. Wiertsema et al [20] examined the reliability of the KT1000 arthrometer and found the intra-rater reliability and the inter-rater reliability to be low (ICC = 0.47 and 0.14). Barcellona et al [17] stated that the KT1000 and KT2000 knee joint arthrometers (MEDmetric Corp, San Diego, CA) have been shown to over-estimate the measurement of knee joint sagittal laxity between 22% and 24%.

In 2021, the development of the Mobil-AiderTM (Figure 1) (Therapeutic Articulations, LLC, Spring City, PA) sought to address the pain points of quantifying ACL laxity via simple positioning, stabilizing the femur with contoured attachments, and the use of a light-weight tool that pulls the tibia into the device in the same format as the Lachman test (Figure 2). The Mobil-Aider TM has been shown to be valid in the lab (2% margin of error) when compared to the Zeus Smartzoom [21]. Clinical testing of the posterior translation of the shoulder and volar translation of the wrist have demonstrated reliability of 0.77-0.83 and 0.90, respectively [22- 23].

Magnetic resonance imaging (MRI) is often used for ACL injury diagnosis [14,24]. However, the ability of MRI to identify partial ACL tears has been called into question [25]. Furthermore, MRI is a static image and offers no data about the dynamic instability of the knee (Figure 1&2).

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The purpose of this study was to assess the ability of the Mobil- AiderTM device to identify injury to the ACL. The goals were 1) to see if the Mobil-AiderTM consistently identified laxity associated with ACL injuries; 2) identify the magnitude of the anterior displacement present in injured, partial, and complete tears as compared to intact contralateral ACL; and 3) compare the magnitude of displacement with that of the MRI.

Methods

Participants

Eligible participants were anyone over 18 years of age who was suspected to have an anterior cruciate ligament injury or had an MRI with confirmed ACL damage. Participants needed to have an uninjured contralateral knee for comparison. Individuals who had a prior surgery were not eligible. All participants had a scheduled appointment with the researcher (SH) for a suspected knee injury. At the conclusion of the knee examination, the study was explained to the patient, and s/he was asked if s/he was willing to give permission to test his/her knees. Researcher #3 (DG) obtained consent and performed the testing. The uninvolved knee was tested first, then the involved knee. Researcher #3 was blinded to the MRI results prior to testing.

Procedure

The testing procedure involved placing a foam bolster under the knee to obtain a standardized amount of flexion (approximately 20- 30 degrees) in the supine position (figure 2). The tibio-femoral joint line was identified. The device axis was aligned with the joint line and secured on the knee with Velcro straps around the thigh and the calf. The device was set in the “A” mode to hold the maximal reading of anterior translation of the tibia on the femur (Lachman test). The maximal translation of 3 measurements was recorded on the data form for each knee. The MRI results were obtained. The MRI was interpreted by a musculoskeletal radiologist and confirmed by a fellowship trained orthopaedic surgeon (SH). Both the radiologist and surgeon were blinded to the Mobil-AiderTM measurements. The clinical data and the MRI results were matched.

Statistical analysis

The MRI data was coded as “0” for intact ACL, “1” for partial damage to the ACL, and “2” for complete tear of the ACL. A two-way ANOVA was used to compare the ACL laxity of the involved versus uninvolved knee with the MRI result after determining that the data were normally distributed, and Levene’s equality of error variance test had no significant differences. Data were analyzed using SPSS version 27 (IBM SPSS Statistics for Windows, Version 27.0. Armonk, NY: IBM Corp). Descriptive statistics including frequencies, means and standard deviations were calculated in order to describe the sample.

Result

The participants in the study included 12 females and 14 males with a mean age of 32.3 (SD=13.0). Nine had left knee involvement and 17 had right knee involvement. Six were found to have no ACL tear, 10 had a partial and 10 had a full ACL tear. The means and standard deviations of the involved/uninvolved knees for each condition are displayed in Table 1. The mean difference between the involved and uninvolved knees were -0.18, 2.05, and 3.38 for the no tear, partial tear, and complete tear, respectively (Table1).

Conclusion

The present review shows that minimally invasive percutaneous US-guided surgery for CTR offers multiple technical possibilities. As only four of these techniques have been the focus of RTCs, more work is needed to assess the efficacy of this approach in improving the pain and hand functionality problems experienced by patients with CTS.

Table 1: Mean, Standard Deviation of Involved/Uninvolved Knees with MRI Results.

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For the test of between-subject differences, an interaction effect was found between side and MRI result (p = 0.008). A simple main effect was found in between involved versus uninvolved side (p = 0.001). There was no simple main effect size found for MRI result (p = 0.415).

Discussion

The Lachman test is a passive accessory movement performed on the knee to assess the integrity of the ACL. Despite being widely accepted in the orthopaedic community, there are several issues related to the performance of the Lachman test. First, a mismatch in the size of the patient’s leg to that of the clinician’s hands can make it difficult to stabilize the knee and obtain maximal anterior tibial translation. Second, positioning of the knee in 20-30 degrees of flexion and relaxation of the hamstring are important to not block the translation of the knee. Finally, the inability to quantify millimeters of translation can be a significant concern when comparing the involved to uninvolved knee.

There are two alternatives to the Lachman to address the larger diameter leg of the patient and/or smaller hands of the clinician. Adler et al [26] described a modification of this method, which they called the “drop leg Lachman test.” In supine, the patient’s leg is abducted off the side of the examining table, and the knee is flexed to 25°. The clinician’s hand stabilizes the femur against the table while the patient’s foot is held between the clinician’s knees. Thus, the examiner’s other hand is free to apply the anterior translation force to the tibia. Another alternative is the “prone Lachman test.” In this position, with the knee in 25 degrees of flexion, the thigh does not need to be stabilized and gravity helps to translate the tibia anteriorly (Figure 3).

The drop leg and prone Lachman both address the issue of a “size” mismatch and even the knee positioning but neither provide any quantification of the amount of tibial translation. When one is applying a significant amount of force to stabilize the thigh and translate the tibia, distinguishing a few millimeters difference between the knees can be very challenging. Endfeel is often used to assess the ACL qualitatively. The lack of an endfeel may be indicative of a complete tear but when a partial tear is present a subjective endfeel will not contribute information about the magnitude of the injury. Thus, having objective values can contribute to the assessment of the ACL is important. Having a valid and reliable device is also important. The statistically significant differences of the magnitude of the linear translation in the knee injuries in this study corresponded to the MRI results (Figure 4). Larger differences between knees (3.38 mm) corresponded with complete tears, while smaller differences (2.05 mm) corresponded with partial tears. Participants with no ACL injury had no difference between the knees (-0.18 mm). Being able to quantify the magnitude of an ACL injury with a dynamic testing technique can assist the clinician in determining a treatment course of action. Although the sample size of this study was limited (N=26), it was found to be adequately powered (81.8%) for the interaction effect of side and MRI result. As an introductory study for using the Mobil-Aider TM on joint pathology, the current study demonstrates the device has promise for accurately quantifying ACL laxity (Figure 4).

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Clinical Significance

Excessive anterior translation of the knee is part of the patient presentation of an ACL injury. The clinician should also be cognizant of the mechanism of injury, the report of a “pop,” presence of rapid swelling, loss of range of motion, and instability. This is the first study using the Mobil-AiderTM to assess ACL injuries. Although the device has been validated and determined to be reliable in prior studies of healthy individuals [21-23,27-29], testing individuals with injuries are important to demonstrate its clinical value. The sample size is limited but the study was adequately powered to be able to state the Mobil-AiderTM has the potential to provide valuable clinical information when assessing ACL injuries.

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Monday, June 24, 2024

Iris Publishers-Open access Journal of Civil & Structural Engineering | 2021 Sea level rise projections by the Intergovernmental Panel on Climate Change for Coastal Design

 


Authored by James R Houston*,

Introduction

The Intergovernmental Panel on Climate Change (IPCC) delayed its normal six-year publication cycle of climate assessments after its Fifth Assessment Report (AR5) was published in 2013 [1] because there was an explosion of research on climate change that needed to be evaluated. IPCC’s full Sixth Assessment Report (AR6) will be published in 2022. However, in August 2021, IPCC published the portion of AR6 [2] that deals with the physical basis for climate change including sea level rise. IPCC [2] was supported by updated projections of the contributions of Antarctica [3] and Greenland (The Ice Sheet Mass Balance Inter-Exercise 2020) to sea level rise. IPCC [2] has been per reviewed extensively with the first draft receiving comments from 750 reviewers and the second draft from 1279 peer reviewers [4]. IPCC [1] used temperatures that were projected for 2100 based on Representative Concentration Pathways (RCPs) that describe different climate-scenario futures. Scenario labelling is based on possible radiative forcing values by 2100. For example, RCP1.9 and RCP8.5 are scenarios with radiative forcing values in 2100 of 1.9 and 8.5 watts/m2 respectively. Shared Socio-economic Pathways (SSPs) are the climate-scenario futures used in IPCC (2021a), but except for some minor differences relating to climate, SSPs are the same as RCPs. They were the same for sea level rise projections. Table 1 shows IPCC [2] projections to 2100 relative to sea level in 1995-2014. Projections are mean rises with parenthetical numbers representing standard deviations from the means (Table 1).

Table 1: Sea level rise projections for 2100 published in IPCC [2]. Projections are in meters.

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After eight years of study of climate change and sea level rise with a focus on sea level rise contributions from Antarctica and Greenland, the best science led to 2021 IPCC projections that are larger than IPCC [1] projections to 2100 by only 0.1-0.3 m. IPCC [2] introduced new two projections not in IPCC [1] that raise the possibility of sea level rises greater than those in Table 1. However, IPCC [2] notes that it has “low confidence” in both projections. One arises from a scenario called Marine Ice Cliff Instability (MICI) in which West Antarctic ice shelves disintegrate. IPCC [3] noted that only a single ice sheet model represents MICI [5] and “the validity of MICI remains unproven” [2]. Moreover, a recent paper in Science [6] presents evidence that reduces further the chances of MICI. However, if MICI were to occur, IPCC [2] says it could raise sea level to 2100 by 0.99 m (0.82-1.19). The second low-confidence projection is based on a single Structured Expert Judgement (SEJ) survey [7]. Thirteen experts met in Washington DC and nine in London in 2018 and provided anonymous judgements on future sea level. Sea level contributions from Antarctica were key in their estimates of large rises by 2100. However, not one of the 22 were among the 67 Antarctic experts who projected sea level rise contributions from Antarctica in IPCC [3]. IPCC [2] notes it has low confidence in SEJ projections because “individual experts participating in the SEJ study may have incorporated processes in whose quantification there is low confidence and the experts’ reasoning has not been examined in detail.” IPCC [2] gives SEJ projections of 1.00 (0.70- 1.60) m. Some decisions relating to coastal projects have time horizons shorter than 2100. For example, beach nourishment can be started, stopped, increased, or decreased quickly. IPCC [2] has projections to 2050 with mean values shown in Table 2. The projections are again relative to 1995-2014, which is centered in 2005. From 2005-2020 sea level rose 3.3 mm/yr, so to make the projections relative to about 2020, 0.04 m was subtracted from IPCC [2] results (Table 2).

Table 2: IPCC [2] projections from 2020-2050.

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Table 2 shows that mean rises from 2020 to 2050 vary from 0.14 to 0.19 m (5.5 to 7.5 in). That is, the difference in projections between the most benign (SSP 1.9) and worst-case (SSP 8.5) scenario is only 0.05 m (2 in). Even the “low confidence” projections have mean values only 0.01 m higher than the SSP8.5 value from 2020-2050. Rises do not depend greatly on scenarios until after at least 2050. Houston [8] noted that some U.S. agencies have sea level rise projections that differ among themselves and with the IPCC [1], leading to confusion, a lack of credibility, and an undercutting of the IPCC. The U.S. government was the driving force that formed the IPCC to produce climate reports backed by the world’s leading climate scientists [9]. U.S. agencies should rally around using IPCC [2] climate change projections, including sea level rise projections [10].

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Iris Publishers-Open access Journal of Biology & Life Sciences | Larger to Smaller Evolution Evidence on Land, Large Blue Whales in Oceans and the 20th Order of Mammals discovered

 


Authored by James T Struck*,

Introduction

There is some evidence that body sizes of animals have decreased as Giganotosaurus, Diplodocus at 85 feet, Argentinosaurus at up to 130 feet or Sauropods are large while humans are smaller even though blue whales are still large as well at about 95 feet. Evidence of body size decline on land can be argued for.

I discovered the 20th order of mammals consisting of the Aye, Panda, lemurs and marmosets with 6 fingers. A new order of mammals shows more evidence of diversity of life on Earth. Humans have 6 fingers sometimes too.

Discussion

I made a trip to the Field Museum of Natural History for an Illinois Free Day and made 4 discoveries. “Some individuals are better adapted for survival in a given environment than others. This is called the “Survival of the fittest’ [1].

An extension of survival of the fittest arguments is that on land we see survival of the smaller land organisms in many cases associated to the disappearance of diplodocus, giganotosaurus, brontosaurus, and Argentinosaurus.
1. Body size of animals has decreased from 67 million years ago to today. Maximo and Tyrannosaurus Rex were larger than current humans. Many dinosaurs including sloths were larger than humans today.
2. Tale size in older animals is larger from glyptodont to Maximo to Tyrannosaurs Rex. The reason for tale retraction is unclear.
3. Some of the growth in body size can be linked to flowering plants.
4. Field Museum argues Maximo is the largest animal, but that is unproven as larger animals may still show up. Blue whales in oceans measure about 95 feet.
5. I discovered the Octa Leg and Octa arm group consisting of the crustacean lobster and crab and mollusks Octopus and Squid. I discovered the Sixteen Leg group of shrimps and 10 Leg Prawn. I made advances in recognizing multiple leg creature groups. Even though there is a decrease in total size there are still a large number of legs.
6. Fingered Animals- A 20th order of Mammals is diverse existing in Asia, South America, and Africa. All the examples from this order of mammals exist in the primate group.

Conclusion

We have evidence of a new order of mammals and a decrease in total body size on land, maintenance of large body size in oceans as many sauropods like brontosaurus are larger than humans and pandas, seals, tigers, lions, rhinos, squirrels and giraffes and hippos and raccoons.

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Friday, June 21, 2024

Iris Publishers-Open access Journal of Complementary & Alternative Medicine | Medicinal Uses of Juniper Tree Cones

 


Authored by Loutfy I El-Juhany*,

Opinion

The juniper plant is classified within the Plantae kingdom as it follows the Coniferophyte division, Pinopsida Class, Pinales order, Cupressaceae family, and Juniperus genus [1]. The genus Juniperus includes 60 species, all of which are found in the northern hemisphere, with only J. Procera in the southern hemisphere [2]. A number of juniper species are cultivated as ornamentals and are useful for their timber. Moreover, many parts of the juniper tree are used in the treatment of many diseases that afflict humans, and some of them have been known since ancient times. The cone of the juniper is the part that is referred to as the berry; it may be called fruits figuratively. The importance of juniper tree as a medicinal plant is due to the chemical composition of its cones. Research has shown that juniper berries contain at least 87 chemical compounds and are extremely high in flavonoid and polyphenols which are antioxidants [3]. The oldest record of the medicinal use of juniper fruits goes back to an ancient Egyptian papyrus dating back to 1500 BC, which contains a prescription for treating a tapeworm infection using juniper fruits [4]. The ancient Egyptians used juniper to mummify the dead bodies [5]. The Romans also used the fruits of juniper to purify the stomach from diseases, while the famous herbalist Culpeper from the Middle Ages recommended treating a wide range of ailments using juniper, including the treatment of flatulence (which Juniper oil is still used today). Juniper fruits have been used as medicine by many civilizations, and in ancient Egypt physicians used volatile juniper seed oil as a laxative since about 1550 BC [6]. Juniper cones have been found in ancient Egyptian tombs in multiple locations. The fruits of Juniperus excelsa and Juniperus oxycedrus were found in the tomb of Tutankhamen (1341-1323 BC) [7]. The Greeks used juniper fruits as medicine long before their use in foods was mentioned [8]. They also used juniper fruits on many of their Olympic Games occasions due to their belief that juniper fruits increased the physical endurance of athletes [9]. In the Americas, Zuni Indians used juniper fruits to aid in the birth process, while other Indians used juniper fruits and leaves to treat infections, arthritis, and wounds [10]. Western tribes in America used a mixture of the fruit of the common Juniperus communist with the bark of the roots of Berberis vulgaris to treat diabetes. Clinical studies have proven the effectiveness of this mixture in treating insulin-dependent diabetes. It has been shown that compounds in these two plants, when combined and swallowed, stimulate insulin production in fat cells in the body, as well as stabilize blood sugar levels. Indians also used juniper fruits as a contraceptive [11]. Juniper is used as a diuretic, antiseptic, and antimicrobial, as it has anti-inflammatory, anti-rheumatic, and stomachache properties, which are attributed to the volatile oils found in the cones [6]. This oil is a mixture of terpenes, flavonoids glycosides, sugar, tar, and resin, with terpenes-4 and terpinen-4-ol, a diuretic compound that stimulates the kidneys and the flavonoid am into flavones have antiviral properties. It is believed that resins and tar can be used in the treatment of skin diseases such as psoriasis, and there is deoxypodophyllotoxins that can help inhibit the herpes simplex virus [6]. Among modern uses of juniper are also treatment of urinary tract infections and bladder because it is a powerful diuretic, and is also used to relieve chronic arthritis, gout, fluid retention, kidney disease, menstrual disorders, heartburn, indigestion, rheumatism, and other diseases [6]. The chemicals present in juniper fruits stimulate the contraction of the uterine muscles and thus can be helpful in facilitating the labor process. The same properties of these substances have also been used to abort an unwanted pregnancy [4]. Juniper was used by British herbalists to promote menstruation in women, and by the beginning of the 19th century American herbalists were using it as a treatment for congestive heart failure, urinary tract infections, and gonorrhea [6]. Juniper fruits have been used as a traditional treatment for cancer, arthritis, rheumatism, bronchitis, tuberculosis, and gout. Doctors often chew juniper cones when treating patients so that they would not be infected [6]. In the seventeenth century, the herbalist Nicholas Culpeper recommended the use of mature juniper cones to treat conditions such as asthma, and sciatica, as well as to accelerate labor [11]. Juniper cone oil is known to be an antiseptic, analgesic, and sedative, and it has also been known to be useful in treating tuberculosis, jaundice, eczema, and others [12-17]. In general, various materials are extracted from juniper trees that are useful in treating many diseases and health problems that afflict humans, and they are used in the habitats in which these trees are spread, and among those diseases are diarrhea, abdominal pain, tumors and respiratory tract injuries such as coughing and indigestion, as well as bark ash is used in treating some skin diseases. It is also used to relieve head and tooth pain, coughing, and to treat some skin diseases such as eczema, and it prevents hair loss [18]. Some juniper tree products are used as odor repellant incense in hospital patient rooms and clinics.

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Iris Publishers-Open access Journal of Textile Science & Fashion Technology | Perspectives of Textile Waste Management in the U.S. – A Review

 


Authored by Sumit Mandal*,

Abstract

In the last 30 years, global consumption of textile articles has increased significantly. Population increase along with the booming of fast fashion trends are facilitating the growth of global textile consumption. The current pandemic situation is raising the consumption of protective clothing. Such scenarios are diminishing the lifecycle of textile products significantly. Consequently, the world has observed a considerable increase in textile waste generation in recent years and is predicted to increase even more in the coming years due to the current consumption trends. Despite being highly recyclable, much of such wastes go into open dumps or landfills. The U.S. has also seen an increase in textile waste generation, and most of the wastes is landfilled. Disposing of such a huge waste stream can be identified as mismanagement due to its impact on the environment, society, and corresponding footprints. To counter the impact of the rising textile wastages, it is necessary to address sustainable approaches via a structured textile waste management system. This review aims to observe the textile waste scenarios based on the U.S.’s perspectives. An overall aspect of textile waste generation has been presented briefly while considering the current circumstances in the U.S. Current trends of textile waste management in the U.S. have been discussed while mentioning other available options in waste management. Lastly, this review has proposed some probable study directions that would facilitate establishing efficient textile waste management across the U.S.

Keywords:Fast fashion; Municipal solid waste; Textile waste; Wastewater; Waste management; Recycle; Reuse; Production wastages; Preconsumer textile wastages; Post-consumer textile wastages

Abbreviation:EPA- Environmental Protection Agency; ISO - International Organization for Standardization; COD- Chemical oxygen demand; CFRCode of Federal Regulations; NPDES- National Pollutant Discharge Elimination System; POTW- Publicly Owned Yreatment Works; PFAS- Per- and Polyfluoroalkyl Substances; PPE- Personal Protective Equipment

Introduction

Global consumption of textile products has been doubled in the last two decades due to the increased population and introduction of fast fashion [1-3]. In North America, the average trend of textile consumption in a year is 37 kg per person which is more significant than in Australia (27 Kg) and western Europe (22 Kg) [1,3]. With increased textile consumption, production, pre-consumer, and post-consumer textile waste is also growing. Each year Americans generate around 16 million tons of textile waste, which makes up around 6% of overall municipal waste [2]. The introduction of the circular textile economy (fabrication-utilization-recycling/reuse) is encouraging the recycling of such textile waste. Recent statistics show that 700,000 tons of the waste are exported overseas, whereas 2.5 million are recycled [2]. However, the prevailing traditional linear model of the textile economy (fabricationutilization- disposal) still contributes to more than 3 million tons of incinerated apparel and 10 million tons of textile landfills [2,4]. Such a discrepancy in the disposed and recycled textile waste quantity is a genuine concern to be addressed to achieve a sustainable future. Due to the rising concern towards a sustainable future, the recycling of textile products has increased steadily over the last six decades [5]. However, the percentage of recycled clothing is less than 1%, whereas the amount sent to landfills has quintupled over the years [5]. The data summarizes that most unwanted clothing in the U.S. is still preferred to be left in the environment rather than recycled or reused.

The current trend in the predominant linear model of the textile economy is generating more waste due to the introduction of fast fashion, lack of government regulations, uninformed consumers, and throwaway culture. The lifecycle of the textile product is much less than at any other time in the previous era. Overconsumption of textile products is becoming more prominent due to the fast-fashion trends [6]. Fast fashion, the quick response to the everchanging consumer fashion demands by the fashion retailing house, generates new fashion trends within a very short period. As a result, the current fashion trends are becoming obsolete within a very short time. The previous long fashion cycles are becoming short cycles of transient fashion trends. Each trend creates its own sets of wastage throughout the fashion cycle: production wastes, pre-consumer wastes, and post-consumer wastes. Production wastes from the apparel manufacturing steps, unsold or damaged products at the pre-consumer stage, and worn-out, out-of-fashion products at the post-consumer stage are the sources of such textile wastes. The textile wastes are increasing in quantity with the throwaway tendency of the fast-fashion consumers. Increased population and lack of government regulations of waste apparel disposal are contributing to increasing the wastes even more. Steps to control the increasing textile wastages are essential to adopt early to have a smaller environmental footprint generated through the fashion industry. Reuse or recyclability provides a better sustainable approach to managing the increasing textile wastes.

According to the data provided by the U.S. Environmental Protection Agency (EPA), textile wastes contributed about 6% of the total municipal solid wastes in 2018 [5]. Around 14% of the textile wastes were recycled, where almost 71% went to landfills for disposal. Another 15% were utilized in energy recovery by incineration with other solid wastes. Only about 4% of recycled solid wastes are from textile sources, even though textile products have almost 100% recyclability [5,7]. The data shows that sustainable waste management of textile waste needs to be explored thoroughly. In the U.S., to counter the impacts of overconsumption of textiles and frequent changes in fashion trends, recycling or reusing textile wastes will save resources and minimize environmental change. This review aims to evaluate the current sustainable approaches adopted by the U.S. in textile waste management. The article explores the textile reuse/ recycle trends in the U.S. Understanding the present scenario of textile waste management in the U.S. will enable the development of more sustainable approaches to reduce the impact of increasing textile waste on the environment.

Textile Waste Scenario in the U.S

With the enhancement of the living standards of the increased global population, apparel consumption also rises worldwide. In developed and developing countries, fashion industries now simulate the idea of new fashion trends for each season [8]. As a result, the fashion diffusion curve is becoming transient for each style, sustaining only one season. Like the mass adoption of each style, the obsoletion of each trend is becoming more rapid in frequency. As a result, the apparel production cycles are becoming shorter- increasing the production rates significantly to support the increased demands of transient fashion trends. The textile industry generates production waste throughout the manufacturing processes, affecting the environment. Moreover, the apparel product lifecycle generates textile waste in pre- and post-consumer stages. Unutilized and thrown-out textile products can be identified as pre- and post-consumer textile wastes.

Depending on the apparel’s manufacturing process, the production wastes could be of many types [6,9]. The productionwaste generation continues throughout the apparel production, including raw materials such as cotton, yarn. Water, chemicals used in the fiber, yarn, and fabric treatment contribute to the textile production waste. Cellulose fiber such as cotton, protein fiber such as wool, or synthetic fiber such as nylon requires different chemical and physical treatments. The wastes generated from these treatments could be identified as wastewater containing the discarded water with chemicals, pesticides, insecticides, or fertilizers [10]. Wastewater composition from fiber production includes pesticides, fertilizers, scouring agents (natural fibers), and petroleum oil, pigment, dyes (synthetic fiber) [10]. Yarn to fabric production generates chemical wastes from sizing chemicals, lubricants, bleaching agents, mercerizing agents, desizing chemicals, oxidative agents, dyes, pigments, and other chemicals for additional functional properties: fire retardancy, antibacterial properties, or water-resistance [10]. Solid wastes from the production process include spinning waste, fabric cutoffs, fabric roll ends, fabric defects, woven and knit cutting waste [6,11,12]. The utilization of production waste has its importance in the U.S. However, in recent years, textile and apparel production has shifted significantly from the U.S. Compared to 2009, textile manufacturing dropped from $18.79 billion to $9.5 billion in 2019 [13]. Approximately 98% of the apparel is imported [2]. So, in the U.S., the priority on production waste utilization has shifted to postconsumer waste management [14]. A change in textile production has been observed recently where special fabrics such as protective clothing, medical textile, nonwoven contributed to more than 34% of the U.S. textile export in 2021 [13]. Also, the U.S. is one of the leading exporters of cotton supporting 35% of the global cotton demands [15]. So, production waste management still needs to be monitored to counter the risk of such waste.

Pre-consumer wastes are unsold or damaged retail products yielded from design mistakes, fabric faults, wrong color production, or fail-to-sale products [12,16]. A general estimation is that 70% of the apparel production is sold, leaving 30% unsold stock [17]. In actual practices, this type of waste is mainly utilized by nonprofit organizations in donation, manufacturers in recycling the source materials, and retailers in other markets via consolidators or jobbers. So, these wastes are not actually unutilized or thrown out. Only a very small portion of pre-consumer waste is thrown out to landfills by retailers [18]. About 65% of the initial input of the global textile supply chain can flow through clothing manufacturers to the consumers as the final products, whereas 35% of the input turns into textile wastes in the production and pre-consumer stages [4].

Wastes from the post-consumer stage generate from the utilized textile materials, which lost their utility to the consumer and deiced to be thrown out. Consumers decide to throw out the textile articles when they are worn out, damaged, outgrown, or become outdated [6]. As in most cases, throwing out of the articles means accumulating new products or vice versa; the post-consumer waste amount can be comparable to the fiber consumption rate of textile production [9]. So, it can be inferred that the amount of post-consumer waste is similar to the production and pre-consumer waste amount [9]. Every year the amount of thrown-away textile is around 30 kg per person [19]. Though the reusability of such products is high, most of such wastes either go into municipal waste or are incinerated. In the U.S., thrown out post-consumer waste utilized in the landfills amounted to around 10.5 million tons per year, surpassing 350,000 tons in the U.K. and 287,000 tons in Turkey [4]. In 2019, postconsumer textile waste generated around 16.89 million tons of waste, covering approximately 6.3% of municipal solid waste [20]. Among these 16.89 million tons of waste, about 16.05 million tons (95%) were suitable for recycling [21]. However, only 2.57 million tons were subjected to be recycled, leaving most of the parts to be utilized in combustion and landfills [21]. In the socio-economic aspects of the U.S., the determinants of post-consumer waste amount generation are income range, education, accessibility to clothing stores, and residential segregation [22-24]. People living in higher accessibility of education and high-income areas generate more textile waste than people living in other regions [22,25]. High racially segregated regions and more accessible clothing stores also positively impact waste generation [22]. Such determinants highlight the apparel overconsumption tendency resulting from fast fashion.

‘Fast Fashion’ can be defined as the quick response of fashion retailers to the everchanging consumer demands [6]. In such a retail model, the products reach customers within a few weeks from the product development stage. In contrast to the traditional six months production timeline, popular clothing retailers are now adopting a 3-9-week production timeline [6]. As a result, fast fashion trends are currently generating about 52 micro-seasons dedicated to specific styles per year. In contrast, there were only four seasons in the traditional fashion cycle (pre-fall, fall, pre-spring, spring/ summer) [26]. For example, leading fast-fashion retailer ‘Zara’ generates around 12,000 styles per year [6]. Low-quality textile products are used to generate the sale inventory to support the high pace of bulk production while considering cost reduction and profit maximization [27]. Such poor material choice and low price encourage consumers to discard the previous textile article and acquire new trends [28, 29]. As a result, overconsumption and thrown-away culture generated from fast fashion is now contributing to a significant amount of post-consumer waste in the U.S. Pre-consumer and production wastes are also increasing globally due to the high production rate and fast fashion market share.

Impacts of Textile Wastes

The environmental and societal issues surrounding textile wastes begin at the very beginning of the textile supply chain. Production and utilization of textile articles generate waste throughout the production, pre-consumption, and post-consumption stages. With the increase in apparel consumption, the wastes generated from this sector are affecting the global environment and resource management. As there are no structured waste disposal procedures to address the textile wastes, such wastage points out the inefficient global resource management, affecting the environmental and social footprint. Due to the increased apparel consumption, textile wastes are now affecting the environment and the socio-economic aspects of surrounding communities more drastically than before.

The apparel production process impacts the environment through water usage, carbon or greenhouse gas emission, and energy consumption. Followed by the oil and petroleum industry, the textile manufacturing industry is the 2nd most polluting sector around the globe, responsible for 20% of the total carbon emission around the world [2,21]. If the current growth of the textile sector persists, it will be responsible for 26% of the global carbon budget by the end of 2050. By 2050, the textile sector will be utilizing 300 million tons of nonrenewable raw material, where 22 million microplastics will be released to the ocean [29].

At the preliminary stages of textile production, a large amount of water, fertilizer, pesticides, and other chemicals are used for fiber sourcing. The chemical treatments vary throughout the manufacturing process depending on the fiber types (natural, regenerated, and synthetic). A greater portion (around 63%) of consumed textile fibers comes from petrochemical or synthetic polymer sources. Synthetic fibers production requires many chemicals, and the process absorbs more energy than natural fiber production, consequently raising the global CO2 emissions [30,31]. Cotton is the most widely used natural fiber. It takes around 5,300 gallons of water to produce just 2 pounds of cotton [2,32]. Global cotton production single-handedly utilizes 44% of the total water usage [32]. In addition to this, the high rise of apparel consumption leads to increased demand for textile fibers. More cotton farms are being established by sacrificing forests to yield high cotton production. Every year around 70 million trees are being cut down to support the increased demand for textile products [2]. Chemical fertilizers, pesticides, and irrigation techniques are being utilized to increase the cotton farms’ yield. Therefore, soil infertility, desertification, and water pollution are observed in the surrounding areas [2,33]. A prominent example of such could be the Aral Sea in Central Asia. The Aral Sea has been completely drained and dried up largely due to cotton production and has caused many problems for surrounding communities [2]. Supporting the commercial production of protein fibers from animals (wool, angora, cashmere) requires large grazing fields, significantly impacting land erosion and carbon emissions [34].

The later stages of textile production contribute to environmental pollution even more. At the dyeing, washing, and drying phases of textiles production, a huge amount of wastewater generates, containing different dyes and chemicals [35]. The wash phases of synthetic textiles also generate microplastics that pollute water and food [36]. The energy consumption and corresponding carbon emissions of the fabric and apparel production process are also huge for the application of highly efficient industrial machines [37,38]. Washing of one jeans pair could release carbon quantity equivalent to driving 69 miles [3].

Pre- and post-consumer wastes thrown out as landfills or openair dumps also severely impact the environment [39]. Accumulation of landfill sites destroys natural habitats for the animals [40]. Decomposition of post-consumer wastes releases greenhouse gases such as methane, CO2, and chemical leachates. In the case of open-air dumping, the probability of chemical leachates escaping into waterways is high, which significantly affects human and animal health [41-43]. Such scenarios are much more common in developing and underdeveloped countries as often they don’t have advanced municipal waste management systems [44].

With the introduction of “Fast fashion,” overconsumption and throwaway culture are now prevailing. To meet the high demands of the new fashion products, retailers often ignore the manufacturers’ production capability. To meet the retailers’ supply demands, manufacturers often disregard the workers’ needs. Workers at the manufacturing end are often exposed to chemicals, fiber dust, and noise. Long working hours in those environments with repetitive working steps affect the mental and physical state of the workers [45]. Low payment rates, child labor, are also not uncommon in the global textile supply chain [3]. Though top retailers often conduct audits to ensure work and environmental safety at the manufacturing ends, the presence of the production subcontractors often remains outside of the audit purview [4]. For high production demand, manufacturers often have to employ subcontracting agencies, who often ignore basic workers’ rights [4]. Aside from these, the dumping sites of the textile wastes are often placed near underdeveloped regions, marking the environmental injustice as throwaway culture predominantly persists among highly educated and well-to-do communities [22].

The wastes generated from different steps of the global textile supply chain and after consumerism affect the world environment. In the global textile supply chain, the U.S. is one of the primary suppliers of raw materials like cotton, synthetic fibers. Commercial apparel production is not primarily based in the U.S., and most of the consumed textile products are imported. However, the U.S. is one of the leading manufacturers of functional clothing like protective clothing, medical textiles, and smart textiles. The U.S. textile exports have seen a 14% growth from 2010 to 2019 in special fabrics and yarns [13]. Production processes of such special textile products need to be monitored to categorize the waste generated. Consumption of imported textile products has also been increased due to the introduction of ‘Fast fashion.’ ‘Fast fashion’ associated high production rate is sacrificing the material quality, resulting in poor aging of textile articles. As a result, the U.S. has seen a 100% increase in the amount of thrown-away clothing in the last 20 years [46]. Most of such wastes find their way to landfills. Addressing such an increasing quantity with ‘Reuse’ or ‘Recycle’ will reduce the post-consumer textile waste and the supply-demand. As a result, the textile industries’ impact on the global environmental footprint can be controlled with higher efficiency. Such an approach marks the ‘Circular textile economy,’ contributing to control the resource management of the global textile supply chain. An integrative approach by fashion retailers, manufacturers, government, and consumers will surely minimize textile waste’s environmental and societal impact [4]. A structured textile waste management system adopted by the U.S. will solve the municipal solid waste problem and contribute to forming the sustainable global textile supply chain.

Textile Waste Management

The ‘Environmental Management System’ (EMS) has been introduced to promote sustainability in the textile supply chain [47,48]. ISO 14000 has been proposed to set up the rules and standards identifying the degree of the textile industry’s impact on the environment [10]. To control the environmental impact of textile waste, ‘Waste management’ has been incorporated in the EMS. ‘Waste Management’ refers to the steps taken to minimize waste generation. ‘Textile Waste Management’ aims to reduce waste generation, control environmental impact, and minimize resource input by promoting ‘Recycle’ or ‘Reuse’ in the textile products’ lifecycle (production, pre-consumer, and post-consumer) [10,49]. Textile wastes can be categorized into wastewater and solid waste based on their physical attributes. Wastewater is the effluent of the textile production processes, whereas solid wastes are the fiber, yarn, fabric, and apparel wastes thrown out in production, pre-consumer, and post-consumer stages [10]. So, ‘Textile Waste Management’ can be classified as wastewater management and solid waste management.

Wastewater management

Wastewater contains washed-away chemicals of textile production processes, oil, grease, and other particulate matters. Wastewater management refers to treating the effluents to reduce the chemical concentration and remove harmful substances before disposal to control the environmental impact. Treatment of the effluents could be categorized into physical, chemical, and biological processes [10]. Physical treatments are adopted to remove floating, suspended particulates from the wastewater. Such treatments refer to the utilization of screened filters of different fineness to filter out the particles. Mechanical flocculation and membrane filtration can also be adopted in the physical treatments of wastewater. Mechanical flocculation utilizes mechanical stirring to generate the floc of small, suspended particles. Membrane filtration can also remove some dyes along with the particles but is not economical due to the clogging and displacement risk of the membranes. Aside from the mentioned treatments, treatment via electron beam radiation has been seen to reduce the COD value of the wastewater [10,50]. Chemical treatments aim to adjust the pH value of the wastewater, reduce the COD, and decolorize it. Discoloration of the textile wastewater is achieved by adding neutralizing agents of multivalent cations and coagulation/ flocculation agents to separate the suspended particles. Ozonation, Fenton reaction (hydrogen peroxide and ferrous ion treatment) neutralizes toxic chemicals where chemicals like Aluminum sulfate, Poly-aluminum chloride, and poly-ferrous sulfate are used as coagulation/ flocculation agents [10,51-54]. Biological treatment is another alternative to treat wastewater and could be used in combination after physical and chemical treatments. Biological treatments help remove finishing agents and dye substances from the wastewater. Enzymes or microorganism cells are used in biological treatments. In the case of fungal treatment (Pleurotus ostreatus, Gloeophyllum odoratum, and Fusarium oxysporum), monoculture shows better results than co-culture treatment in dye removal [55]. Application of enzymes such as Lacasse can also be found efficient to remove certain types of dyes [56,57]. Mild operating conditions, larger space, and longer time to process wastewater make biological treatment a less favorable option for wastewater treatment [58]. The utilization of biodegradable materials (mangrove bark as dyes, bee wax, enzyme, and aloe vera as finishing agents), less harmful chemical agents (H2O2/O3 instead of chlorine bleaching agents) in the textile production process will reduce the detrimental impact of wastewater effluents. Such an approach marks the prevention of harmful waste generation [59-62]. Aside from previously mentioned treatments, textile wastewater could yield value-added products such as biogas and biohydrogen. Studies have found that biogas generation effectively reduces COD value in wastewater [63- 65]. Gasification of textile wastewater could be utilized to yield synthetic gases, which could be applied to generate electricity [66,67].

Solid waste management

With the increase in textile product consumption, solid waste from textile sources is also increased significantly in the last 20 years. With the conventional textile solid wastes handling systems, most of the wastes found their way into the municipal solid waste stream. Due to the lack of suitable facilities to manage the huge municipal waste stream, many such wastes are used as landfills or incinerated. Solid waste management aims to optimize waste generation or waste utilization via reuse, recycling, and energy recovery to counter the impact of the increasing textile consumption on solid waste generation. Textile Solid waste management could be categorized into the disposal, energy recovery, recycling, reuse, and prevention, arranged from least environment-friendly to best [6]. Conventional textile solid waste management refers to the disposal of textile wastes which mostly go to the landfills. Increased municipal solid wastes mark the lack of proper waste management facilities, expanded landfill sites to dispose of the increased share. In the landfills, synthetic solid wastes do not decompose, while the organic (wastes generated from natural or regenerated fiber products) wastes decompose but yield CH4 and CO2 [6]. Energy recovery refers to generating energy by incineration, gasification, or anaerobic digestion of textile wastes. Incineration takes up almost 90% of the textile wastes to generate flue gases (CO2, H2O, O2, N2), which can be utilized as fuel energy [68]. Though the incineration process generates harmful gases and leaves burnout wastes, emission control, energy recovery, and suitable facilities to discard the wastes can impart sustainability [68]. Gasification refers to the partial oxidation of organic compounds at higher temperatures (500 °C- 1800 °C) [68]. With the application of combined cycle gas turbines, such a process has higher efficiency in generating electric energy due to better thermal energy optimization [67]. Anaerobic digestion utilizes microorganisms to convert the organic wastes into biogas which could be utilized in green energy production. The residuals of such treatment could be used as fertilizer also [69,70]. Recycling means reprocessing the textile wastes into another useful material via combined operation of sorting, separation, and processing [71]. Textile solid wastes could be turned into raw materials of production processes or value-added end products, called downcycling and upcycling, respectively [6]. Recycling processes can be categorized into mechanical, chemical, thermal, and combined recycling processes [6]. Mechanical recycling shreds the textile waste items previously sorted based on color and quality [72]. Resultant shredded wastes can be converted to yarn or fibers, can be used as insulative materials, raw materials of nonwovens manufacturing, filling materials for mattress or upholstery, carpet underlays, or disposable diapers/napkins [6,72-74]. Chemical recycling is best suited for synthetic fiber wastes. Wastes from synthetic textiles can be converted into new yarn or fabricated into new woven, knitted, nonwoven, and composite products via chemical processes like polymer-depolymerization [75]. Other applications of such recycled synthetic fibers include household items, automobile carpeting, sound absorption materials, insulation materials, and toys [6,75]. Thermal recycling mainly refers to the pyrolysis of textile wastes. Textile wastes can be converted into synthetic fibers generating byproducts like CH4, H2, CO2 [6]. Based on the fiber resin, the pyrolysis temperature could vary between 450 °C and 700 °C. Synthetic fibers yielded by such a process can sometimes result in high-valued carbon activated fibers due to the resin carbonization [76]. Reuse means reutilization of the textile article for the same purpose it has been conceived [77]. Instead of throwing out, reusing a textile product will generate less waste throughout the whole textile supply chain. Reusing the article minimizes the products’ environmental footprint. Reusing 1 kg of textile products saves 6000 L of water, 3.6 kg less CO2 production, 0.3 kg of chemical fertilizer, and 0.2 kg less pesticide utilization [78]. So, the reuse of a textile product contributes to less waste generation, minimizes energy utilization in that products’ supply chain. Textile articles can be sold as secondhand clothing, cleaning cloths, or as vintage fashion articles after proper collection and sorting based on their conditions and antiquity [71]. Prevention refers to promoting awareness against waste generation. In the present ‘Fast fashion’ era, consumers, retailers, and manufacturers should be informed how textile wastes are affecting the environment and society. Building awareness will encourage the reuse of textile products, recycling the thrown-out articles, and facilitating the proper collection, sorting, and processing of textile wastes even at the consumer level [6,79].

Textile waste management reality in the U.S

Regarding the textile mill effluent or wastewater management, the U.S. Environmental Protection Agency (EPA) complies with the limitation guidelines and standards listed in chapter 40 of the U.S. Code of Federal Regulations contained in part 410 (40 CFR part 410) [80,81]. Based on the regulations, EPA adopted the National Pollutant Discharge Elimination System (NPDES)- a permit program to regulate the guidelines and standards of ‘40 CFR part 410’ [81,82]. Most textile mills utilize publicly owned treatment works (POTWs) to treat the wastewater. More than 14,000 POTW facilities are currently operating across the U.S. [83]. Such wastewater is generally discarded into the POTW without any prior pretreatments. As a result, POTWs have developed their local limit of essential pollution parameters to check whether the wastewater discharge adequately follows NDPES compliance [84]. EPA biennially publishes Effluent Guidelines Program Plan to review the guidelines and standards. In the recently released Preliminary Effluent Guidelines Program Plan 15 (September 2021), EPA has announced to conduct a study of per- and polyfluoroalkyl substances (PFAS) discharge from landfill and textile manufacturers [85]. According to EPA, most textile mills currently are not being monitored in terms of PFAS discharge [80]. The U.S. Environmental Protection Agency (EPA) published data regarding textile solid waste management in the U.S. [5]. Available data measures the municipal textile solid waste generation, amount of textile wastes used in landfills, energy recovery, and recycling purposes. It can be seen that after the booming of fast fashion in the 90s, textile waste generation has increased. Even though textile waste recycling has increased, landfill remains the prevalent method of textile waste management. On average, the U.S. generates approximately 16 million tons of textile waste per year, recycles only 15% of the wastes leaving almost 65% in the landfills [5]. EPA estimates that textile wastes cover approximately 5% of all the landfill space in the U.S [5]. Even though 95% of the textile wastes are recyclable, landfill is still the preferred option for textile solid waste management [21]. The challenges of textile recycling are largely relevant to the quality and characteristics of textile wastes. The utilization of solid textile wastes depends on the efficient sorting of the wastes [86]. Proper sorting and separation of the wastes based on the fiber/yarn types, colors, and apparel systems determine the recycling process or reusability. The absence of a structured textile waste collection system makes the sorting and separation process harder, given the increasing quantity of municipal solid waste. The lack of identified end-users of recycled textile raw materials impedes promoting commercial incentives for textile recycling [86]. The following waste generation data only considered the thrown-out textiles, leaving the reused textile products (Table 1).

Table 1:Textile solid waste management data (in millions of U.S. tons) [5].

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The textile resale market has seen growth in recent years in the U.S., much similar to the global market. In 2019 the global secondhand clothing market share was $28 billion [87]. Whereas, in 2018, it was $24 billion, and in 2017 it was $20 billion [87]. In 2020, the market share decreased to a value of $27 billion due to the pandemic compared to 2019. However, observing the current trends in 2021, it has been predicted that the value will rise to $77 billion in the next three years [87]. The monthly domestic secondhand retail sales are more than $1.25 billion on average, where the predominant buying trend is preowned clothing [87]. The U.S. is also one of the leading exporters of secondhand clothing. In 2019, the U.S. trade value of exported secondhand clothing was approximately $737.7 million, which is expected to rise due to the increasing global demand for reused textile products [87]. The reuse and resale of textile articles are currently increasing due to the build-up of sustainability awareness. The pandemic-affected economic condition is also encouraging the reuse tendency as less than 3% of the household budget now goes into buying clothes [87].

The change in the waste generation scenario in the current pandemic situation is also needed to be considered. The utilization of personal protective equipment has become the norm in the high propagation stages of covid-19. As a result, the production and utilization of face masks, gloves, protective suits, safety boots have substantially increased- most of which are of limited usage and thrown out after single or several usages. Such waste sources have a high potential to exacerbate the solid waste management system. Moreover, most of the PPEs (Personal Protective Equipment) are made of synthetic fibers such as polypropylene, polystyrene, polycarbonate, polyethylene, or polyester [88]. Mismanagement of the thrown-out PPEs results in such wastes being in landfills or seas [89]. During 2020-2021, total mismanaged plastic waste amounted to 8.4 million metric tons around the globe- 6% of which came from North America [90]. PPEs have contributed to 7.6% of the total mismanaged waste- amounted to approximately 0.64 million metric tons [90]. PPE production also includes specific chemical processes based on the service and materials. So, the production process of PPEs could have significant impacts on the textile effluent composition. The dynamics of textile waste generation can change due to the high disposal rate of PPEs. So, it is necessary to address the impact of Covid-19 on textile waste generation to create a fruitful waste management structure.

Conclusion

The dynamics of textile consumption is changing due to the fast-fashion trends and ongoing pandemic situation- contributing to making the textile products’ lifecycle shorter. As a result, global textile waste generation has also increased significantly. Being one of the leading importers of textile finished products and exporter of textile raw materials, the U.S. is also currently observing a higher rate of textile waste generation. The increased amount of textile waste has seen to impact the environmental condition and social lives around the textile supply chain entities. To counter the negative impacts, it is necessary to address textile waste management in a sustainable way. Such management has two dimensions- wastewater management and solid waste management. Federal regulations exist for wastewater treatment, but textile solid waste management still remains voluntary. Solid waste management largely depends on the effective collection, separation, and processing of the waste stream- making it difficult to approach the recycling and reuse of textile products. A structured waste management system will facilitate such sorting/ collection procedures and reduce the amount of solid waste disposed to landfills. A comprehensive waste management system will also consider wastewater treatment- generated from the textile supply chain. To establish an effective textile waste management structure in the present condition, the followings are some of the current concerns needed to be considered by the U.S.

• Detailed studies regarding the wastewater composition discharged from the functional textile production plant are needed to be performed. Functional clothing such as PPEs’ production process needed to be monitored to identify the discharged wastewater composition. As wastewater is being treated in POTW facilities, wastewater pretreatment requirements before discharging to POTW need to be inspected.

• It is necessary to consider the viability of imposing recycling mandates at local and state levels to establish an effective textile waste management system, considering the current transient lifecycles of textile products (PPEs, face masks, fast fashion articles).

• Studies are required to establish smooth and effective transitions of textile solid waste materials from consumer, retailer, and producer to the recycler. To facilitate the preprocesses (sorting, separation, collection) of recycling, an effective waste collection, and management structure needed to be developed. Applicability of developing a clothing labeling system to communicate recycling instructions to the consumer needed to be explored.

• Production capacity of the recycled textile raw materials needs to be expanded to establish the recycling facilities as constant and convenient suppliers to the manufacturers. Such relevant studies will promote the utilization of recycled textile raw materials.

• Viability of multiple uses of PPEs and face masks should be investigated. In this regard , the efficiency of sanitization techniques such as UV exposure and washing should be studied to promote the reuse of PPEs. Specific fabric coating or utilization of specific synthetic threads could potentially impart reusability to the PPEs.

• Market study regarding secondhand and vintage clothing can promote the reuse of textile products. If the leading retailers find it economically profitable as per their business policy, a circular model of the textile economy can be easily established.

It can be said that textile waste management does not only minimizes the generation of wastes but also optimizes the environmental and social footprint. In the present day, sustainability is not an option but rather a necessity. Given the high consumption of textiles in the U.S., an effective textile waste management system also has the potential to turn into a revenue-generating industry.

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