Benchmarking of key performance factors in textile industry effluent treatment processes for enhanced environmental remediation | Scientific Reports

Scientific Reports volume 14, Article number: 26629 (2024) Cite this article

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This article presents a comprehensive benchmarking analysis of merit performance factors in the Effluent Treatment Plants (ETP) of the textile industry. The study aims to identify and evaluate key factors that contribute to the efficient operation and performance of ETPs. The performance of ETP was analyzed by valuable data gained from figures of PH, Dissolved oxygen, Dissolved solids, Suspended solids, Density, COD and BOD. The technical trends showed the deviations in the working conditions of Effluent Treatment Plant by variation in temperature. This variation is achieved by varying the settling time of wastewater in the sedimentation tank during the working process. The required dosing, plant efficiency and economic factors were taken into account. The Plant efficiency was determined to be 83.5% at normal conditions of water entering at temperature of 30°C and pressure of 1 atm along with addition of coagulants and flocculants in the wastewater. While the efficiency of the ETP plant was calculated about 88% using a Compact photometer at elevated conditions of temperature such as > 45°C, while at other temperatures the efficiency decreases significantly due to several reasons. The operating time of water treatment was decreased due to the variations in temperature of wastewater while other conditions kept constant like pressure, flow rates of water and chemicals (Polyacrylamide and Polymeric Ferric Sulfate). The usage of coagulants and flocculants at optimum conditions has been discussed in this study.

Wastewater treatment is the removal of solids from water on micro as well as macro level. The concept of water treatment arises from the enormous use of water and disposal of it after use in the form of Effluent. Industrial effluent is mostly in the form of water which contains salts, ions, micro-organisms, solids and acids1. The textile industry has effluents which consist of high PH and huge amounts of salts, dyes and chemicals in it.

Generally the Effluent treatment plant consists of three types of water treatments. Primary, Secondary and Tertiary treatment followed by advanced treatment. Usually the tertiary treatment includes the usage of coagulants and flocculants2. These chemicals are the basic feed chemicals which are introduced in pretreated water to reduce its specific undesired properties and to make it possible for secondary level consumption. The usage of these chemicals or compounds is carried out in the third portion of the plant before the clarifier. The reactivity of coagulants removes the undesired properties of the water like apparent properties. The usage of flocculants is carried out which reduces its density3.

The E.T.P Plant consists of separating screening turbines at the exit point of industrial wastewater where the initial treatment of water is done, known as primary treatment. The secondary treatment is done at a sedimentation tank where the separation of solid particles is carried out by the process of gravity separation occurring naturally. The sedimentation tank usually comprises a capacity of about 140 m3. After this secondary treatment, the water is oxidized at the oxidation tank and neutralized at the neutralization tank. Afterwards the use of coagulants and flocculants is carried out.

Coagulants are the species or ions used for treatment of water4. These are easily available in the market and are chemically stable species while having strong properties when they are introduced in the water5. The PH of water has a great effect on the coagulants while they are used in the water. The coagulants are of various types like ferrous ions, having strong positive valences and are very suitable for reactions in which the ion exchange takes place at molecular as well as on higher level6. The basis coagulant used in the laboratory as well as on industrial level in the operation plant is Polymer 808 known as Polymeric Ferric Sulfate. The polymer is present in solid form and is introduced in the water after formation of 0.01 M solution. It is a highly diluted form to meet the requirement for the treatment of water present in the dosing tank.

While this study provides valuable insights into the effluent treatment processes of a specific textile industry, its broader applicability to other industries or effluent types remains to be explored. Textile effluents are characterized by a high variability in pollutant composition, influenced by factors such as dye types, chemical additives, and production processes. To enhance the relevance of the findings, future research should extend benchmarking analyses to different types of textile industries, including those using various dyes and chemicals, as well as to other industrial sectors such as leather tanning, pulp and paper, and food processing. Additionally, comparative studies evaluating the performance of Effluent Treatment Plants (ETPs) across these diverse industries can identify commonalities and differences in treatment efficacy. This approach will help in understanding the generalizability of the current study’s findings and in developing adaptable treatment strategies that cater to a wide range of industrial effluents, thereby increasing the practical utility and impact of the research in the field of industrial wastewater management. The focus of this work is the performance analysis of coagulants and flocculants at water treatment plants by plotting the graphs of plant performance. By alternating the outer conditions of water during operation, the graphic trends fluctuate. For analyzing the operating capacities at which the plant should be operated, laboratory scale testing is very imperative.

Coagulants and flocculants are the chemicals which are most essential in water treatment and have specific properties associated with given conditions7. The flocculants are materials or compounds which have high bonding properties and are responsible for making clusters in the water8. Flocculants are commonly used to help remove suspended particles from the water. These particles can be colloidal or suspended solids that are too small to settle out by gravity or to be removed by filtration9.

The operating capacity is calculated by the difference in inflow and outflow of the plant in the re-oxidation tank and initial screening tank10. The overall or total capacity is given by the volume capacity of the oxidation tank and the size of the outflow tunnel. The oxidation tank consists of the main sludge of the system and the sludge volume index (SVI) is calculated to determine the weekly performance of the plant. It also suggests the approximate use of coagulants and flocculants in the water11. Sludge volume index is the ratio of Sludge volume in sample to the mixed liquor suspended solids of that sample12. The SVI is the key factor to determine the performance in the plant.

The choice of flocculants depends on factors such as the type of particles to be removed, the pH of the wastewater, and the required degree of clarification13. Flocculants work by causing these particles to clump together, forming larger aggregates that are more easily separated from the water. The process of clumping is called flocculation, and the aggregates are called flocs. Cationic polyacrylamide is a type of synthetic organic polymer that is widely used as a flocculant in wastewater treatment plants14. It is derived from polymerization of acrylamide and cationic monomers such as diallyldimethylammonium chloride (DADMAC)10.

The cationic polyacrylamide has a positively charged cationic group that makes it effective in flocculating negatively charged particles such as colloids, organic matter, and suspended solids in wastewater15. Polyacrylamide is particularly useful in treating industrial wastewater from sources such as paper mills, food processing plants, and textile factories16.

After addition of 0.05 M solution of polyacrylamide in water, the wastewater is gently stirred or mixed by introducing high frequency air in it. This process encourages the formation of flocks. It helps to create larger, heavier flocs that can settle more easily. Once the reaction occurs, flocs are formed from solids present in water. The flocs settle in a sedimentation bath present below the clarifier. The flocs settle down under the influence of gravity, and the clarified water is then removed from the top. Pre-polymerized inorganic flocculants solution is prepared with varying basicity ratios, initial concentrations, addition rates, initial metal concentrations, aging time, and aging temperature17. Because of the highly specific properties of the polyacrylamide, the best formulation for its usage needs to be determined at laboratory level18. PAM can also react with anionic compounds, including surfactants, proteins, and DNA, due to the electrostatic interactions between the cationic polymer and negatively charged groups on these compounds12.

Analytical instrumentation deployed for parameter quantification within the study included a portable Hanna meter HI98197 (Accuracy: ±0.2% of the reading Precision: ±0.1% of the reading) for Total Dissolved Solids (TDS) and pH determination, complemented by a Checktemp@1 Digital thermometer HI98509 (Accuracy: ±0.2 °C, Precision: ±0.1 °C) for precise temperature assessment. The quantification of Mixed Liquor Suspended Solids (MLSS) entailed meticulous experimental procedures, employing laboratory balances to ascertain the respective weights.

For Chemical Oxygen Demand (COD) quantification, the instrumental apparatus selected was the Macherey Nagel Compact photometer (PF‑12 Plus) Accuracy: ±1% of the measured value, Precision: ±0.5% of the measured value. Biochemical Oxygen Demand (BOD), an integral parameter in this research, was quantified through a 5-day BOD test, conformed to specified temperature conditions, employing the Hach BODTrackII100 apparatus (Accuracy: ±0.1 mg/L for BOD measurements Precision: ±0.05 mg/L). Supplementary laboratory-scale equipment and instrumentation encompassed ovens, furnaces, precision weight balances, desiccators, digesters, and an assortment of analytical apparatus, each tailored to cater to the exigencies of the respective analyses and processes.

In the application of coagulants and flocculants, these chemical agents were judiciously diluted with aqueous media to optimize their performance within the treatment regime. The selected flocculant, Cationic Polyacrylamide (PAM), was procured from Shouxin, characterized by CAS No. 9003_05_08, and denoted by its synthetic organic polymer composition, bearing a distinctive white appearance. Complementary to this was the deployment of Polymeric Ferric Sulfate as the designated coagulant, sourced from YUANBO, distinguished by CAS No. 10028_22_05, and exemplified by its inorganic high polymer nature, typified by a red-brown appearance. Neutralization of the wastewater matrix necessitated the introduction of concentrated 98% Sulphuric Acid, sourced from SensoTech, characterized by a density of 1.840 g/cm3, and strategically employed as the neutralizing agent.

As an indispensable adjunct to the treatment process, Chloroform, identified by CAS No. 64-17-5, was utilized as an antifoaming agent. This essential chemical constituent was procured from J.K. Enterprises, thereby contributing to the effective mitigation of foam generation within the treatment system, ensuring operational stability and precision in experimental outcomes.

To ensure sustainable water treatment practices, it is imperative to evaluate the environmental impact of the chemicals used in the effluent treatment process, specifically polyferric sulfate (PFS) and polyacrylamide (PAM). These chemicals, while effective in coagulation and flocculation, may leave residuals in the treated water, potentially affecting aquatic ecosystems and human health. Future research should focus on assessing the persistence and toxicity of these residuals, employing advanced analytical techniques to quantify their concentrations in treated effluents. Additionally, exploring alternative eco-friendly coagulants and flocculants, or optimizing the dosages of PFS and PAM to minimize residuals, can contribute to more sustainable treatment practices. This comprehensive approach will help in developing strategies that not only achieve high treatment efficiency but also mitigate adverse environmental impacts, aligning with the goals of sustainable industrial wastewater management.

The water treatment plant, boasting a volumetric capacity of 1000 m3/day, serves as an indispensable facet of the textile industry, dedicated to the maintenance and enhancement of water quality. The plant operates with an inlet flow rate spanning the range of 20–30 m^3/h, necessitating the utilization of a robust infrastructure to effectively cater to the influx of raw wastewater. Within this intricate system, pivotal components include an oxidation tank with a volumetric capacity of 250 m^3, a clarifier boasting a volumetric capacity of 100 m^3, and an essential chemical dosing tank with a volumetric capacity of 50 m3.

Chemical dosing is executed with meticulous precision, involving the induction of turbulence within the wastewater matrix. This perturbation is diligently achieved by harnessing the influence of air injection, facilitated by the Three-Stage Ring Blower apparatus operational at a frequency of 50 Hz, expertly manufactured by GOORUI. The performance evaluation of the treatment plant is intricately entwined with the precise determination of chemical concentrations employed for the augmentation and purification of the water under examination, notably at two distinct temperatures: 30 °C and 45 °C.

The inflow of water, derived from the effluent originating from the textile dyeing house, enters the sedimentation tank at an elevated temperature range of 60–65 °C. This unique environmental milieu, marked by an increased temperature regime, mandates careful consideration. The sedimentation tank offers a temporal respite of three hours for the requisite attenuation of this water inflow, given its characteristic elevated temperature. Post-retention time, the treated water is conveyed to the neutralization tank, a crucial juncture in the treatment process where pH modulation is effectively executed. This pH adjustment endeavor necessitates the judicious introduction of sulphuric acid into the neutralization tank. The confluence of this pH-adjusting agent with the wastewater is synchronized with the concurrent introduction of air, strategically driven at a frequency of 50 Hz through the deployment of blowers.

Subsequently, the treated water, having undergone neutralization, progresses to the oxidation tank, wherein further purification and remediation are orchestrated. The chemical dosing tank, a pivotal component following the oxidation tank, is meticulously designed to accommodate and facilitate the judicious application of decoloring agents and flocculants. The specified chemicals employed in this process encompass coagulants, specifically polymeric ferric sulfate (PFS), and flocculants, in the form of polyacrylamide (PAM). Notably, the tank serves as a reservoir, not only for these critical chemical species but also for pH adjustment agents, such as sulphuric acid, and, most crucially, the intricate amalgamation of the chemicals with the wastewater matrix.

The meticulous orchestration of this elaborate treatment process underscores its significance in achieving water quality goals within the textile industry. The harmonious interplay of the aforementioned units, bolstered by precise chemical dosing and rigorous performance assessment, is essential in upholding the industry’s commitment to environmental stewardship and regulatory compliance, particularly under conditions characterized by variable temperatures and the introduction of diverse chemical constituents.

Subsequent to the judicious infusion of coagulants and flocculants into the aqueous medium, the treated effluent is meticulously channeled towards the clarifier unit. The distinct functionalities of the clarifier manifest in a stratified manner, with clarified water ascending towards the upper echelon while the denser sludge component gravitates towards the lower tier of the sedimentation basin. This clarifier-generated, pristine water effluent subsequently traverses towards the reoxidation tank, while the sludge fraction, amassing within the confines of the clarifier, is systematically translocated to the dedicated sludge return tank through a purpose-built pumping mechanism.

The operational equilibrium pertaining to sludge content within the oxidation tank is perpetuated through a controlled regimen, where the consistent introduction of sludge from the sludge return tank is orchestrated, a process meticulously executed until an established and predetermined threshold of Sludge Volume Index (ranging from 80 to 100) is attained. This equilibrium is instrumental in preserving the requisite microbial biomass and enzymatic activity essential for the degradation and biotransformation of organic constituents within the wastewater matrix.

The clarified water, now suitably refined within the reoxidation tank, is channeled towards the effluent treatment plant outlet, culminating in its intended discharge. Systematic sampling protocols are diligently observed throughout the experimental timeline, capturing water specimens at discrete intervals from each designated process unit. The collected samples are subsequently subjected to rigorous analytical scrutiny, facilitating the quantification and characterization of a comprehensive array of parameters, including Dissolved Oxygen (DO), Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Total Suspended Solids (TSS), Total Dissolved Solids (TDS), Mixed Liquor Volatile Suspended Solids (MLVSS), pH levels, and temperature attributes. This analytical orchestration is conducted using specialized instrumentation, precisely detailed in the methodological apparatus. The comprehensive data acquisition is fundamental to the in-depth elucidation of the treatment process’s efficiency.

Process flow diagram of ETP plant installed at textile site of required research.

The water is entered into the initial screening where most of the suspended visible impurities are removed initially. The screened water is moved towards the sedimentation tank while the flow rate is measured by using a flowmeter FIT-01 (Fig. 1). After the retention time, the water is moved towards the neutralization tank by three submersible pumps G01-A, G01-B and G01-C manufactured by Shanghai Pacific Pumps with 60 m NPSH capacity, Single-phase version: 220–240 V, 50 Hz. After the addition of 98% commercial scale H2SO4 in wastewater, its PH gradually decreases to about 7.5. As shown in Fig. 1 of E.T.P plant. The chemical dosing is done after the retention time which is the key principle of water treatment and imparts great effect in the performance of plants. The initial temperature of water is about 60°C to 70°C. Greater is the sedimentation time, lesser will be the temperature. Therefore, the control of temperature is dependent on sedimentation time9.

The primary focus within the domain of wastewater treatment pertains to the mitigation of temporary hardness, an issue fundamentally instigated by the presence of synthetic organic dyes originating from the wastewater specimens inherent to the textile industry. The existence of these synthetic organic dyes introduces a substantial potential for environmental contamination within the extensive network of water channels and reservoirs, emblematic of the industrial expanse in Lahore, Pakistan. As a consequence, a crucial preliminary step necessitates the strategic extraction of these pernicious organic entities, effectuated through the judicious application of coagulants.

Exemplary analysis of the wastewater effluents, conducted following a labor-intensive 9-hour operational shift, illuminated a remarkable phenomenon characterized by the gradual decrement in Total Dissolved Solids (TDS). This decrease was distinctly marked, culminating in a reduction equivalent to one-fourth of the initial concentration, prominently manifesting upon the introduction of Polymeric Ferric Sulfate (PFS) into the aqueous milieu.

Figure 2 denotes the trend of TDS at outlet water while addition of Ferric Sulfate.

Total dissolved solids (TDS) profile with initial conditions: T = 32 °C, P = 1 atm, Q = 25 m3/h, PFS = 0.01 M.

The concentration of TDS decreases due to decolorization in water caused by cationic reaction with negatively charged colloids of water and positively charged Ferric Sulfate. The reaction between polymeric ferric sulfate (PFS) and an azo dye involves the complexation of the dye with the iron species present in PFS, leading to precipitation and removal of the dye. The exact reaction mechanism and the chemical structure of the precipitate can vary depending on the specific azo dye and PFS formulation.

Azo Dye (R-N = N-R’) + Polymeric Ferric Sulfate (PFS) + Coloured water → Precipitated Complex + clean water.

In this equation, “Azo Dye” represents the azo dye molecule with its specific chemical structure (R-N = N-R’). When mixed with PFS, a complex is formed, and the azo dye is removed from the solution by precipitation as part of the solution. Upon the amalgamation of polymeric ferric sulfate with the aqueous wastewater matrix, a subsequent introduction was affected involving a solution of polyacrylamide (herein constituting a concentration of 0.05 moles per liter, denoted as 0.05 M).

In the intricate interplay of chemical reactions between azo dyes named as Synozol K-HL and introduced chemical constituents, the transformation of molecular structures unfolds through a series of bond breakages and novel molecular formations. This intricate chemical metamorphosis exerts a profound influence on the behavior of Zeta ions within the system, elucidating the multifaceted interplay of charge interactions within the aqueous milieu. The pivotal addition of coagulants into the aqueous medium catalyzes the enthralling and fundamental reaction cascade, ultimately culminating in the cleavage of azo bonds, a transformation of paramount significance. A definitive manifestation of this transformative process is the discernible diminishment in the vibrant and often intense coloration characterizing the azo dye-infused wastewater, an intriguing phenomenon represented visually in the illustrious Fig. 3.

Reaction mechanism of Synozol K-HL with PFS at following conditions: P = 1 atm, Q = 25m3/h.

Concomitantly, the molecules of Polymeric Ferric Sulfate (PFS) deftly engage in dynamic interactions with the azo dye molecules, thereby facilitating the extrication of the deleterious constituents from the wastewater matrix.

Upon a meticulous dissection of the architectural configuration presented within Fig. 3, an intricate tapestry of chemical events unfurls in a chronological sequence encompassing three distinctive and interrelated stages. The initial phase of this complex cascade encompasses the concerted breakage of azo dye bonds, marking a pivotal point in the deconstruction of these organic moieties. As the process progresses, the second stage delineates the selective removal of R-SO2 bonds, a step meticulously designed to disentangle the azo dye structure, thereby liberating it from its former chemical moorings. Finally, the third and concluding phase in this intricate procession signifies the surgical excision of the -R group, the very essence of the azo dye’s structural identity. This removal eventuates in the establishment of robust molecular bonds between the liberated azo dye constituents and the industrious molecules of Polymeric Ferric Sulfate (PFS), an emblematic manifestation of the dynamic interplay witnessed within the treatment system.

As this series of molecular transformations transpires, it engenders a spectacular alteration in the chromatic characteristics of the wastewater, signifying the effective and precision-driven removal of the vivid colors historically associated with azo dyes. The manifestation of this progression attests to the capability of the treatment process to systematically dismantle and ameliorate the environmental ramifications associated with azo dye contaminants in textile wastewater, charting a course towards ecologically responsible and sustainable industrial practices. The inherent complexity of these reactions necessitates a detailed investigation of the involved mechanisms and kinetic parameters, underscoring the critical role of chemical dosing strategies and their potential for environmentally conscientious industrial operations.

The focal issue associated with wastewater pertains to the occurrence of temporary hardness alongside various organic compounds, primarily attributable to the introduction of synthetic organic dyes within the wastewater specimens emanating from the textile industry. Consequently, the procedural stage involves the elimination of these hazardous organic constituents through the employment of flocculants. The incorporation of polyacrylamide within the dosing reservoir catalyzes the establishment of chemical bonds between alkali metal ions prevailing within the aqueous medium, leading to their gradual precipitation and coalescence over a temporal span of nine hours. This inclusion of PFS, executed with a meticulous molarity of 0.01 M, constitutes a strategic maneuver aimed at obviating the deleterious influence of these synthetic organic dyes, thereby steering the textile industry towards an environmentally conscientious operational paradigm.

This progressive agglomeration process is recognized as flocculation. Figure 4 projects the trend of TSS in outlet water at re-oxidation tank with the passage of time during addition of chemicals in dosing tank. PAM operates in a multifaceted manner within the ETP. Primarily, it functions as a flocculant and coagulant aid, facilitating the aggregation. The polymer’s high molecular weight contribute to the formation of intricate networks, augmenting the likelihood of particle collision and subsequent agglomeration. The introduction of polyacrylamide (PAM) as a coagulant aid in the context of an Effluent Treatment Plant (ETP) represents a highly efficacious and scientifically substantiated approach aimed at the mitigation of Total Suspended Solids (TSS) within wastewater matrices. The intrinsic rationale underlying the use of PAM resides in its polymer-based structure, characterized by anionic, cationic, or non-ionic moieties. This promotes the removal of TSS by enhancing sedimentation and filtration efficiencies.

TSS profile of ETP with addition of PAM at following conditions: T = 30 °C, P = 1 atm, Q = 23m3/h, PAM = 0.05 M.

The water loses TSS by ½ of the initial concentration. This is because the electrostatic nature of PAM is leveraged through charge neutralization mechanisms. The charged groups on PAM molecules can interact with oppositely charged particles in the wastewater, reducing the overall repulsive forces and enhancing the aggregation propensity of suspended solids. This phenomenon synergizes with the coagulation-flocculation process, expediting the formation of larger, settleable flocs. The dosage and molecular weight of PAM are critical factors requiring meticulous optimization to attain optimal TSS reduction. An excessive PAM dosage may result in overdosing, leading to the resuspension of flocs, while insufficient dosing may render the treatment less effective. After the formation of flocs in solution, the densities of the clusters of solids are comparatively high which causes them to settle down in the solution.

The COD is the imperative factor which is to be determined during the addition of PAM in the water during oxidation. The purpose of the addition of polyacrylamide is to form flocks in the water which ultimately reduces its TSS along with the reduction of COD in the water 14. The Whole experiment was conducted in two conditions. In the first condition the inlet water to the chemical dosing tank was at 30 °C while in the second condition, the inlet water was at 45 °C. Both conditions show different trends. When the concentrations of these chemicals are increased beyond the specified 0.01 M for PFS and 0.05 M for PAM, several effects can be observed. Firstly, the increased concentration leads to the formation of larger flocs. These bigger flocs are heavier and settle more quickly, which can enhance the initial stages of the sedimentation process. However, there is a downside to this increase. The larger flocs can also make the water more viscous. This increased viscosity can pose challenges in the later stages of treatment, such as filtration and sludge handling, as the thicker water is more difficult to process and requires more energy and time to handle.

On the other hand, if the concentrations of coagulants and flocculants are decreased below the specified levels, the formation of flocs is significantly impaired. At lower concentrations, there are insufficient coagulant and flocculant molecules to effectively neutralize the charges on the particles in the wastewater. As a result, the particles remain dispersed and do not aggregate into flocs. This lack of floc formation means that the particles cannot be effectively removed from the water, leading to poor clarification. The water remains turbid and contaminated, as the suspended solids and impurities are not adequately separated. Figure 5 Elaborates the trend of COD calculated on laboratory scale by experimental method performed using COD vials COD-1500 and COD-750 by photometer PF-12. The COD in the sedimentation tank is about 2250 PPM while 250 PPM in the outlet water at the re-oxidation tank. According to the standards of E.P.A, the COD in outlet water to the sewage from different industries should be in a range of < 350 mg/L[2]. Here the presence of biological treatment processes, such as activated sludge or aerobic digestion is effective in reducing COD levels of water present in chemical dosing tank and in re-oxidation tank. The COD varies from oxidation tank to outlet water.

Thus, maintaining the optimal concentration of coagulants and flocculants is essential for efficient wastewater treatment. The specified concentrations of 0.01 M PFS and 0.05 M PAM are likely determined through careful experimentation to balance the benefits of floc formation with the drawbacks of increased viscosity. Deviating from these concentrations, whether by increasing or decreasing, disrupts this balance and leads to suboptimal treatment outcomes. Effective wastewater treatment relies on precise chemical dosing to ensure that flocs form appropriately, sedimentation occurs efficiently, and the treated water meets quality standards. The COD of water is reduced due to removal of organic material present in water.

COD profile in re-oxidation tank at following conditions: T = 29 °C, PFS = 0.01 M, Q = 27m3/h, PAM = 0.05 M.

The organic waste present in water is oxidized at high temperature and associated reaction between the PAC and colloidal solution. It makes bonds with the organic material present in water and settles down. The main reason for the reduction of COD is the removal of organic material from water. Figure 6 elaborates the increase in mixed liquor suspended solids MLSS in the oxidation tank at given 30°C while the pressure remains the same.

Trend of MLSS vs. Time in oxidation tank at following conditions: T = 32oC, Q = 27m3/h, P = 1 atm.

The measurement of COD in vials is carried out by taking more than one sample from the COD is reduced with the retention time when the polyacrylamide is added. The MLSS increases due to the addition of solids separated from water. Since the TDS and TSS decreased from the water which indicates that the water in the clarifier is about to clean10. While in the next phase, the conditions remain the same but the concentration of coagulants and flocculants is decreased with increase in temperature of the water and keeping the same flow rate. This can be achieved by lowering the sedimentation time in the sedimentation tank.

The readings show that the reduction in impurities take place at high levels due to the less retention time given in the sedimentation tank. While the efficiency performance of coagulants and flocculants increases at high temperature. Figure 7 shows the progression in hardness of water and PH levels when the water moves from initial to final tanks. As the inlet water of plant is of high temperature, this temperature is beneficial for the treatment process. The pre heated water is pumped into the oxidation tank where the process takes place. The water with high temperature causes the process of oxidation to proceed at a high rate. Greater is the temperature, greater is the treatment efficiency.tank and mixing them together in a flask. The COD of water is high at the initial stage in the sedimentation tank.

Trend of Hardness and PH at different tanks: T = 29oC, P = 1 atm, Q = 24m3.

The colloidal solution is negatively charged in the water while the addition of highly positive ions causes the formation of bonds between them. Hard water is generally considered to be less reactive than soft water. The next phase in which water at high temperature is used. Figure 8 is the comparative study of TDS with both operating conditions. The collective trend shows that the removal of TDS from water takes place at a high rate, when the temperature is kept high because the solution with energy takes less time.

Temperature can affect the solubility of certain contaminants in water. For example, as temperature increases, the solubility of some minerals and gasses increases. Temperature can affect the viscosity of water, which can impact the flow rate through treatment systems. The rate of TDS decreases with the influence of coagulation. The Fig. 8 explains the trend of TDS.

Comparison of TDS vs. Time in both conditions at: T1 = 32 °C, PFS = 0.01 M, PAM = 0.05 M, T2 = 45 °C.

While the same trend is present in the case of TSS of water with the addition of PFS and PAM. Figure 9. Discusses the trend of TSS with time in both conditions. Together, coagulants and flocculants can effectively remove ions from water by causing them to clump together and settle out of the water. This process is particularly effective for removing negatively charged ions such as sulfates, nitrates, and phosphates, which can be difficult to remove by other means. The effectiveness of coagulants is dependent on various factors such as the type of coagulant used, dosage, pH of the wastewater, and the nature of the particles in the wastewater. Flocculants work by increasing the size and weight of the flocs, making them easier to separate from the wastewater. The efficiency of flocculants is dependent on various factors such as the type of flocculent used, dosage, pH of the wastewater, and the nature of the flocs formed.

TSS profile in both conditions at: T1 = 30 °C, PFS = 0.01 M, PAM = 0.05 M, T2 = 46 °C.

High temperatures can increase the growth of algae and bacteria in water storage tanks and distribution systems. Temperature can impact the adsorption capacity of activated carbon filters used in water treatment. The efficiency of coagulants is determined by their ability to destabilize the colloidal particles in the wastewater. Coagulants work by neutralizing the charge of the particles, causing them to coagulate and form larger particles. The MLSS also increases at high rates as shown in Fig. 10. This is due to an increase in concentration of impurities at high temperatures.

MLSS at: T1 = 32°C, PFS = 0.01 M, PAM = 0.05 M, T2 = 43°C.

Table 1 gives the different values of minerals present in the water at initial and final treated water at both conditions. It shows the presence of dissolved ions in the treated water at the outlet tank at both temperatures. All of the values are determined at laboratory scale. The chlorine value is determined by using chloride-50 vial of NANOCOLOR by using spectrophotometer NANOCOLOR PF-12. The COD is determined by COD-1500 vial by using method ISO 985 029. The BOD is calculated using B.O.D sensor bod. F102B0133. The ammonium was calculated using Ammonium-3 vial by using ISO 985 003. Similarly sulfate and fluoride was calculated using vials. The following figure gives the brief calculations.

Upon looking into Table 1, we can confirm that the efficiency of E.T.P plant increases most with only one parameter. Water treatment processes may also rely on the activity of microorganisms to break down contaminants. Temperature can have a significant impact on the growth and activity of these microorganisms.

It also affects the rate of sedimentation in settling tanks. The formation and stability of flocs in flocculation processes is also affected by fluctuating temperature. The effectiveness of temperature can increase the corrosion rate of pipes and other equipment and ultimately can affect the performance of ion exchange systems. The PAM and PFS work best under specific pH conditions. For example, PFS works best at a pH range of 5.5 to 7.5, while PAM works best at a pH range of 4.0 to 6.0. Adjusting the pH of the water to the optimal range can significantly improve the efficiency of coagulants. To provide a more comprehensive treatment approach, future research should integrate and compare biological treatment processes, such as activated sludge, with the chemical treatments currently discussed. Biological treatments offer distinct advantages, including the breakdown of organic pollutants through microbial activity, which can complement the coagulation and flocculation provided by polyferric sulfate (PFS) and polyacrylamide (PAM). By conducting comparative studies, the synergistic effects of combining biological and chemical methods can be evaluated, potentially enhancing overall treatment efficiency and reducing chemical usage. This holistic approach can lead to more effective and sustainable effluent treatment solutions, addressing a broader range of pollutants and minimizing environmental impacts. Such integrative strategies will advance the field of textile effluent remediation, ensuring cleaner water discharge and compliance with stringent environmental regulations.

Efficiency performance of E.T.P plant at: T1 = 45°C, T2 = 30°C, P = 1 atm.

The experiments show that cationic polymers are more effective in the treatment of municipal wastewater. Several factors can affect the efficiency of coagulants and flocculants. These include the pH of the wastewater, the temperature, the concentration and nature of the pollutants, the type and dosage of coagulants and flocculants used, and the mixing intensity. The pH of the wastewater can significantly affect the efficiency of coagulants and flocculants. The optimal pH range for coagulation and flocculation is typically between 6.0 and 8.0. Outside this range, the efficiency of coagulants and flocculants may be significantly reduced. The concentration and nature of pollutants in the wastewater can also affect the efficiency of coagulants and flocculants and change in different properties. Figure 11. Shows the Efficiency of flocculants and coagulants for fluctuating the different components in water at 30°C and 45°C. The efficiency of plants, coagulants and flocculants increases as we increase temperature.

The performance of coagulants and flocculants was determined in the whole process of ETP. The addition of polymeric ferric sulfate is carried out first and then the addition of Poly Acrylamide. The water at high temperature increases the efficiency of removal of solids from water. The reaction takes place more effectively at high temperature. Hence the performance efficiency of flocculants and coagulants increases by increasing the temperature up to 45oC. However, at other temperatures, the efficiency dropped significantly. This decline at non-optimal temperatures is due to various factors affecting the treatment process. Thus, temperature plays a crucial role in determining the performance of the ETP. The use of coagulants and flocculants also impacts the efficiency, as they help in the removal of contaminants. It is recommended to check the causes of delayed treatment of water by detailed analysis. These analyses include BOD and COD levels, %age TDS and TSS contents, capacity MLSS, temperature, density, flow rates, dissolved oxygen and ions percentages. The flow rates of coagulants and flocculants should be adjusted according to Jar testing performed at laboratory level by following standards of ISO testing. The efficiency of the polymeric ferric sulfate and polyacrylamide increases about 10% by increasing the temperature. To comprehensively address the limitations of the current research, future studies should extend the scope beyond Total Dissolved Solids (TDS), Total Suspended Solids (TSS), Chemical Oxygen Demand (COD), and Biological Oxygen Demand (BOD) to include the analysis of heavy metals and specific organic compounds in textile effluents. These pollutants, such as lead, cadmium, mercury, and persistent organic pollutants (POPs), pose significant environmental and health risks even at low concentrations. By incorporating advanced analytical techniques such as Inductively Coupled Plasma Mass Spectrometry (ICP-MS) for heavy metals and Gas Chromatography-Mass Spectrometry (GC-MS) for organic compounds, a more holistic understanding of the effluent composition can be achieved. This study will be benchmarking research at industrial level which sheds light on the development of polymeric waste components for efficient wastewater treatment at industrial scale.

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The authors also would like to extend their sincere appreciation to Researchers Supporting Project number (RSPD2023R612), King Saud University, Riyadh, Saudi Arabia.

Institute of Chemical Engineering and Technology, University of The Punjab, Lahore, Pakistan

M. U. Shakeel, S. Z. J. Zaidi & A. Ahmad

King Saud University, Riyadh, Saudi Arabia

A. A.M. Abahussain

University of Southwales, Pontypridd, UK

M. H. Nazir

Laboratory for energy water and healthcare technologies, University of The Punjab, Lahore, Pakistan

M. U. Shakeel, S. Z. J. Zaidi & A. Ahmad

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Conceptualization, S.Z.J.Z. and M.U.S.; methodology, S.Z.J.Z.; validation, S.Z.J.Z., M.U.S. and A.A.; formal analysis, M.U.S; investigation, M.U.S. and S.Z.J.Z.; data curation, M.U.S.; writing- original draft prepwriting- M.U.S.; writing-review and edit, M.U.S A.A.; visualization, M.H.N.; supervision. Z.J.Zaidi; project administration, A.A.M.A. S.Z.J.Z. All authors have read and agreed to the published version of the manuscript.

Correspondence to S. Z. J. Zaidi or M. H. Nazir.

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Shakeel, M.U., Zaidi, S.Z.J., Ahmad, A. et al. Benchmarking of key performance factors in textile industry effluent treatment processes for enhanced environmental remediation. Sci Rep 14, 26629 (2024). https://doi.org/10.1038/s41598-024-72851-9

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Received: 12 May 2024

Accepted: 11 September 2024

Published: 04 November 2024

DOI: https://doi.org/10.1038/s41598-024-72851-9

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