Treatment Plant Effluent Research Articles

Acoustic cavitation for the process intensification of biological oxidation of CETP effluent containing mainly pharmaceutical compounds: Understanding into effect of parameters and toxicity analysis

The current work investigates the efficacy of acoustic cavitation (AC) based pretreatment as a process intensification method for improving the conventional biological oxidation (BO) treatment of the effluent from common effluent treatment plant (CETP) mainly containing pharmaceutical compounds. The effluent acclimatized with cow dung-based sludge was utilized for the aerobic oxidation with an optimum condition of 1:3 ratio of sludge to effluent and 6 h as duration. COD reduction of 19.58% was achieved with the conventional biological oxidation, which was demonstrated to be improved by incorporating acoustic cavitation-based pretreatment approaches under optimized conditions of 125 W and 70% duty cycle for only AC as well as oxidant loadings as 1000 mg/L for H2O2, 250 mg/L Fe(II) with 1000 mg/L H2O2 for Fenton, 1000 mg/L for KPS and 0.5 L/min for the O3 during the combination approaches. The improved COD reduction after the use of pretreatment approaches followed by the BO of 6 h duration was 29.26%, 72.42%, 85.47%, 45.68% and 69.26% for the AC, AC + H2O2, AC + Fenton, AC + KPS and AC + O3 based approaches respectively. The toxicity assay of the effluent before and after every pretreatment approach using bacterial strains ofStaphylococcus aureusandPseudomonas aeruginosaensured the biodegradability of the treated effluent as no toxic intermediates could be seen. Overall, the present work elucidated the effectiveness of acoustic cavitation-based pretreatment approaches for the improvement of conventional BO of CETP effluent.

Impact of lockdowns and possible quantification of pollution sources on the water quality of the Yamuna River

ABSTRACT The COVID-19 lockdown halted industrial and transportation networks, resulting in a change in the level of pollution. In this study, the analysis of pre- and post-lockdown water quality of the Yamuna River is done, and primary causes are identified, by considering five in situ parameters and four Landsat-8-derived parameters. During the 2020 lockdown, pollution-indicating in situ parameters decreased, with chemical oxygen demand decreasing the most, possibly due to reduced industrial impact. All satellite-derived indices improved during lockdown and post-lockdown periods of 2020. Even in segments with uniform flow, floating algal index and normalized difference vegetation index exhibited lower levels. In contrast, the examination of the 2021 lockdown revealed no noteworthy insights. Mapping the observations with the drainage network and location of common effluent treatment plants revealed that industrial effluents were the dominant cause of water quality fluctuations. This demonstrates the impact of industrial effluents on the degrading water quality of Yamuna.

Life cycle assessment of sequential microbial-based anaerobic-aerobic reactor technology developed onsite for treating textile effluent

Although biological treatment of textile effluent is a preferred option for industries avoiding toxic chemical sludge production and disposal, requirement of several extra pre-treatment units like neutralization, cooling systems or additives, results in higher operational cost. In the present study, a pilot scale sequential microbial-based anaerobic-aerobic reactor technology (SMAART) was developed and operated for the treatment of real textile effluent in the industrial premises in continuous mode for 180 d. The results showed an average ∼95% decolourization along with ∼92% reduction in the chemical oxygen demand establishing the resilience against fluctuations in the inlet parameters and climate conditions. Moreover, the pH of treated effluent was also reduced from alkaline range (∼11.05) to neutral range (∼7.76) along with turbidity reduction from ∼44.16 NTU to ∼0.14 NTU. A comparative life cycle assessment (LCA) of SMAART with the conventional activated sludge process (ASP) showed that ASP caused 41.5% more negative impacts on environment than SMAART. Besides, ASP had 46.15% more negative impact on human health, followed by 42.85% more negative impact on ecosystem quality as compared to SMAART. This was attributed to less electricity consumption, absence of pre-treatment units (cooling and neutralization) and less volume of sludge generation (∼50%) while using SMAART. Hence, integration of SMAART within the industrial effluent treatment plant is recommended to achieve a minimum waste discharge system in pursuit of sustainability.

Impacts of seasonal variations and wastewater discharge on river quality and associated human health risks: A case of northwest Dhaka, Bangladesh

Surface water pollution caused by the discharge of effluents from industrial estates has become a major concern for Dhaka (Bangladesh). This study aims to have a concise look at the severe river water pollution, mainly from effluents discharged from the tannery village. Effluent samples were collected from five ejected points, including the central effluent treatment plant (CETP), twenty adjacent river water, and two pond water nearby Hemayetpur, Savar. Thirty-one parameters have been observed at these sampling points for three seasons, from April 2021 to January 2022. The results obtained from water quality indices, i.e., water quality index (WQI), entropy water quality index (EWQI), and irrigation water quality index (IWQI), show that most studied surface water samples ranked “unsuitable” for consumption, irrigation, and anthropogenic purposes. The highest health risk was observed downstream of Hemayetpur city at the Savar CETP discharge site, indicating higher levels of heavy metal in the river water following the tannery village. Carcinogenic and non-carcinogenic human health risks could be triggered mainly by water consumption as concentrations of arsenic (As), chromium (Cr), nickel (Ni), and lead (Pb) exceeded the upper benchmark of 1 × 10−4 for adults and children. The results of the carcinogenic risk assessment revealed that children were more vulnerable to health hazards, and quick corrective action is required to control the increased levels of heavy metals at all sample locations. Therefore, through bioaccumulation, human health and the environment are affected in these areas. Using river water for consumption, household work, or even irrigation purposes is not advisable. This study's result highlighted that properly implementing compatible policies and programs is required to improve effluent treatment methods and provide biodegradability to the Dhaleshwari River.

Feasibility study of common effluent treatment plant for management of industrial wastewater: Case study of Bangladeshi textile industries

AbstractTextile industries play a vital role in the economy of Bangladesh contributing significantly to its gross domestic product. However, they are associated with high environmental pollution, especially water pollution. Since small‐scale textile industries cannot afford the treatment cost of discharged wastewater, they tend to contaminate water sources—both groundwater and surface water. To intervene in response to this situation, the existing treatment system was assessed in the present study. The effluents from industries under this research were analyzed for color, pH, TSS, TDS, chlorides, sulfates, COD, BOD, and total hardness. A Common Effluent Treatment Plant (CETP) with zero liquid discharge was suggested as a solution. It was observed that the water recovery in the proposed scheme by reverse osmosis and salt recovery using nanofiltration were 90%–95% and 80%–90%, respectively. Cost analysis also indicated that the cost of treating water can also be decreased by 18.7% which can show that water recovery is even more affordable for small‐scale industries. Finally, a linear programming model was developed to assist the industries with decision‐making in the selection of treatment schemes. This research revealed that a CETP using zero liquid discharge technology is a potential solution to the environmental crisis due to industrial wastewater discharge. This could ensure reduced water pollution, increased drinking water availability, improved public health, and thus could be a potential driver for environmental sustainability.

Chemical Investigation and Separation of Chromium from Chrome Cake of BSCIC Tannery Industrial Estate at Hemayetpur, Dhaka, Bangladesh

Leather tanning mainly depends on chrome tanning. A huge amount of basic chromium sulfate (BCS) is used in leather tanning. About 60–70% of BCS has been taken by leather and the rest of the amount is discharged as effluent and solid waste. In the Common Effluent Treatment Plant (CETP) of BSCIC Tannery Industrial Estate (Hemayetpur, Savar, Dhaka), the effluent which contained a high concentration of chromium is precipitated as solid chromium hydroxide with other elements which is called a chrome cake. Chrome cake is not exposed directly in the open space due to its toxic effect on human health as well as the environment. Human occupational experience distinctly indicates that, when inhaled, chromium compounds are respiratory tract irritants, resulting in airway irritation, airway obstruction, and lung, nasal, or sinus cancer. It is strongly suggested to extract Cr from the chrome cake before dumping it; otherwise, it will be a potential hazard to the environment. Herein, the chrome cake is characterized by inductively coupled plasma-optical emission spectroscopy (ICP-OES), X-ray fluorescence (XRF), UV-visible spectrophotometer, etc., and develops a method to separate chromium from chrome cake. ICP-OES and XRF analyses show that the total chromium contained in chrome cake is ∼17.45% and 20.7%, respectively. UV-visible spectrophotometer indicates that ∼0.04% of chromium is hexavalent. Afterward, chromium has been separated by using H2SO4 where the optimized concentration was found to be 7%. The separation efficiency of chromium from the chrome cake for optimized condition is obtained at ∼95%.

Application of response surface methodology in optimization of process parameters for combined biological treatment of dairy wastewater using consortium of bacteria and microalgae

AbstractThis study was conducted to investigate the combined two‐stage biological‐treatment‐process using consortium of bacteria and microalgae for removal of soluble chemical oxygen demand (SCOD), ammonium‐nitrogen (NH4+‐N), nitrate‐nitrogen (NO3−‐N), phosphorus (PO43−‐P) from dairy wastewater in suspended‐growth batch‐reactor (SGBR). The study also investigated the removal of SCOD, NH4+‐N, NO3−‐N, PO43−‐P under different process parameters, like initial SCOD, NH4+‐N,NO3−‐N, PO43−‐P, MLSS, pH and react time using response surface methodology (RSM) with a five‐factor‐three‐level Central Composite Design(CCD). The experimental results were analyzed by ANOVA and second‐order polynomial mathematical‐models were developed with high correlation efficiency for SCOD, NH4+‐N removal, NO3−‐N, PO43−‐P removal using bacterial and microalgal‐consortia respectively in SGBR. Individual and combined effects of process variables on responses were studied using three‐dimensional response surface plots. Under the optimum conditions (initial SCOD, NH4+‐N, pH, MLSS of 720 mg L−1, 55 mg L−1 as N, 7 and 1500 mg L−1, respectively and react time of 24 h) highest removal efficiencies of SCOD (98.61%) and NH4+‐N (97.42%) were obtained using bacterial consortium and in second‐phase using micro‐algal consortium under optimum conditions highest removal efficiencies of nitrate nitrogen and phosphorus 98.64% and 90.53%, respectively. Optimization of process‐parameters by RSM study is supposed to be helpful for the treatment of real life dairy wastewater in effluent treatment plants.

EIS capacitor sensor, with TiO2 dielectric, applied in the evaluation of phosphate in wastewater

This work presents the development of an Electrolyte-Insulator-Semiconductor (EIS) device with a built-in reference electrode to detect phosphate in wastewater. The idea of developing this device comes from the need to improve the use of water processed by the effluent treatment plant. After treatment process, a fraction of the water can be used as wastewater, this water cannot be consumed, however it can be used for other purposes including cleaning public spaces, such as streets and squares. In the fabrication process of the EIS device, titanium oxide (TiO2) deposited on a silicon substrate was used as a sensor element, and titanium nitride (TiN) was used for the reference electrode. Both materials were deposited by the reactive sputtering process. Aluminum (Al) was used for the electrode on the back of the slide deposited by evaporation. Preliminary results of structural and electrical characterizations indicate that the manufactured device has good sensitivity to phosphate ions (66 mV/ppm). This sensitivity is due to the good quality of the film, which is shown using Raman spectroscopy, atomic force microscopy (AFM) and X-ray diffraction (XRD) techniques, in addition to electrical measurements.

Sludge Management in the Textile Industries of Bangladesh: An Industrial Survey of the Impact of the 2015 Standards and Guidelines

The textile sector of Bangladesh has positively contributed to a significant impact on its national economy and employment opportunities due to its rapid growth. The increasing number of wet processing units has led to a growing amount of wastewater volume as well as textile sludge (a byproduct of wastewater or effluent treatment plants). In 2015, the government of Bangladesh instituted the “Bangladesh Standards and Guidelines for Sludge Management”. Therefore, this case study aimed to assess these standards’ impact on the textile industry’s sludge management practices, informing academic scholars of the research opportunities available, and serving as a policymaking tool for various other South Asia and Southeast Asia economies. The sludge management situation of thirty-six industries (namely, twelve dyeing, twelve printing, and twelve washing) was herein assessed through a self-administered questionnaire survey of respondents from the respective ‘Top Management’ and ‘Environmental Chemical Responsible’ (ECR) departments. Among the findings, the assessment revealed that neither treatment procedures nor reuse and recycling activities are present for sludge management in any of the studied industries. The responsible personnel from the textile industries have not undergone any level of technical training, and 41.7% of the printing industries still dump sludge in the open environment. The majority (83%) of stakeholders are unaware of the dangers and potential effects of improper sludge treatment. The key factors—responsibility, knowledge, behavior, and consideration—analyzed in this study, together with the study’s recommendations, will be a vital step forward in formulating policy advocacy for hazardous sludge management within the textile sector of Bangladesh.

Treatment and disposal practices of pharmaceutical effluent containing potential antibiotic residues in two states in India and perceptions of various stakeholders on contribution of pharmaceutical effluent to antimicrobial resistance: a qualitative study

BackgroundAntimicrobial resistance (AMR) is a looming pandemic, demanding prompt actions to avert catastrophic consequences. Effluents from pharmaceutical industries containing antimicrobial residues could serve as one of the entry points of these drugs to the environment. This qualitative study explores the treatment and disposal practices of pharmaceutical effluent (PE) containing potential antibiotic residues (ARs) by interviewing major stakeholders. In addition, we assessed their knowledge and perception on contribution of PE to AMR.MethodsThe study was conducted in the two Indian states, Haryana and Telangana and at the federal level. Data was collected by semi-structured in-depth interviews of 29 participants from 17 stakeholders/organizations viz. Central Pollution Control Board (CPCB), State Pollution Control Boards (SPCBs) of Telangana and Haryana, civic body, pharmaceutical manufacturers, pharmaceutical associations and civil society. Data was analyzed using thematic analysis.ResultsThe effluent treatment and disposal practices varied with the multinational companies (MNCs) having advanced technologies whereas the small and medium-scale pharmaceutical companies (SMPCs) having effluent treatment plants as per the regulations but often under-utilized. The presence of ARs in the PE was considered inconsequential by SPCBs and SMPCs and majority of stakeholders imputed other causes as major contributors to AMR. However, the MNCs were well aware of the contribution of PE to AMR and CPCB also considered ARs as direct source of AMR. The central regulators as well as MNCs expressed concerns regarding the current regulations lacking maximum ARs in the PE.ConclusionSetting up regulatory standards for maximum ARs in PE, their implementation and monitoring is an urgent need to curb environmental contribution of ARs to AMR. The findings of our study will help in systematic approach in policy making, awareness programs and capacity-building in dealing with the ARs in PE to combat AMR.

Experimental analysis on consumption of manufacturing waste in road construction and its environmental effects

All over the world, there has been a crisis of exploiting the natural resources for the development of surrounding environment in aid of construction industry. Also, it has been noted that, due to the technological boom, the waste accumulation has also been in a very huge proportion which is capable of causing serious environmental effects. Hence, an attempt is made to utilize the dumped waste has a replacement in road industry, which has made a greater impact0 with high prospects. The waste material that we have considered is copper slag from the unit situated at Tuticorin, Tamil Nādu, India, which generates 2600 tons of copper slag per day. In this industry, the copper slag waste after the treatment has been dumped in and around the land premises available at the industry itself due to insufficient utilization and also 10 to 20 tons of dry sludge is produced per day from the existing common effluent treatment plant. Hence in this research work, we recommend to use these waste materials over the construction of road through the evaluation of their required properties such as Physical and Chemical. The waste sample materials are tested for the determination of geotechnical characteristics by mixing them with the local clayey soils in the range of 25% to 75%. The probability of using these mixes in the sub grade of road pavement was studied in a detailed manner by conducting laboratory tests. The possibility of replacing the fine aggregate with copper slag in bituminous slag has been investigated. It was concluded that copper slag cannot be individually used as a sub base material. By means of conducting the necessary laboratory test, due to the dumping of slag around the premises causing environmental effects are evaluated and from which it has been identified that heavy metal concentration were in lower ratio than the pollution limits. The detailed technical specification over the design of utilizing the expected waste at the road pavement are discussed along with their data generated through the tests.

Persistence of Heavy Metals in River Sirsa Around Industrial Hub Baddi, India.

The Indian riverine system has become dumping site for toxic industrial pollutants. For assessing the flow of pollutants at various trophic levels, it is primarily important to do elemental profiling first so as to detect their load in Sirsa tributary of river Sutlej flowing through foothills of Shivalik in Himachal Pradesh, around the industrial hub Baddi, Solan. The study area includes three observation sites (S1, S2, and S3) on river Sirsa and drainage system of Baddi industrial units; the Effluent Nallah as demarcated in figure1. Heavy metal concentrations in water samples were detected using inductively coupled plasma mass spectroscopy of elements (Ti, V, Cr, Co, Ni, As, Li, Cd, Cs, Pt, Pb, Hg) as these were found to be very common in effluents of chemical, cement, textile dyeing, electronics and pharmaceutical industries. Statistical analysis showed that the concentrations (ppb) of elements found to be within permissible limits of WHO at sites under study for seven metals (Hg, Li, Ti, V, Co, Cs, Pt) but it was higher for five toxic heavy metals (Cr, Ni, Pb, As, Cd) at S2 only, streamlined in order Cr >Ni > Pb> As >Cd >Hg >Li >Ti >V >Co > Cs > Pt. It may be due to improper installation of common effluent treatment plant (CETP) on the bank of river Sirsa or due to leakage by tanker carrying waste water from various industrial set ups as these units were not directly linked to CETP. These sites were committed to act as ultimate gutter to receive all types of industrial pollutants as part of mismanagement. The load of Arsenic and Lead is increasing in lotic region and its impact on aquatic ecosystem at trophic level can be explored to combat toxicant pollution.

Assessment of Wastewater Quality Discharged from Common Effluent Treatment Plant (CETP) and its Impact on Irrigated Soil around Jajmau, Kanpur, India

Assessment of Wastewater Quality Discharged from Common Effluent Treatment Plant (CETP) and its Impact on Irrigated Soil around Jajmau, Kanpur, India

Antineoplastic drugs in environmentally relevant concentrations cause endocrine disruption and testicular dysfunction in experimental conditions

5-fluorouracil (5-FU) and methotrexate (MTX) are among the most widely consumed antineoplastic drugs worldwide. These drugs are known as emerging pollutants, once after consumption are excreted by feces and/or urine in a mixture of compounds and metabolites, entering the aquatic environment due to low efficiency in drug removal by effluent treatment plants. Considering that these substances may interact with the DNA, causing metabolic and morphological changes, leading to cell death, the present study aimed to investigate the potential impact of a long-term exposure to these antineoplastic drugs in environmentally relevant concentrations, on testicular morphophysiology of rats. Male Wistar rats (70 days old) were distributed into 4 groups (n = 10 / group): control, received only vehicle; MTX, received methotrexate at 10ngL−1 in drinking water; 5-FU received 5-fluorouracil at 10ngL−1 in drinking water; and MTX+ 5FU, received the combination of MTX and 5-FU at 10ngL−1 each. The treatment period was from postnatal day (PND)70 to PND160, when the animals were euthanized for evaluation of testicular toxicity and changes in endocrine signaling. In these experimental conditions, both drugs acted as endocrine disruptors causing cytotoxic effects in the testes of exposed rats, altering the structural pattern of seminiferous tubules and leading to oxidative stress even at environmental concentrations.

Characterization of Tannery Effluent and Efficiency Assessment of Central Effluent Treatment Plant (CETP) at Savar in Bangladesh

The industry discharges a large volume of effluent, many of which contain lots of chemicals and toxic substances that have the potential to cause distress to the environment. The study focused on analyzing various physicochemical parameters of the effluent discharge from the Central Effluent Treatment Plant (CETP) at the Savar Tannery Industrial Zone. The effluent was collected four times (pre-monsoon, monsoon, and post-monsoon) a year, from 2021-2022. The effluent was inspected for vital water quality parameters, such as pH, COD, BOD, TDS, TSS, NO3-, SO42-, HCO3-, PO43-, Cl-, Na, Ca, Cr, Fe, Cu, Zn, and Pb. Most of the parameters exceed the standard permissible limit of the Department of Environment, Bangladesh (DoE, BD), NQES, and ISW-BDS for inland water. The mean concentrations of COD, BOD, TSS, and Cr were 337, 97.5, 209, and 6.1 mg/L, and these values were far above the permissible limit with a removal efficiency of 51%. The study observed that industrial discharge of unproperly treated effluent deteriorates the surface water quality and causes huge threats to aquatic life and sustainable water resource management.

Characterization and Removal Efficiency of Central Effluent Treatment Plant (CETP)

Tannery industries are one of the most pollution-generating industries in the world. Tannery wastewater is usually characterized by high BOD, COD, TDS, and TSS and a high percentage of dissolved organic and inorganic matter. The central effluent treatment plant (CETP) of industry plays a vital role in sustainable industrial waste management and saves different lives from harmful effects. The study aimed to analyze various physicochemical parameters of the composite tannery influent and effluent as well as the removal efficiency of the CETP of the Savar Tannery Industrial Zone in Bangladesh. It was carried out at Savar Upazila, situated in the northwest part of Dhaka, Bangladesh. The samples were collected three times (pre-monsoon, monsoon, and post-monsoon) in a year, from monsoon 2021 to pre-monsoon 2022. The major water quality parameters for the influents and effluents included pH, BOD, COD, TDS, TSS, NO3-, SO42-, HCO3-, PO43-, Cl-, Na, Ca, Cr, Fe, Cu, Zn, and Pb. Most of the parameters, especially BOD, COD, TDS, and TSS after treatment, exceeded the standard permissible limits of effluent discharge prescribed by the ISW-BDS-ECR (1997), DoE-BD, and NEQS (2000), and these values were two times higher than the permissible limit. The DO value was four times lower than the permissible limit, indicating heavily polluted water. The concentration of the cations in the tannery effluents was in the following order: Na>Ca>Cr>Fe>Cu>Zn>Pb. The analysis results illustrated that the overall removal efficiency of the CETP was about 47%. The study observed that the performance of the CETP was not satisfactory, and hence it needs further improvement in the treating capacity for sustainable industrial wastewater management.

Studies in nanofiltration of dyes industry effluent

ABSTRACT A large number of chemicals are being produced in the industries, which resulted in accumulation in the effluent stream. The impact of these effluents on the environment is very adverse, if it released directly without treatment. Nowadays, the treatment of the effluent before discharge is very important due to strict norms imposed by various government agencies. In our study, the effluent from a local effluent treatment plant (effluent from dyes factory) was procured and treated with hydrophilic polymeric and ceramic nanofiltration membranes. The membrane characterisation was done based on flux, permeability, flux recovery ratio, and flux decline ratio. The effluent received from ETP and treated effluent was characterised in terms of pH, total dissolved solids (TDS), Chemical Oxygen Demand (COD), Conductivity, Turbidity, and Osmolality. From our experimental study, more encouraging results were obtained. More than 50% COD reduction was observed in the process. The membrane flux was recovered by the physical (by using backwashing) and chemical process (by using sodium hypochlorite solution). The different range was used for optimising the appropriate process for recovery of membrane flux. About 95% membrane flux was recovered by physical process on both ceramic and polymeric membranes.

Adsorption isotherm, kinetics and response surface methodology optimization of cadmium (Cd) removal from aqueous solution by chitosan biopolymers from cephalopod waste

The present investigation was aimed to explore the cadmium removal efficiency, mechanism and characterization of Chitosan biopolymers from cephalopods waste. The extracted chitosan has showed good yield of 32% and with high minerals, ash and moisture content. In the Fourier-transform infrared spectroscopy (FT-IR) analysis multiple active functional groups of Amine, Amine, Hydroxyl were found between 612 and 3424 cm−1 and the sugar signals such as N-acetyl glucosamine (GlcNAc) and H-1 [GlcN (H-1D), GlcNAc (H-1A)] were identified in Chitosan by 1H Nuclear Magnetic Resonance (NMR). The Crystalline, rough surface, micropores characters were observed in Chitosan surface by Scanning Electron Microscope (SEM) analysis and the pores played a key role in adsorption process. The Cd ions removal was performed by batch experiment and the results were revealed that the pH, temperature, time and dosage highly influenced the process and the optimum condition was discovered through RSM for pH 7, temperature 42.5 °C, time 220 min and dosage of sorbent 1 g/L respectively. The kinetics models of the Cd removal were carried out and the results revealed that the Pseudo-second order is more suitable and fit for removal than Pseudo-first order model. Chitosan surface characters and functional groups played a big role in adsorption process and Chitosan can be alternative eco-friendly, low cost and highly efficient sorbent for heavy metal removal in effluent treatment plants.

Isolation and identification of naturally occurring textile effluent-degrading bacteria and evaluation of their ability to inhibit potentially toxic elements

Untreated textile dye-contaminated wastewater contains potentially toxic elements (PTEs) and causes pollution when discharged. Herein, we attempted to isolate and identify naturally occurring effluent-degrading bacteria and investigate their resistance potentials against various PTEs. Wastewater samples were collected from the biological effluent treatment plant of a textile dyeing industry located at the Chattogram Export Processing Zone, Bangladesh. The effluent samples contained Pb and Cr, with 27 times higher Cr content than the regulatory limit. A total of 14 bacterial isolates were isolated from the effluent based on differences in their cultural properties. Based on morphological and biochemical features, isolates were identified as Staphylococcus xylosus, Bacillus korlensis, Pseudomonas fluorescens, Pseudomonas cichorii, Brevundimonus diminuta, and Enterococcus columbae. Isolates were primarily screened for their ability to reduce the content of PTEs, such as Cr, Pb, Mn, Cu, and Cd. Pre-incubation of effluents and isolates revealed that most bacteria reduced the PTEs in the effluent. Of the 14 isolates, six exhibited potential in reducing most of the PTEs—Cd (94–99%). Further, Cr was decreased by 68 and 61% in the presence of S. xylosus and P. fluorescens, respectively, after 72 h of incubation in a medium containing 400 mg L−1 salt. The findings of this study can provide insights into the efficient biological remediation of PTEs in industrial wastewater.

Pretreatment of Slaughterhouse Effluent Treatment Plant Sludge Using Electro-Fenton Process for Anaerobic Digestion

Sludge management is an integral process of an effluent treatment plant (ETP). This study aimed at using the electro-Fenton (EF) process for pretreatment of a cattle-based slaughterhouse ETP sludge to enhance biogas production from anaerobic digestion. EF-oxidation experiments were conducted in 0.5 L beakers with mild-steel electrodes, to study the effect of factors, viz., H2O2 concentration, current density and reaction time on soluble chemical oxygen demand (sCOD) concentration, soluble extracellular polymeric substances (sEPS) concentration and volatile suspended solids (VSS) removal efficiency. This was followed by the quantification of biogas production from the raw and pretreated sludge in anaerobic digestion (AD). Experimental conditions for the EF process were optimized using response surface methodology (RSM). At optimized experimental conditions, EF pretreatment resulted in an increase in sCOD and sEPS concentrations, from 0.91 g/L to 6.1 g/L and 0.18 g/L to 1.4 g/L, respectively. VSS removal efficiency was 68.1%. Batch anaerobic digestion studies demonstrated an enhancement in the specific biogas yield, from 110 NmL/g-VS to 460 NmL/g-VS.