Advanced Biological Treatment Research Articles

Research progress and perspective on sludge anaerobic digestion technology: A bibliometric analysis.

Rational disposal of sludge is an ongoing concern. This work is the first attempt for in-depth statistical analysis of anaerobic digestion (AD) research in recent three decades (1986-2022) using both quantitative and qualitative approaches in bibliometrics to investigate the research progress, trends and hot spots. All publications in the Web of Science Core Collection database from 1986 to April 4, 2022 were analyzed. Results showed that the research on AD started in 1999 and the number of papers significantly increased since 2012. The research about the disposal of sewage sludge mainly focuses on energy recovery (e.g. methane and short chain volatile organic acids) by AD. Besides, different pretreatment technologies were studied in this study to eliminate the negative effects on the disposal of sludge caused by hydrolysis (rate-limiting step of AD), water content (increasing the costs) and heavy metal (toxic to the environment) of sludge. Of those, the treatment technologies related to direct interspecies electron transfer were worth further studied in the future. Towards that end, iron conductive material, iron-based advanced oxidation and biological treatment were concluded as the prospective technologies and worth to further study.

Evaluating the environmental and economic performance of biological and advanced biological wastewater treatment plants by life cycle assessment and life cycle costing.

The primary objective of this study is to assess and establish benchmarks for environmental and economic sustainability of biological and advanced biological wastewater treatment plants (WWTPs) with different treatment technologies and characteristics. Furthermore, the study aims to determine the beneficial role of WWTPs to reduction of eutrophication potential. Environmental and economic sustainability of ten municipal WWTPs was assessed using life cycle assessment (LCA) and life cycle costing (LCC). In the first section of the study, LCA was performed to determine the environmental performance of the WWTPs. Furthermore, net environmental benefit (NEB) approach was implemented to reveal the beneficial role of WWTPs to eutrophication potential. In the subsequent section, LCA-based LCC was conducted by integrating the results of LCA. The most significant environmental impact was determined as marine aquatic ecotoxicity, which is highly affected from the generation and transmission of electricity consumed in the WWTPs. Wastewater recovery and co-incineration of sewage sludge in cement kiln ensure significant environmental savings on ozone layer depletion, human toxicity, acidification, photochemical oxidation, and abiotic depletion (fossil fuel) potential. Considering NEB approach, the highest NEB values were found for the WWTPs with the higher organic load and nutrient concentration in the influent. The results of LCC in WWTPs varied between 0.21 and 0.53 €/m3. External (environmental) costs were evaluated higher than internal (operational) costs for all selected WWTPs. While eutrophication was the highest among environmental costs, electricity cost was the highest among operational costs for almost all WWTPs.

Effects of Hydrothermal Pretreatment and Anaerobic Digestion of Pig Manure on the Antibiotic Removal and Methane Production.

Whether advanced biological waste treatment technologies, such as hydrothermal pretreatment (HTP) integrated anaerobic digestion (AD), could enhance the removal of different antibiotics remains unclear. This study investigated the outcome of antibiotics and methane productivity during pig manure treatment via HTP, AD, and HTP + AD. Results showed improved removal efficiency of sulfadiazine (SDZ), oxytetracycline (OTC), and enrofloxacin (ENR) with increased HTP temperatures (70, 90, 120, 150, and 170°C). OTC achieved the highest removal efficiency of 86.8% at 170°C because of its high sensitivity to heat treatment. For AD, SDZ exhibited resistance with a removal efficiency of 52.8%. However, OTC and ENR could be removed completely within 30days. When HTP was used prior to AD, OTC and ENR could achieve complete removal. However, residual SDZ levels reduced to 20% and 16% at 150 and 170°C, respectively. The methanogenic potential showed an overall upward trend as the HTP temperature increased. Microbial analysis revealed the antibiotics-induced enrichment of specific microorganisms during AD. Firmicutes were the dominant bacterial phylum, with their abundance positively correlated with the addition of antibiotics. Methanobacterium and Methanosarcina emerged as the dominant archaea that drove methane production during AD. Thus, HTP can be a potential pretreatment before AD to reduce antibiotic-related risks in manure waste handling.

Application of machine learning algorithms and feature selection methods for better prediction of sludge production in a real advanced biological wastewater treatment plant

Although the management of sewage sludge is an important and challenging task of wastewater treatment, there is a scarcity of studies on the prediction of waste sludge. To overcome this deficiency, the present work aims to develop an appropriate model providing accurate and fast prediction of sewage sludge. With this aim, different machine learning (ML) algorithms were tested by data obtained from a real advanced biological wastewater treatment plant located in Kocaeli, Turkey. In modelling studies, a data set from January 2022 to December 2022 composed of 208 daily measurements was considered. The flow rate of the plant (Q), polyelectrolyte dosage (PD) and removed amounts of total suspended solids (TSS), chemical oxygen demand (COD), biological oxygen demand (BOD), total phosphorous (TP), total nitrogen (TN) were assigned as input parameters to predict sludge production (SP). The precision of the models was evaluated in terms of Mean Square Error (MSE), Mean Absolute Percentage Error (MAPE), Root Mean Square Error (RMSE), Mean Absolute Error (MAE), and correlation coefficient (R2). Among the various tested models Kernel Ridge Regression provided the best accuracy with R2 value of 0.94 and MAE value of 3.25. Mutual information-based feature selection (MIFS) and correlation-based feature selection (CFS) algorithms were also used in the study in order to enhance the model performance. Thus, higher prediction accuracies were achieved using the selected subset of features. Furthermore, importance contribution of features were calculated and visualized by SHapley Additive exPlanations (SHAP) technique. The overall results of the work indicate the feasibility of ML models for describing the dynamic and complex nature of SP. The process operators may benefit from this modelling approach since it enables accurate and fast estimation of sewage sludge by using fewer and easily measurable parameters.

Microplastics in advanced biological wastewater treatment plant of Kocaeli, Turkey: point source of microplastics reaching Marmara Sea

Microplastics in advanced biological wastewater treatment plant of Kocaeli, Turkey: point source of microplastics reaching Marmara Sea

The water footprint assessment for advanced biological wastewater treatment plant

The water footprint assessment for advanced biological wastewater treatment plant

Enhanced ammonia nitrogen and phenol removal by immobilized bacteria through composite mycelium pellet-driven quinone redox cycle

The composite mycelium pellet (CMP) was coupled with Pseudomonas sp. Y1 (CMP-Y1) to remove phenol and ammonia nitrogen (NH4+-N). The CMP was formed by the self-assembly of fungal mycelium with sponge iron (SIO), gallic acid (GA), and oxalic acid. The results showed that CMP with abundant pore size and successful internal loading of sponge iron containing iron nanoparticles. CMP could induce GA redox cycle to form Fenton-like reaction and thus achieve efficient phenol removal (93.32%, 24 h). Meanwhile, the removal efficiencies of phenol, NH4+-N, and chemical oxygen demand (COD) using CMP-Y1 at 12 h were 93.71, 92.40, and 89.00%, respectively. The increase in the electron transfer activity of strain Y1 by the addition of CMP could facilitate the nitrogen removal processes. In addition, high-throughput sequencing results indicated the abundance of antioxidant and repair genes was increased, which might be a strategy of strain Y1 to cope with oxidative stress. This strategy provided the possibility for the practical application of the combination of advanced oxidation and biological treatment, and offered new insights into the symbiotic system of fungi and bacteria.

Research Progress of Industrial Heavy Metal Wastewater Treatment Process

With the rapid development of modern industry, the types and emissions of heavy metal wastewater are also increasing day by day. Heavy metal wastewater is non biodegradable, and discharge standards are also updated and iterated with people's continuous requirements for health. Based on the current situation of industrial heavy metal wastewater treatment in China, this paper summarizes the sources and treatment status of heavy metal wastewater, as well as the commonly used technologies and processes for industrial wastewater treatment from traditional to modern at home and abroad, introduces the advantages and disadvantages of physical, chemical and biological treatment methods for industrial wastewater containing heavy metals in practical applications, and looks forward to the development trend of Advanced oxidation process and biological treatment methods. The biological treatment method has the characteristics of rich raw materials, environmentally friendly and pollution-free, but at present, the research on biotechnology is not mature and its application is not widespread. If the system is applied to industrial treatment of heavy metal wastewater, further research is still needed. There are few heavy metal wastewater treatment equipment or systems developed from heavy metal wastewater treatment processes, and the issues of continuous operation, automation, and large-scale treatment of heavy metal wastewater still need to be explored. There is also room for development in the field of resource development and utilization by extracting and recovering heavy metals from sludge after heavy metal wastewater treatment. This article reviews the methods for treating heavy metal wastewater and evaluates them, with the aim of pointing out research directions and providing practical application references for the large-scale industrial development of industrial heavy metal wastewater in the future.

Synthesis of Nickel Oxide Impregnated Activated Carbon and Application for the Photocatalytic Degradation of Methylene Blue Dye under UV Irradiation

The Wastewater treatment process is an increasing serious challenge for the whole world. Due to this reason, the proficient treatment of wastewaters has attracted major attentions among researchers to solve the problem. Several methods for removal of the dye contaminants from wastewater including photocatalytic degradation, adsorption, coagulation/flocculation, advanced oxidation processes, ozonation, membrane filtration and biological treatments have been developed and use. Amongst which, photocatalytic degradation has been recognized as the most popular treatment process in aqueous solution with the advantages of high efficiency and simple operation. In the past two decades, photocatalytic degradation of organic pollutant by semiconductor oxide such as TiO2, ZnO, NiO, SnO2, Cu2O, and In2O3 has attracted due to their high photo-catalytic efficiency, low cost and low toxicity, high physical and chemical stability, especially, strong ability of fully decomposing organic pollutant into harmless species. In the present work, NiO nanoparticle were synthesized by a chemical precipitation method using nickel nitrate as precursors and Sodium hydroxide as precipitating agent. The NiO nanoparticles have been successfully used as a photocatalyst for degradation of Methylene Blue dye from the aqueous medium. The synthesized nanoparticles were studied by powder XRD, EDAX, UV and FTIR spectroscopy. The powder XRD result revealed that the obtained sample structure. The particle size and the morphology of NiO nanoparticles were studied by the SEM. The EDAX and FTIR analyses confirmed the formation of NiO nanoparticles. Further, NiO impregnated activated carbon (AC-NiO) was prepared for photocatalytic degradation studies. The Photocatalytic degradation study results revealed that the AC-NiO nanocomposite was potential photocatalyst in degradation of Methylene blue (75%) when compared with plain Nio (25%).

Fate and removal of pesticides in solid and liquid phases of metropolitan, urban and rural-scale wastewater treatment plants

In this study, the change of occurrence, distribution, seasonal variation and removal of pesticides, atrazine (ATZ), chlorpyriphos (CPR) and chlorfenvinphos (CFV), were investigated both in liquid and solid phases of three different types of wastewater treatment plants (WWTPs). Treatment configurations of the studied WWTPs consist of a metropolitan advanced biological treatment system (4-stage Bardenpho), urban-scale waste stabilization pond (WSP) and rural-scale horizontal subsurface flow constructed wetland (HSSCW).ATZ removal efficiencies (59.8 %–92.4 %) were higher than CPR and CFV removal efficiencies at all WWTPs. CPR and CFV are removed at 78.5 % and 53.1 % efficiency, respectively, from the influent of advanced biological treatment system. CPR and CFV removals were 21.6 and 22.7 % at WSP, respectively.One of the important findings is that ATZ and CFV were removed at higher percentages in primary treatment than in biological treatment in advanced biological WWTP. Sorption onto sludge has been evaluated as an effective removal mechanism for pesticide elimination, at least as much as biodegradation/biotransformation. All investigated pesticides were detected in higher concentrations in primary sludge (168.8–399.5 μg/kg) compared to secondary sludge (21.9–146.3 μg/kg) in advanced biological WWTP and in facultative sludge (447.8–1044.7 μg/kg) compared to anaerobic sludge (250.0–613.0 μg/kg) in WSP. It was determined that ATZ was the most treated compound in the liquid phase under anaerobic conditions among the studied pesticides. In line with these results, approximately 45 % removal efficiency was determined for CPR and CFV in the anaerobic digestion process present in advanced biological WWTP.

Removal of emerging contaminants in conventional and advanced biological wastewater treatment plants in India-a comparison of treatment technologies

Emerging contaminants (ECs) are a growing concern for the environment and human health. The study investigates 20 commonly reported ECs in 10 wastewater treatment plants (WWTPs) in urban to semi-urban settlements of north India over two years in the summer and winter. The selected plants were based on waste stabilization pond (WSP), up-flow anaerobic sludge blanket (UASB), activated sludge process (ASP), anoxic-aerobic process (AO), anaerobic-anoxic-oxic process, biodenipho process, sequencing batch reactor, and densadeg-biofor process. Of the 20 ECs, all 20 were identified in the influent and effluent, and 13 were identified in the final sludge on at least one occasion. The concentration in the influent, effluent, and sludge varied in the range from 2.5 ng/L to 77.4 μg/L, below limit of detection (LOD) to 1.984 μg/L, and < LOD to 1.41 μg/g, respectively. Acetaminophen and caffeine were predominately detected in the influent, whereas naproxen, ciprofloxacin, and carbamazepine were predominant in the effluent. The total removal in the plants was found in the range of 40.3–68.6%, mainly attributed to biodegradation/biotransformation. Removal of ECs by WWTPs, ranked by a relative removal criterion, followed the order: Biological nutrient removal based plants > WSP > UASB > densadeg-biofor > AO > ASP > combitreat-SBR. The risk assessment showed the risk to algae from antibiotics and triclosan, daphnia from triclosan, and fish from triclosan and hormones.

Potential of food waste-derived volatile fatty acids as alternative carbon source for denitrifying moving bed biofilm reactors

Fossil-based materials such as methanol are frequently used in the denitrification process of advanced biological wastewater treatment as external carbon source. Volatile fatty acids (VFAs) produced by anaerobic digestion of food waste, are sustainable compounds with the potential to act as carbon sources for denitrification, reducing carbon footprint and material costs. In this study, the effectiveness of food waste-derived VFAs (AD-VFA) was investigated in the post-denitrification process in comparison with synthetic VFA and methanol as carbon sources. Acetic acid had the highest rate of disappearance among single tested VFAs with a denitrification rate of 0.44 g NOx-N removed/m2/day, indicating a preferential utilization pattern. While AD-VFA had a denitrification rate of 0.61 mg NOx-N removed/m2/day, sVFA had a rate of 0.57 mg NOx-N removed/m2/day, indicating that impurities in AD-VFA did not play substantial role in denitrification. AD-VFA proved to be promising carbon source alternative for denitrification in wastewater treatment plants.

UV/iodide advanced reduction process and biological treatments to ofloxacin photo-degradation and mineralization: influence parameters, kinetic, degradation pathway, energy consumption and toxicology

ABSTRACT The degradation of ofloxacin (OFL) by ultraviolet (UV) radiation in the presence of iodide was studied as an advanced reduction process (ARP), and followed resulting effluents were biodegraded for further mineralisation in the biological treatment. About 100% degradation of OFL was obtained under the selected condition (OFL: Iodide molar ratio of 2:1 and pH 9.0) after 20 min reaction time. In UV/Iodide ARP, the obtained range for reaction rate constant (k obs) and reaction rate (r obs) were from 0.311 to 0.039 min−1, and from 15.55 to 7.94 mg/L.min, respectively. The calculation of the energy consumption (using kinetic model) indicated with increasing OFL concentration from 50 to 200 mg L−1, the amount of energy consumption increases from 0.905 to 7.09 kW per cubic metre of treatment (also it was observed increase from 0.91 to 6.29 kW per cubic metre of treatment using IUPAC model). Intermediate (I) products and possible photodegradation pathways of OFL in the UV/Iodide ARP effluent were analysed after 30 min using GC-MS. Investigations showed after 30 min, most of the intermediates were converted to simple linear compounds such as acrylic acid (I6: C3H4O2), formic acid (I9: CH2O2) and acrylaldehyde (I10: C3H4O), that finally mineralised to CO2, H2O, NH4+ and NH3. Modified Kirby-Bauer disc diffusion test (applied to investigation of bacterial inhibition) was reduced from 33 mm (in initial concentration of OFL without treatment) to 9 mm (after 30 min of reaction). The UV/Iodide effluent reduced the COD by 40.9% after 30 min of reaction. When the biological reactor as post-treatment was operated at a concentration of MLSS 1000 mg L−1, the COD removal efficiency reached to 65.28% (121 to 42 mg L−1) within 11 h. However, by increasing the amount of MLSS to 3000 mg L−1, the COD removal efficiency reached to 84.09% (from 176 to 28 mg L−1) and at the 5000 mg L−1 of MLSS, the COD removal efficiency was 91.52% (from 236 to 20 mg L−1). It can be concluded from this study, although, the UV/Iodide ARP was very effective in breaking down OFL molecules, but it is not cost-effective due to the high time and cost of mineralisation. Therefore, application of the biological reactors as a post-treatment method after UV/Iodide ARP, due to cost-effective, environmentally friendly and the ability to degrade the intermediates produced can be useful.

Removal of antibiotics from wastewaters by membrane technology: Limitations, successes, and future improvements.

Antibiotics and related pharmaceuticals are applied to enhance public health and life quality. A major environmental concern is wastewaters from pharmaceutical industries, which contain significant amounts of antibiotics. Pharmaceutical industries apply conventional processes (biological, filtration, coagulation, flocculation, and sedimentation) for wastewater treatment, but these approaches cannot remove antibiotics completely. Moreover, unmetabolized antibiotics released by humans and animals are dangerous for municipal and effluent wastewater. Besides, antibiotic resistance is another challenge in treatment of wastewater for superbugs. This comprehensive study summarizes different techniques for antibiotic removal with an emphasis on membrane technology in individual and hybrid systems such as chemical, physical, biological, and conditional-based strategies. A combination of membrane processes with advanced oxidation processes (AOPs), adsorption, and biological treatments can be the right solution for perfect removal. Furthermore, this review briefly compares different procedures for antibiotic removal, which can be helpful for further studies with their advantages and drawbacks.

Comparison of Swine Wastewater Treatment by Microalgae and Heterotrophic Nitrifiers: Focusing on Nitrogen Removal Mechanism Revealed by Microbiological Correlation Analysis

Swine wastewater (SW) poses a great threat to the environment due to its high-nutrient profiles if not properly managed. Advanced biological treatment method is an efficient method to treat SW by screening potent microalgae or bacterial strains. In this study, activated sludge, three locally isolated heterotrophic nitrification bacteria and one microalgal strain (Chlorella) were used as inoculums in treating a local SW. Their treatment efficiencies were compared, while the nitrogen removal mechanisms and microbiome profile were explored in detail. It was found that certain heterotrophic nitrification strains had a slight advantage in removing chemical oxygen demand and phosphorus from SW, with the highest removal efficiencies of 83.9% and 76.2%, respectively. The removal efficiencies of ammonia nitrogen and total nitrogen in wastewater by microalgae reached 80.9% and 66.0% respectively, which were far higher than all the heterotrophic nitrification strains. Biological assimilation was the main pathway of nitrogen conversion by microalgae and heterotrophic nitrifying bacteria; especially microalgae showed excellent biological assimilation performance. Correlation analysis showed that Comamonas was highly positively correlated with nitrogen assimilation, while Acidovorax was closely correlated with simultaneous nitrification and denitrification. This study gives a comparison of microalgae and heterotrophic nitrifying bacteria on the nitrogen transfer and transformation pathways.

In-Situ Sludge Reduction in Membrane-Controlled Anoxic-Oxic-Anoxic Bioreactor: Performance and Mechanism.

Conventional and advanced biological wastewater treatment systems generate excess sludge, which causes socio-economic and environmental issues. This study investigated the performance of membrane-controlled anoxic-oxic-anoxic (AOA) bioreactors for in-situ sludge reduction compared to the conventional anoxic-oxic-oxic membrane bioreactor (MBRcontrol). The membrane units in the AOA bioreactors were operated as anoxic reactors at lower sludge recirculation rates to achieve hydrolysis of extracellular polymeric substances (EPS) and extensive endogenous respiration. Compared to MBRcontrol, the AOA bioreactors operated with 90%, and 80% recirculation rates reduced the sludge growth up to 19% and 30%, respectively. Protein-like components were enriched in AOA bioreactors while fulvic-like components were dominant in MBRcontrol. The growth of Dechloromonas and Zoogloea genra was promoted in AOA bioreactors and thus sludge reduction was facilitated. Metagenomics analysis uncovered that AOA bioreactors exhibited higher proportions of key genes encoding enzymes involved in the glycolysis and denitrification processes, which contributed to the utilization of carbon sources and nitrogen consumption and thus sludge reduction.

Advanced Oxidation Pretreatment for Biological Treatment of Reclaimer Wastewater Containing High Concentration N-methyldiethanolamine

A wastewater treatment configuration consisting of advanced oxidation pretreatment and biological wastewater treatment process (BWTP) was investigated to treat a reclaimer wastewater generated in a steel-making industry, which contained high concentration MDEA (N-methyldiethanolamine) of up to 20,548 mg/L and other pollutants such as formate, phenol, and thiocyanate. The Fenton, ozone, and peroxone methods were tested as candidates, and the peroxone method was chosen because it could selectively decompose MDEA resulting in the final MDEA and chemical oxygen demand (COD) removal efficiencies of 92.87% and 27.16%, respectively. Through the respirometer tests using the sludge of the BWTP, it was identified that the microbial toxicity of the peroxone-pretreated wastewater was negligible and the short-term biochemical oxygen demand (BOD) to COD ratio, indicating that the biodegradability of wastewater significantly increased from 0.103 to 0.147 by the peroxone pretreatment. Analysis of the oxygen uptake rate profiles also revealed that the microbial degradation rate of the pollutants present in the reclaimer wastewater was in the order of phenol &gt; formate &gt; thiocyanate &gt; MDEA, which could be changed depending on the microbial community structure of the BWTP.

Endocrine disrupting chemicals (EDCs) in environmental matrices: Occurrence, fate, health impact, physio-chemical and bioremediation technology

Endocrine disrupting chemicals (EDCs) are an emerging category of toxicity that adversely impacts humans and the environment's well-being. Diseases like cancer, cardiovascular risk, behavioral disorders, autoimmune defects, and reproductive diseases are related to these endocrine disruptors. Because these chemicals exist in known sources such as pharmaceuticals and plasticizers, as well as non-point sources such as agricultural runoff and storm water infiltration, the interactive effects of EDCs are gaining attention. However, the efficiency of conventional treatment methods is not sufficient to fully remediate EDCs from aqueous environments as the occurrence of EDC bioremediation and biodegradation is detected in remediated drinking water. Incorporating modification into current remediation techniques has to overcome challenges such as high energy consumption and health risks resulting from conventional treatment. Hence, the use of advanced psychochemical and biological treatments such as carbon-based adsorption, membrane technology, nanostructured photocatalysts, microbial and enzyme technologies is crucial. Intensifying environmental and health concerns about these mixed contaminants are primarily due to the lack of laws about acute concentration limits of these EDCs in municipal wastewater, groundwater, surface water, and drinking water. This review article offers evidence of fragmentary available data for the source, fate, toxicity, ecological and human health impact, remediation techniques, and mechanisms during EDC removal, and supports the need for further data to address the risks associated with the presence of EDCs in the environment. The reviews also provide comprehensive data for biodegradation of EDCs by using microbes such as fungi, bacteria, yeast, filamentous fungi, and their extracellular enzymes.

Evaluation of occurrence, fate and removal of priority phthalate esters (PAEs) in wastewater and sewage sludge by advanced biological treatment, waste stabilization pond and constructed wetland

Phthalate Esters (PAEs), detected in high concentrations generally in treated wastewater discharged from wastewater treatment plants (WWTPs), are important pollutants that restrict the reuse of wastewater. Investigating the fate of these endocrine-disrupting chemicals in WWTPs is crucial in order to protect both receiving environments and ecosystems. For this purpose, di(2-ethylhexyl) phthalate (DEHP), di-n-octyl phthalate (DNOP) and benzyl butyl phthalate (BBP) in the group of PAEs were monitored in simultaneously both in wastewater and sludge lines of selected two nature-based WWTPs and one advanced biological WWTP.Although it was frequently stated that phthalates were significantly removed in WWTPs in many studies found in literature, negative removal efficiencies of selected phthalates in investigated WWTPs during the sampling period were observed generally in this study. One of the reasons for this concentration increase could be releasing of phthalates from microplastics in wastewater during the treatment process or the desorption of PAEs from treatment sludge. DNOP was the compound with the highest concentration increase at almost each treatment unit of the three WWTPs. On the other hand, total PAEs load was 1997 g d−1 in advanced biological WWTP and adsorption onto sludge of PAEs were determined as 90%. The side-stream total load returned from the decanter supernatant was 0.02% of the total PAEs load coming to advanced biological WWTP from the sewer system.As a result of detailed statistical analysis, the correlation between raw wastewater and primary clarifier (PC) effluent was determined as an increasing linear relation for DEHP and DNOP. On the other hand, moderate and strong correlations were observed both between septic tank and constructed wetland (CW) processes with raw wastewater. In the waste stabilization pond (WSP), while a significant correlation was not found between the sludge line data, homogeneous variance, strong and moderate correlations were obtained in the wastewater line data. However, while mean differences for all investigated PAEs were not significant (p > 0.05) in the wastewater line, mean differences of DEHP (p < 0.05) were significant in the sludge line according to ANOVA analysis.

Effect of extracellular polymeric compositions on in-situ sludge minimization performance of upgraded activated sludge treatment for industrial wastewater

The sludge yield minimization from advanced biological treatment for industrial wastewater could be considered a poorly explored area, therefore, seeks serious attention of the scientific community. Up to best of the knowledge, the extracellular polymeric substances (EPS) profile underlying an upgraded activated sludge treatment (as MANODOX system) for real tannery wastewater has not been addressed in a desired manner. This study covers the elucidation of EPS degradation mechanism and floc morphology underlying MANODOX system for the treatment of real tannery influent. For this purpose, a modified heat extraction method was followed for the estimation of EPS fractions like protein (PN), polysaccharides (PS) and humic contents from the sludge. For the present investigation, the variation in floc characteristics including PN/PS ratio, sludge hydrophobicity, sludge volume index, and facultative microbiota at corresponding change in hydrodynamic sludge retention time (SRT) of 08–40 days was emphasized. The strict maintenance of adapted operational strategies including favoring range of SRT (24 days) for MANODOX implementation succeeded an outstanding in-situ sludge yield minimization lowered up to 0.39 gMLSS/gTCOD that attributed to three times lowered accumulation of PN and PS, comparably lower PN/PS ratio, higher salinity of the mixed liquid, weakened cell-to-cell attachment compared with a parallel run identical aerobic treatment. Here, the reason for improved hydrophobicity and corresponding decline in floc aggregation was attributed to change in sludge PN/PS ratio, carbon to nitrogen ratio of feed influent. The observations confirmed that the sludge yield minimization from MANODOX like systems could be effectively controlled by maintaining aforementioned operational tactics.