Effluent Concentrations Research Articles

Preparation and optimization of sulfur ferrous inorganic carbon composite filler for autotrophic denitrification nitrogen and phosphorus removal

Sulfur autotrophic denitrification (SAD) occurs without organic carbon sources, offering advantages in removing nitrogen pollutants from water with low carbon to nitrogen ratio. However, ensuring nitrate–reducing sulfide–oxidizing bacteria ability to access the necessary sulfur and inorganic carbon sources is a challenge. Therefore, this study investigated the feasibility of utilizing a SAD composite filler to mitigate nitrogen and phosphorus pollutants concentrations in secondary effluent of wastewater treatment plants (WWTPs) and reduce eutrophication risk in the receiving water. The use of paraffin optimized composite filler with a satisfying 3.70 % break rate and wear rate without dramatically deteriorating contaminant removal performance. The process achieved 94.26 % total nitrogen (TN) and 90.91 % PO43--P removal rates in treating synthetic wastewater; and 2.72±1.92 and 0.29±0.06 mg/L of TN and PO43--P discharge in treating WWTPs secondary effluent, respectively. The results indicated that denitrification performance of the filler was primarily influenced by variations in NH4+-N resulting from SAD and dissimilatory nitrate reduction to ammonia caused by differences in filler composition and preparation factors. Based on the performance difference in SAD, Fex+ leached by H+ in the filler changed, affecting phosphorus removal performance. The change in mechanical properties of the filler was primarily dependent on the surface characteristics of the filler and the content/type of the binder. This study demonstrates the feasibility of using SAD for advanced nitrogen and phosphorus removal from wastewater and applying sulfur/siderite integrated composite filler as a pilot, thereby offering insights for the preparation of SAD fillers.

Enhanced nitrogen removal for low C/N wastewater via preventing futile carbon oxidation and augmenting anammox

Efficient carbon use is crucial for biological nitrogen removal. Traditional aerobic processes can waste carbon sources, exacerbating carbon deficiency. This study explores an anaerobic/oxic/anoxic system with sludge double recirculation to improve nitrogen removal in low C/N wastewater. This system integrated aerobic nitrification after the carbon intracellular storage, separating carbon and nitrogen by denitrifying glycogen-accumulating organisms (DGAOs) with endogenous partial denitrification and Anammox within the anoxic units. A significant efficiency of 91.02±7.01% chemical oxygen demand (COD) was converted into intracellular carbon in anaerobic units, significantly reducing carbon futile oxidation in the aerobic units by effectively separating COD from ammonia. Intracellular storage of carbon sources and microbial adaptation to carbon scarcity prevent futile oxidation of COD in the aerobic units even with short-term high dissolved oxygen (DO), thereby enhancing nitrogen removal under anoxic conditions with sufficient intracellular carbon source. The microbial analysis identified Candidatus Brocadia as the dominant anammox bacteria, in combination with the activity of DGAOs and other related microbial communities, accounting for 37.0% of the TN removal. Consequently, the system demonstrated remarkable nitrogen removal efficiencies, achieving 81.3±3.3% for total nitrogen (TN) and 98.5±0.9% for ammonia nitrogen while maintaining an effluent COD concentration of 17.2±9.1 mg/L, treating the low C/N of 4.18 in the influent wastewater. The findings in this study provide a sustainable and energy-saving technique for conventional WWTPs to meet strict discharge standards by avoiding futile oxidation of COD and encouraging anammox contributions.

Microplastic Contamination in Landfill Leachate and Surface Water: Assessment of Wastewater Treatment Efficiency at the Nonthaburi Waste Management Center, Thailand

Microplastics (MPs), plastic particles smaller than 5 mm, have emerged as a significant environmental concern, particularly as contaminants originating from landfills. Landfills can serve as a major source of MPs, potentially releasing them into surface water through leachate. This study aims to investigate the contamination of MPs in leachate and surface water, as well as to evaluate the efficiency of landfill wastewater treatment in removing these particles. The research was conducted at the Waste Management Center of the Nonthaburi Provincial Administrative Organization, Thailand, with samples collected in June 2023. Sampling included two leachate sources, influent and effluent from the treatment system and surface water. The abundance and characteristics of MPs in each sample were analyzed. Results indicated a significant presence of MPs in leachate, with an average concentration of 173.98 pieces/L, while concentrations in influent, effluent and surface water were 38.40 pieces/L, 10.80 pieces/L and 11.33 pieces/L, respectively. MPs in all samples were predominantly in the size range of 16-100 µm, corresponding to 71.28-93.75% of the total particles. Polypropylene was the dominant polymer in leachate (69.66%) and effluent (48.94%), whereas acrylate copolymer (96.53%) and polytetrafluoroethylene (44.12%) were the major types found in influent and surface water, respectively. The wastewater treatment system of the landfill demonstrated an overall removal efficiency of 71.88% for MPs in leachate. These findings highlight the extent of MP contamination in landfill environments and the importance of improving treatment processes to mitigate their release into surrounding ecosystems.

Measuring Microplastic Concentrations in Water by Electrical Impedance Spectroscopy

Plastics are vital for society, but their usage has grown exponentially and contributes to the growth of pollution worldwide. The World Health Organization, WHO, already reported that microplastics (MPs) are found everywhere, in waste and fresh water, and in the air and soil. Regarding water effluents, waste-water treatment plants only minimize the problem, trapping only larger size particles. In contrast, smaller ones remain in oxidation ponds or sewage sludges, or are even released to aquifers environment. Classic procedures for MPs detection are still quite laborious, and are usually conducted off-line, involving several steps and expensive equipment. Electrical Impedance Spectroscopy, EIS, is a technique that allows the analysis of a system’s electrical response, yielding helpful information about its domain-dependent on physical-chemical properties. Due to the superficial electronegativity of MPs’ particles, EIS may allow to attain the purpose of the present work: to provide a fast and reliable method to detect/estimate MPs’ concentration in water effluents. Among the most common microplastics are Polyethylene, PE, and Polyvinyl Chloride, PVC. Using the developed setup and experimental data collection methodology, the authors could differentiate between MPs’ suspensions containing the same concentration of the different evaluated MPs, PVC and PE, and assess PVC concentration variation, in the interval between 0.03 to 0.5 g (w/w), with an error, estimated based on the obtained impedance modulus, around or below 3% for the entire stimulus signal frequency range (from 100 Hz to 40 MHz) for the PVC particles.

Study on Operation Effect of Two-Stage MSL System for Rural Decentralized Sewage Treatment

To improve the removal efficiency of rural domestic sewage, a two-stage multi-soil-layer sewage treatment system with an “aeration section + non-aeration section” was designed, and its treatment performance was observed under different influent loads and aeration intensities. The experiment ran for a total of 150 days, and the results showed that the two-stage multi-soil-layer (MSL) system could effectively reduce the effluent concentration of sewage to meet discharge standards. Under the operating conditions of an influent hydraulic load of 1000 L·m−2·d−1 and an air–water ratio of 4:1, the final effluent average concentrations of COD, NH3-N, TN, and TP were 106.5 mg·L−1, 7.4 mg·L−1, 13.9 mg·L−1, 0.12 mg·L−1, and 18.6 mg·L−1, respectively, with average removal rates of 85.3%, 82%, 72.5%, 96%, and 85%. A longer hydraulic retention time and ideal anoxic conditions were ensured by designing a certain effluent height in the system. Adding aeration to the system allowed for a synchronous nitrification–denitrification reaction under reasonable influent loads, ultimately enabling the effluent to meet discharge standards.

Systematic evaluation of swale length, shape, and longitudinal slope with simulated highway runoff for better swale design.

Swales are a low-cost, conveyance and treatment system to manage roadway runoff, but available design guidance is limited. Eight grass swales were constructed in Raleigh, North Carolina, USA, to systematically evaluate the effects of design factors: length, shape, and longitudinal slope under two different storm sizes. Water from an onsite reservoir was used to generate synthetic runoff and simulate flow through the swales. Inflow volume, total suspended sediment (TSS), nitrogen, phosphorus, and four total metals (copper, lead, zinc, and cadmium) were tested with simulated levels representing highway runoff. Efficiency ratios were used to estimate the reductions in inflow volume, pollutant concentrations, and mass loads. Swale length, shape, longitudinal slope, and storm size significantly influenced runoff volume reduction. The longer (30m) trapezoidal swale constructed on the flatter (1%) longitudinal slope provided maximum reductions in sediment and heavy metal concentrations during small-medium storms. Larger storms had modestly reduced pollutant and volume mitigation. Effluent nutrient concentrations generally exceeded the influent exporting nitrogen and phosphorus from all swale configurations. Significantly better pollutant load reductions were provided by the longer swales for all pollutants, except dissolved phosphorus. Therefore, to optimize swale function, designers could maximize the swale length to the greatest extent practicable, particularly when swales receive inflow from end-of-pipe systems draining roadway surfaces. The trapezoidal cross-section was superior to the triangular cross-section for stormwater treatment. Proper vegetation establishment and maintaining optimal grass height are key to proper swale functioning.

Influence of rubber particle inputs on nitrogen removal efficiency of bioretention systems

ABSTRACT Bioretention systems effectively capture rubber particles and other microplastics in stormwater runoff. However, it is uncertain whether long-term particle accumulation affects pollutant removal efficacy. This study investigated the impact of various concentrations of ethylene-propylene-diene-monomer (EPDM) particles (0, 50, 100, and 400 mg/L) on bioretention system nitrogen removal performance. The input of EPDM during short-duration (2 h) rainfall favored the removal of nitrogen, and the total nitrogen effluent concentration of the bioretention system with EPDM was reduced by 0.59–1.52 mg/L compared with that of the system without EPDM. In addition, the input of EPDM reduced the negative effects of drought. During long-duration (24 h) rainfall, higher concentrations of EPDM led to lower nitrate–nitrogen concentrations in the effluent. The bioretention system with EPDM required less time for nitrate–nitrogen removal to reach 50% than that without EPDM input. Microbial community analysis showed that EPDM increased the relative total abundance of denitrifying bacteria (such as Dechloromonas, Zoogloea, Ramlibacter, and Aeromonas) by 7.25–10.26%, which improved the denitrification capacity of the system.

Analysis on pollutants removal and sludge characteristics of a novel two-phase anaerobic/aerobic/integrated deoxygenated and anoxic reactor associated with membrane process for treating pesticide wastewater

Most frequently used biological method was improved anaerobic/anoxic/aerobic (A/A/O) process for treating actual pesticide wastewater presently. However, the effluent results were far away from what the national standard expects due to pesticide wastewater characteristics of high COD concentration, high total nitrogen (TN) concentration and high toxicity. In this study, a novel two-phase anaerobic/aerobic/integrated deoxygenated and anoxic reactor associated with membrane process (P1) were regarded as excellent candidates for the treatment of pesticide wastewater, compared the removal efficiency of pollutants with improved A/A/O process (P2) under different hydraulic retention times (HRTs). Effluent ethylene thiourea (ETU) concentration was reduced effectively by 67.1 % in P1. The average cyanide (CN−) effluent concentration in P1 and P2 was 0.40 mg/L and 6.67 mg/L, respectively. During the entire HRT change period, P1 significantly increased the biological oxygen demand (BOD5) removal efficiency by 12.98 %. The average effluent COD concentration of P1 was 36.41 mg/L, while that of P2 was 984.42 mg/L. In addition, TN removal efficiency of P1 exhibited distinct superiority. When HRT was 72 h, the average TN effluent concentration of P1 and P2 was 12.67 mg/L and 67.66 mg/L. The sludge performance indicators have been determined and results showed that the sludge viscosity of the membrane reactor in P1 had merely 32.6 % higher than that of the secondary sedimentation tank in P2, and the average vertical displacement of sludge settleability in P1 was 23.0 % slight lower than that of P2. The overall sludge performance proved that higher sludge concentration was allowed in P1. Moreover, experiment improved nitrite reductase (NIR) and nitrate reductase (NAR) in P1 were less susceptible to be suppressed by ETU and CN− increase compared with P2. Finally, the positive correlation relationship of sludge settleability with ETU and CN− has been identified successfully in P1.

Effect of Palm Oil Mill Effluent (Pome) Concentration and Soil Type on the Growth of Oil Palm (Elaeis guinensis Jacq) in Pre-Nursery

The place of research was carried out at Educational and Research Garden of the STIPER Agricultural Institute which is located in Maguwoharjo Village, Depok District, Sleman Regency, Yogyakarta, Indonesia. The research location is located 118 meters above sea level. This research was conducted between March to June 2024. Two components make up the factorial experiment used in the Complete Randomized Design (CRD). The soil type had three levels: A1 = latosol soil, A2 = regusol soil, and A3 = grumusol soil, was the first factor. Palm Oil Mill Effluent (POME) concentration was the second factor. It was consisted into four levels: X1 was the control (NPK fertilizer), X2 was 150 ml per polybag, X3 was 300 ml per polybag, and X4 was 450 ml per polybag. So there were 12 treatment combinations (3 x 4 = 12) with 4 repetitions, so all the experiment 48 plants. Analysis of variance (ANOVA) was applied at the significant level of 5% to check the observation data. Duncan's Multiple Range Test (DMRT) was then used at a noticeable 5% level if there was significant difference. The weight parameters of fresh roots and the amount of chlorophyll in the leaves are influenced by the interaction of the soil and POME concentration. The composition, regusol soil and POME 450 ml/polybag provide an optimal combination of treatments. The type of soil has an impact on the weight of fresh and dry crowns, the number of leaves, the chlorophyll content in the leaves, the volume of roots, and the height of the plant. The best type of soil is regusol soil. Plant height, root volume, fresh and dry crown weight, and leaf chlorophyll content are all affected by POME concentration. The concentration of POME 450 ml/polybag showed the best results.

Measurement of Acrylamido Tertiary Butyl Sulfonate Polymer Retention on Limestone by Three Methods Under Varying Temperature and Oil Presence

Summary Polymer retention poses a significant challenge in polymer flooding applications, emphasizing the importance of accurately determining retention levels for successful project design. In carbonate reservoirs of the Middle East, where temperatures exceed 90°C, conducting adsorption tests under similar temperature conditions becomes crucial for the precise determination of adsorption values. The choice of analytical method potentially impacts the accuracy of retention measurements from effluent analysis. This study investigates the effect of temperature on the performance of a polymer, specifically its rheological behavior and retention. Rheological and polymer flooding experiments were carried out using an acrylamido tertiary butyl sulfonate (ATBS)-based polymer in formation water (167,114 ppm) at different temperatures (25°C, 60°C, and 90°C) with required oxygen control measures. Dynamic polymer retention was conducted in both the absence of oil (single-phase tests) and the presence of oil (two-phase tests). In addition, different analytical techniques were evaluated, including viscosity measurements, ultraviolet (UV)-visible spectroscopy, and total organic carbon-total nitrogen (TOC-TN) analysis, to determine the most accurate method for measuring the polymer concentration with the least associated uncertainty. Furthermore, the study investigates the effects of these uncertainties on the final dynamic polymer retention values by applying the propagation of error theory. The effluent polymer concentration was determined using viscosity correlation, UV spectrometry, and TOC-TN analysis, all of which were reliable methods with coefficient of determination (R2) values of ~0.99. The study analyzed the effects of flow through porous media and backpressure regulator on polymer degradation. The results showed that the degradation rates were around 2% for flow through porous media and 16% for mechanical degradation due to the backpressure regulator for all temperature conditions. For the effluent sample, the concentration of polymer was lower when using the viscosity method due to polymer degradation. However, the TOC-TN and UV methods were unaffected as they measured the TN and absorbance at a specific wavelength, respectively. Therefore, all viscosity results were corrected for polymer degradation effects in all tests. During the two-phase coreflooding experiment conducted at 25°C, the accuracy of the UV spectrometry and viscosity measurements was affected by the presence of oil, rendering these methods unsuitable. However, the TOC-TN measurements were able to determine effluent polymer concentration and, subsequently, the retention value. Moreover, the use of glycerin preflush to inhibit oil production during polymer injection in the two-phase studies showed that all three methods were appropriate. The error range was obtained using the propagation of error theory for all the methods. Accordingly, it was noted that the temperature did not affect the dynamic retention values in both single-phase and two-phase conditions. The findings of this study highlight that when adequate oxygen control measures are implemented, the temperature does not exhibit a statistically significant impact on the retention of the ATBS-based polymer under investigation. Furthermore, TOC-TN has been identified as the optimal analytical method due to its minimal uncertainties and ease of measuring polymer concentration under varying experimental conditions.

Biofilm characterization and dynamic simulation of advanced rope media reactor for the treatment of primary effluent.

Biofilm modeling is inherently complex, often requiring multiple assumptions and simplifications. In biofilm modeling, default or literature-based values in biofilm systems are usually used to estimate biofilm parameters, including boundary layer, biofilm density, thickness, attachment, and detachment rates. This study aimed to characterize and model the biofilm of a specific rope-type fixed media system, removing carbon and total inorganic nitrogen, coupled with sensitivity analysis. Among the five model parameters, the sensitivity analysis of this study showed that boundary layer thickness is the most influential parameter for predicting effluent ammonia and nitrate concentrations, and biofilm density is most sensitive with respect to effluent chemical oxygen demand (COD). The least sensitive parameter is the detachment rate. Based on the calculated mean absolute error (MAE) and root mean squared error (RMSE), the calibrated BioCord fixed-film reactor (BFFR) model accurately predicted effluent ammonium and dissolved oxygen (DO) in the continuously aerated bench-scale reactor (R1) and failed to predict well in the intermittently aerated bench-scale reactor (R2). RMSE values calculated for NH3-N and DO in R1 are 0.95 and 0.53 mg/L, respectively. In the BioCord pilot plant's case, ammonium-N predicted by the model fit the measured values well, while it overpredicted DO concentrations. PRACTITIONER POINTS: Fixed biofilm BioCord reactors were studied for primary effluent treatment. A methodology was developed to characterize biofilms. Boundary layer thickness is the most influential parameter for predicting effluent ammonia and nitrate concentrations. Biofilm density is the most sensitive parameter with respect to effluent COD. The calibrated BFFR model can predict effluent ammonium, nitrite, and nitrate-nitrogen.

Interpretable causal machine learning optimization tool for improving efficiency of internal carbon source-biological denitrification

Interpretable causal machine learning (ICML) was used to predict the performance of denitrification and clarify the relationships between influencing factors and denitrification. Multiple models were examined, and XG-Boost model provided the best prediction (R2 = 0.8743). Based on the ICML framework, hydraulic retention time (HRT), mixture chemical oxygen demand/total nitrogen (COD/TN = C/N), mixture COD concentration, and pretreatment technology were identified as important features affecting the denitrification performance. Further, tapping point and partial dependence analyses provided the range of key factors that precisely regulate denitrification. In the application analysis, HRT (6–10.5 h), mixture C/N (6–12), and mixture COD concentration (300–600 mg L−1) were the appropriate operating ranges, achieving TN removal of approximately 73 %–77 %. The effluent TN and COD concentrations met the discharge standards for wastewater in China (class 1A) and EU. These findings provide support for regulating excess sludge as internal carbon source to promote denitrification.

Robust PD/A biofilms sustain advanced real municipal wastewater treatment: Reinforcement of interspecific communication and electron transfer

In this study, a robust partial denitrification/anammox (PD/A) biofilm system was efficiently established within merely 83 days using solely conventional activated sludge as the inoculum, employing a multivariate regulation strategy involving the addition of biofillers, optimization of municipal wastewater feeding ratios, prolongation of hydraulic retention time, and introduction of hydrazine. The performance variability of PD/A system within a long-term, intricate mainstream substrate environment was further investigated by incrementally elevating municipal wastewater proportion (50 % → 75 % → 100 %). The results demonstrated that PD/A system ultimately achieved an impressive total nitrogen removal efficiency of 93.6 % and an effluent total nitrogen concentration of 8.6 mg/L, accompanied by anammox contributing over 85 % to nitrogen removal. The biofilm’s layered spatial structure nurtured Candidatus Brocadia, enabling it to reach an abundance of 2.5 % under high real municipal wastewater loading. Metabolic function analyses revealed that biofilm enhanced the abundance of genes associated with interspecies electron transfer and quorum sensing communication in PD/A consortia after prolonged exposure to municipal wastewater. These findings underscore the significances of interspecific interactions, bacterial communications, and synergistic metabolic traits within PD/A biofilm systems in the stabilization of real municipal wastewater treatment.

Filtro empacado con residuos de lodos de Al para la eliminación de fósforo como sistema de pulimento en una planta de tratamiento de aguas residuales

Recently, using residual aluminum sludge (Al-sludge) from drinking water treatment plants for phosphorus removal has been assessed and it has shown to be highly efficient. However, most of the studies have been conducted using synthetic water. Only a few works have applied this method to real wastewater (WW), and none of them have been tested in continuous mode, as a polishing step, in a pilot-scale, decentralized wastewater treatment plant (WWTP). This paper aimed to evaluate the performance of an immersed filter packed with a bed of residual Al-sludge as a polishing system for Phosphorous removal, in a pilot-scale, decentralized WWTP. The study determined at laboratory-scale the capacity for phosphorus removal through batch and continuous tests using both synthetic and real wastewater and evaluated the effect of retention time. Based on the results, an Al-sludge immersed filter (Al-sludge Filter) at pilot-scale was constructed, implemented, and evaluated as a polishing step for the effluent of a decentralized-WWTP. The results showed that during continuous testing with real WW, the phosphorus removal capacity was 2.55 mg P-PO43-∙g-1 per gram of Al sludge using a retention time of 120 min. The Al-sludge filter as a polishing system presented an average removal efficiency of 94 ± 8 % and an effluent concentration of under 0.50 mg P-PO43-∙l-1 during the first 20 operational days. For the next 17 days, the system removed 85 ± 9 % on average, showing an effluent concentration of under 1.0 mg P-PO43-∙l-1. From operational day 32 onwards, the removal efficiency was 63.6 ± 10.7 %, with an average effluent concentration of 2.20 ± 0.39 mg P-PO43-∙l-1.

Evaluation of Effluent Quality Trends Before and After Filtration Through the Composite Filter from Shirere Wastewater Treatment Plant to River Isiukhu in Kakamega County, Kenya

The current stabilization ponds as wastewater treatment practices in urban areas have proven insufficient with continued discharge of untreated wastes into water bodies. Their challenge comes from inappropriate system selection and maintenance, improper design, construction mistakes, physical damage and hydraulic overload. Appropriate infrastructural technologies for waste removal that can be adopted in the drainage channels of effluents into water bodies are scarce. This study incorporates a reactor based composite filter of pumice and sand as an innovative approach for removing residual waste in effluents discharged from Shirere Wastewater Treatment Plant into River Isiukhu, Kakamega Municipality. The objective of the study was to evaluate the trend of effluent quality from Shirere wastewater treatment plant upto river Isiukhu before and after installation of composite granular filter. Effluents, drinking water from Shirere WWTP, Shikoye stream, River Isiukhu and protected spring along Shikoye stream, were collected using presterilized water sampling containers for microbial quality analysis at MMUST and KACWASCO laboratories. The measurements were carried out using UV-VIS spectrophotometer at 752 nanometer wavelengths. Research design was experimental. The average reduction of COD in the mid-season of June to August was 42.2 ±4.6%, being the highest. Concomitantly, the BOD removal by the filter in the season of June to August was19.6±7% and 15.6 ±3.5% for September to November. The average rate of TSS removal in June to August was 19.3±4.5% followed by 16.6±3.8% in September to November and 11.6±7% in March to May. The average rate of Nitrate removal in June to August was 41.8±7.6% followed by 30.0±2.2% for March to May and 25±8.6% for September to November. Phosphates had an average rate of removal in June to August at 31.9±2.7% followed by 20.6±4.8% for September to November and 20.0 ±4.3% for March to May. Specifically, for the first season of March – May 2021 at 200 mm filtration depth were carried out at effluent flow rate of 0.0032 and volume, 0.234 Concentrations of most parameters were above NEMA standards, like COD was 322mg/l yet maximum should be 100 mg/l. Therefore, it was concluded that silica pumice composite filter performance was achieved by big variations in the concentrations of COD, BOD, TSS, Phosphates and Nitrates at Shirere WWTP after filtration which was attributed to effective removing capacity. The effluent concentrations from sampling sites S1-S3 and S5-S7 were found to be above the NEEMA standards implying the high risk of using Isiukhu water and catchment area. Thus, this study recommended that, the composite filter reduced concentrations of all the parameters (COD, BOD, TSS, PO3, NO3) significantly from Shirere WWTP along Shikoye stream up to the confluence of river Isiukhu. Most of the parameters after filtration were ranging within the required standards of NEMA. The requisite measure of adopting new technology of composite filtration should be sustained.

Experimental study on the treatment of high COD metal degreasing cleaning wastewater by coagulation and two-stage Fenton oxidation

ABSTRACT In this study, based on the water quality characteristics of metal degreasing cleaning wastewater, wastewater treatment by coagulation combined with two-stage Fenton oxidation was proposed. The results showed that when the dosage of polyaluminium chloride (PAC) was 5 g/L and the dosage of cationic polyacrylamide (CPAM) was 8 mg/L, with an initial pH of 8, rapid stirring at 350 rpm for 3 min followed by slow stirring at 200 rpm for 15 min, the optimal removal rate of chemical oxygen demand (COD) in metal degreasing cleaning wastewater reached 74.08%. Primary Fenton oxidation is mainly aimed at decomposing macromolecular long-chain pollutants and removing some pollutants. The highest COD removal rate was achieved at 95.07% when the dosage of H2O2 was 4 mol/L, the dosage of FeSO4 was 40 g/L, the oxidation lasted for 60 min, the initial pH was 2, the effluent pH was 8, and the settling time was 90 min. The two-stage Fenton oxidation process provided further advanced treatment. With a reagent ratio of 1:0.5, the effluent COD concentration was reduced to 457 mg/L, meeting the third-class standard of the ‘Integrated Wastewater Discharge Standard’ (GB 8978 − 1996).

Behaviour, biochemical and histological responses of the freshwater mussels Unio ravoisieri exposed to wastewater from Wadi Guenniche (Northeastern Tunisia)

ABSTRACT Wastewater effluents increase contaminant levels in the aquatic environment, leading to various disruptive effects. In this study, responses of Unio ravoisieri transplanted into wastewater from Wadi Guenniche were monitored using filtration rate, oxidative stress, lipo-peroxidation, neurotoxicity and histopathological markers. The filtration rate was significantly increased by exposure to diluted wastewater, rising from 35.13 mg indiv−1 h−1 in the control to 63.49 mg indiv−1 h−1 in the mussels after 96 h of exposure. In contrast, this exposure significantly reduces catalase, glutathione-S-transferase and acetylcholinesterase activities in both organs. This decrease is dependent on the effluent concentration and time exposure. The malondihaldehyde content showed an increasing profile in both organs. It is only in the gills that this increase is significant for mussels transplanted in situ for 48 h. Contamination by wastewater causes histopathological changes in both organs, marked by infiltration, vacuolisation, secretion of lipofuscins and cell necrosis. The intensity of these lesions depends on the duration of exposure and the degree of pollution. The mean incidence of lesions increases depending on effluent concentration and exposure time in both organs. Our study contributes to the database on behavioural, biochemical and histopathological effects in mussels following the discharge of wastewater effluent into a freshwater ecosystem.

Investigation of Nitrogen Removal in Flue Gas Desulfurization and Denitrification Wastewater Utilizing Halophilic Activated Sludge.

In the process of flue gas desulfurization and denitrification, the generation of high-sulfate wastewater containing nitrogen is a significant challenge for biological wastewater treatment. In this study, halophilic activated sludge was inoculated in a Sequencing Batch Reactor to remove nitrogen from wastewater with a high sulfate concentration (60 g/L). With the influent concentration of 180 mg/L, the removal rate of total nitrogen was more than 96.7%. The effluent ammonium nitrogen concentration was lower than 1.94 mg/L, and the effluent nitrate nitrogen and nitrite nitrogen concentrations were even lower than 0.77 mg/L. The salt tolerance of activated sludge is mainly related to the increase in the content of ectoine in microbial cells. The Specific Nitrite Oxidation Rate is quite low, while the Specific Nitrite Reduction Rate and Specific Nitrate Reduction Rate are relatively strong. In the system, there are various nitrogen metabolic processes, including aerobic nitrification, anaerobic denitrification, and simultaneous nitrification-denitrification processes. By analyzing the nitrogen metabolic mechanisms and microbial community structure of the reaction system, dominate bacteria can be identified, such as Azoarcus, Thauera, and Halomonas, which have significant nitrogen removal capabilities.

Palygorskite-mediated simultaneous nutrient removal and antibiotic degradation from aquaculture wastewater in lab-scale constructed wetlands

In this study, palygorskite was employed as a substrate in laboratory-scale constructed wetlands (CWs) over a period of 180 days to investigate the removal efficiency of pollutants from mariculture wastewater under high loads of enrofloxacin (ENR) stress. The results indicated that the incorporation of palygorskite into CWs resulted in average effluent concentrations of total phosphorus (TP), total nitrogen (TN), chemical oxygen demand (COD), and ENR reaching 0.07 ± 0.00 mg/L, 1.07 ± 0.06 mg/L, 11.57 ± 1.04 mg/L, and 0.047 ± 0.002 mg/L, respectively. The removal efficiencies reached 96.45 ± 0.04 %, 94.62 ± 0.27 %, 88.61 ± 1.22 %, and 91.14 ± 5.00 % respectively, with phosphorus removal significantly surpassing that reported for similar CWs. This superior performance was mainly attributed to the strong binding mechanisms between phosphorus and the metal oxides and hydroxides leached from the palygorskite. The palygorskite stimulated the secretion of extracellular polymeric substances (EPS), accelerated biofilm establishment, and enhanced the relative abundance of key functional bacteria associated with carbon, nitrogen, and antibiotic removal, thus achieving rapid denitrification and efficient organic matter removal. Monitoring of metals (Ca, Fe, Mn, and Cu) in the CWs effluent suggested that their presence was insufficient to affect cytoplasmic enzyme activity or cause oxidative stress damage to plants. In conclusion, palygorskite serves as an environmentally friendly, high-nutrient removal alternative, apt as a substrate for CWs.

Microplastics and per- and polyfluoroalkyl substances (PFAS) in landfill-wastewater treatment systems: A field study

Landfills and wastewater treatment plants (WWTP) are point sources for many emerging contaminants, including microplastics and per- and polyfluoroalkyl substances (PFAS). Previous studies have estimated the abundance and transport of microplastics and PFAS separately in landfills and WWTPs. In addition, previous studies typically report concentrations of microplastics as particle count/L or count/g sediment, which do not provide the information needed to calculate mass balances. We measured microplastics and PFAS in four landfill-WWTP systems in Illinois, USA, and quantified mass of both contaminants in landfill leachate, WWTP influent, effluent, and biosolids. Microplastic concentrations in WWTP influent were similar in magnitude to landfill leachates, in the order of 102 μg plastic/L (parts-per-billion). In contrast, PFAS concentrations were higher in leachates (parts-per-billion range) than WWTP influent (parts-per-trillion range). After treatment, both contaminants had lower concentrations in WWTP effluent, although were abundant in biosolids. We concluded that WWTPs reduce PFAS and microplastics, lowering concentrations in the effluent that is discharged to nearby surface waters. However, partitioning of both contaminants to biosolids may reintroduce them as pollutants when biosolids are landfilled or used as fertilizer.