Stabilization Ponds Research Articles

Waste stabilization pond modelling using extreme gradient boosting machines

ABSTRACT The integrated solar and hydraulic jump-enhanced waste stabilization pond (ISHJEWSP) has been proposed as a solution to enhance performance of the conventional WSP. Despite the better performance of the ISHJEWSP, there is seemingly no previous study that has deployed machine learning (ML) methods in modelling the ISHJEWSP. This study is aimed at determining the relationships between the ISHJEWSP effluent parameters as well as comparing the performance of extra trees (ET), random forest (RF), decision tree (DT), light gradient boosting machine (LightGBM), gradient boosting (GB), and extreme gradient boosting (XGBoost) methods in predicting the effluent biochemical oxygen demand (BOD5) in the ISHJEWSP. The feature importance technique indicated that the most important were pH, temperature, solar radiation, dissolved oxygen (DO), and total suspended solids. These selected features yielded strong correlations with the dependent variable except DO, which had a moderate correlation. With respect to coefficient of determination and root mean square error (RMSE), the XGBoost performed better than the other models [coefficient of determination (R2) = 0.807, mean absolute error (MAE) = 4.3453, RMSE = 6.2934, root mean squared logarithmic error (RMSLE) = 0.1096]. Gradient boosting, XGBoost, and RF correspondingly yielded the least MAE, RMSE, and RMSLE of 3.9044, 6.2934, and 0.1059, respectively. The study demonstrates effectiveness of ML in predicting the effluent BOD5 in the ISHJEWSP.

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.

Longitudinal wastewater-based surveillance of SARS-CoV-2 during 2023 in Ethiopia.

Although wastewater-based epidemiology (WBE) successfully functioned as a tool for monitoring the coronavirus disease 2019 (COVID-19) pandemic globally, relatively little is known about its utility in low-income countries. This study aimed to quantify severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA in wastewater, estimate the number of infected individuals in the catchment areas, and correlate the results with the clinically reported COVID-19 cases in Addis Ababa, Ethiopia. A total of 323 influent and 33 effluent wastewater samples were collected from three Wastewater Treatment Plants (WWTPs) using a 24-h composite Moore swab sampling method from February to November 2023. The virus was captured using Ceres Nanotrap® Enhancement Reagent 2 and Nanotrap® Microbiome A Particles, and then nucleic acids were extracted using the Qiagen QIAamp Viral RNA Mini Kit. The ThermoFisher TaqPath™ COVID-19 kit was applied to perform real-time reverse transcriptase polymerase chain reaction (qRT-PCR) to quantify the SARS-CoV-2 RNA. Wastewater viral concentrations were normalized using flow rate and number of people served. In the sampling period, spearman correlation was used to compare the SARS-CoV-2 target gene concentration to the reported COVID-19 cases. The numbers of infected individuals under each treatment plant were calculated considering the target genes' concentration, the flow rate of treatment plants, a gram of feces per person-day, and RNA copies per gram of feces. SARS-CoV-2 was detected in 94% of untreated wastewater samples. All effluent wastewater samples (n = 22) from the upflow anaerobic sludge blanket (UASB) reactor and membrane bioreactor (MBR) technology were SARS-COV-2 RNA negative. In contrast, two out of 11 effluents from Waste Stabilization Pond were found positive. Positive correlations were observed between the weekly average SARS-CoV-2 concentration and the cumulative weekly reported COVID-19 cases in Addis Ababa. The estimated number of infected people in the Kality Treatment catchment area was 330 times the number of COVID-19 cases reported during the study period in Addis Ababa. This study revealed that SARS-CoV-2 was circulating in the community and confirmed previous reports of more asymptomatic COVID-19 cases in Ethiopia. Additionally, this study provides further evidence of the importance of wastewater-based surveillance in general to monitor infectious diseases in low-income settings. Wastewater-based surveillance of SARS-CoV-2 can be a useful method for tracking the increment of COVID-19 cases before it spreads widely throughout the community.

Application of Decentralized Wastewater Treatment Technology in Rural Domestic Wastewater Treatment

The management of domestic wastewater in rural areas has always been challenging due to characteristics such as the wide distribution and dispersion of rural households. There are numerous domestic sewage discharge methods used in rural areas, and it is difficult to treat the sewage. To address this problem, decentralized wastewater treatment systems (DWTSs) have been installed around the globe to reuse and recycle wastewater for non-potable uses such as firefighting, toilet flushing, and landscape irrigation. This study compares the currently implemented treatment processes by investigating them from the point of view of their performance and their advantages and disadvantages to provide new ideas for the development of rural wastewater treatment technologies. According to conventional treatment technologies including activated sludge (OD, A/O, A/A/O, SBR), biofilm (biofilter, MBBR, biological contact oxidation, biofluidized bed) and biogas digesters, natural biological treatment technologies including artificial wetlands (surface flow, vertical flow, horizontal submerged flow artificial wetlands), soil percolation systems (slow, fast, subsurface percolation and surface diffusion) and stabilization pond technology and combined treatment technologies are categorized and further described.

Trends of N2O production during decentralized wastewater treatment: a critical review

Nitrous oxide (N2O) emissions have become a significant concern due to their potential high contribution to the carbon footprint of wastewater treatment plants. While their production pathways in centralized systems have been already deeply investigated, an analysis of N2O production trends from decentralized wastewater treatment plants, with a detailed description of the operating conditions affecting N2O generation in each technology, is missing. In this work, research on N2O emission from several decentralized technologies, including septic tanks and leach fields, soil infiltration systems, waste stabilization ponds, onsite activated sludge systems, Johkasou systems, onsite advanced technologies and constructed wetlands is reviewed. N2O emissions were found to depend on operating parameters, among which aeration regime, light exposure, influent carbon-to-nitrogen ratio, environmental temperature, nitrite concentration, plant species, and pH. It was not always possible to clearly understand the influence of a specific parameter on N2O emissions, given the complexity of the producing pathways, the temporal and spatial N2O variability, and the limited data. Research gaps, such as the lack of monitoring nitrification and denitrification intermediates, and the lack of long-term N2O monitoring campaigns, have also been identified. Considering the widespread diffusion of decentralized wastewater technologies and their need to meet more stringent requirements on sanitation, it will be more and more important in the future to understand their specific contribution to wastewater treatment carbon footprint. Standardized monitoring techniques, established estimation methods for emission factors, and a wider application of mathematical models could help in achieving a greater understanding of the complex N2O generation pathways.

Evaluation of physical, chemical, and microbiological characteristics of waste stabilization ponds, Giza, Egypt

Wastewater treatment plants (WWTPs) contain a diverse array of microbes, underscoring the need for regular monitoring to ensure treatment efficacy and protect health. However, detailed studies on waste stabilization ponds (WSPs) are scarce. This study evaluates a full-scale WSP, located in Giza Governorate, Egypt, including anaerobic, facultative, and maturation ponds, examining an array of parameters such as enteric viruses, microeukaryotes (protozoa and algae), bacterial indicators, bacterial pathogens, and physicochemical characteristics. Utilizing multivariate statistical models, we identified significant distinctions in physicochemical parameters and microbial communities, primarily driven by treatment stages rather than temporal variations. In addition, seven viruses (human rotavirus, adenovirus, norovirus, astrovirus, hepatitis A virus, polyomavirus, and papillomavirus) were detected during the different stages (inlet, anaerobic, facultative, and outlet) of the WSP, except norovirus and papillomavirus were absent in the outlet stage. The viral log means reductions ranged from 1.24 to 5.94, depending on the stage and virus type. The removal efficiency of bacterial pathogens was more than 99%. High throughput 18S rRNA gene amplicon sequencing indicated the dominance of animal parasitic Apicomplexa species and Vermamoeba spp. in the WSP. Network analysis indicated significant roles for Ciliophora in virus reduction. Notably, the maturation pond's outlet was dominated by Spirulina maxima, whose mat-forming tendencies may inhibit pathogen removal by providing protective shelters. Although the WSP effectively reduced pathogen levels, the high initial loads resulted in considerable concentrations in the final effluent, posing ongoing public health concerns. This study highlights the imperative of including pathogen standards in national regulations for wastewater reuse.

PSXII-8 Environmental cost effects of different manure treatment methods on dairy farms

Abstract The issue of manure disposal in dairy farms has long been a significant challenge afflicting the dairy farming industry, as manure poses various detrimental effects such as greenhouse gas emissions and land pollution. This remains an urgent concern for the industry to address. The traditional tank fermentation oxidation pond form of manure treatment and the new biogas power generation mode of manure treatment are currently widely employed in dairy farming enterprises. The evaluation and analysis of the environmental cost of new treatment modes should be conducted using scientific methods to determine which approach is more environmentally friendly. We selected two dairy farms with roughly the same number of dairy cows and the same management level, and the feed formula of the two dairy farms was basically consistent with the herd structure. Among them, the traditional tank fermentation manure treatment pasture, and the biogas power generation pasture. The Life Cycle Assessment (LCA) method of SimaPro software was used, and the software version was 9.0.0.48. In the life cycle assessment, we take into account the depletion of fossil energy, cement, metals, chemical products, electricity, heat, and mechanical pumps during the process of manure treatment. After accounting, the following conclusions are developed. During the whole life cycle of dairy farming, greenhouse gas emissions mainly fall into three types: methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O). CH4 accounts for 64% of the total emissions, which is mainly produced in the process of animal feeding, and a small part comes from manure treatment. CO2 accounts for 34% of the total emissions from the production of feed raw materials. The smallest proportion of transport and fossil energy consumption is N2O, which is mainly produced by manure treatment processes and accounts for 2% of total emissions. The environmental cost of the traditional tank fermentation oxidation pond is 17.6% greater than that of the new type of biogas power generation.

Global modeling of photochemical reactions in lake water: A comparison between triplet sensitization and direct photolysis

The equivalent monochromatic wavelength (EMW) approximation allowed us to predict the photochemical lifetimes of the lipid regulator metabolite clofibric acid (CLO, triplet sensitization) and of the non-steroidal anti-inflammatory drug diclofenac (DIC, direct photolysis ​+ ​triplet sensitization) in lakes worldwide. To do so, we used large lake databases that collect photochemically significant parameters such as water depth and dissolved organic carbon, which allow for a preliminary assessment of some photoreactions. Extension to other photoreactions is currently prevented by the lack of important parameters such as water absorption spectrum, suspended solids, nitrate, nitrite, pH, and inorganic carbon on a global scale. It appears that triplet-sensitized CLO photodegradation would be strongly affected by the dissolved organic carbon values of the lake water and, for this reason, it would be fastest in Nordic environments. By contrast, direct photolysis (DIC) would be highly affected by sunlight irradiance and would proceed at the highest rates in the tropical belt. Interestingly, the predicted lifetimes of CLO and DIC are shorter than the residence time of water in the majority of global lake basins, which suggests a high potential for photoreactions to attenuate the two contaminants on a global scale. Photodegradation of DIC and CLO would also be important in waste stabilization ponds, except for elevated latitudes during winter, which makes these basins potentially cost-effective systems for the partial removal of these emerging contaminants from wastewater.

Sewage Treatment by Kolkata’s Natural Wetland System

The metropolis of Kolkata stands uniquely positioned to implement a natural sewage treatment paradigm through the utilization of waste stabilization ponds, specifically within the East Kolkata Wetlands (EKW). These shallow oxidation ponds harness solar irradiation and algae bacteria symbiotic processes to effectively treat incoming sewage. Concurrently, nutrient-rich effluents are assimilated through fish production, converting available nutrients into protein—a hallmark of nature-based treatment. A portion of raw sewage is used to cultivate a chunk of vegetables before treatment in fish ponds, and the reclaimed water after treatment is used for vegetable and paddy cultivation downstream. This investigation explains the delineation of a sewage flow system to EKW, a Ramsar-designated site. Substantively, it offers quantitative insights into the sewage volumes and quality undergoing treatment. The sewage flow is higher in the winter months (909.07 MLD) compared to the summer months (709.34 MLD). In general, the sewage from the Kolkata city flowing to the EKW is moderately polluted. Extensive scrutiny of sewage from pond inlets and outlets serves as a quantitative metric for evaluating treatment efficacy. EKW efficiently treats the sewage, demonstrating 59.1% Biological Oxygen Demand (BOD) removal and a 99.28% reduction in fecal coliform. The natural treatment system excels in removing ammoniacal nitrogen (80.38%) and phosphate (90%). The treated water’s quality along the EKW boundary, culminating at the Kulti Gong River discharge point, was systematically assessed. Analytical findings indicate that all measured concentrations in the treated water adhere to prescribed inland surface water discharge standards prescribed by the Central Pollution Control Board, India, barring a marginal elevation in BOD during winter. Evidently, the EKW system adeptly manages substantial sewage volumes, fostering efficient treatment while concurrently facilitating resource recovery through fish production, yielding economic dividends. Despite its substantial land footprint, preserving this inherently sustainable wastewater management paradigm is imperative.

Heavy Metal Tolerance of some Filamentous Fungi from Waste Water of Oxidation Ponds in Sadat City

Heavy Metal Tolerance of some Filamentous Fungi from Waste Water of Oxidation Ponds in Sadat City

Occurrence, distribution, and fate evaluation of endocrine disrupting compounds in three wastewater treatment plants with different treatment technologies in Türkiye

Nowadays, two of the endocrine disrupting compounds (EDCs) in the group of alkylphenols (APs), nonylphenol (4-NP) and octylphenol (4-t-OP), have attracted great scientific and regulatory attention mainly due to concerns about their aquatic toxicity and endocrine disrupting activity. This paper investigated the occurrence, distribution behavior, fate, and removal of 4-NP and 4-t-OP in liquid and solid phases of three full-scale wastewater treatment plants (WWTPs) with different treatment technologies comparatively. In this context, (i) advanced biological WWTP, (ii) wastewater stabilization pond (WSP), and (iii) constructed wetland (CW) were utilized. In all three investigated WWTPs, the concentrations of 4-NP (219.9–19,354.4 ng/L) in raw wastewater were higher than those of 4-t-OP (13.9–2822.4 ng/L). Within the scope of annual average removal efficiencies, 4-NP was treated highly in advanced biological WWTP (93.5 %), while it was almost not treated in WSP (3.1 %) and treated with negative removal (<0 %) in CW. While 4-t-OP was treated at a similar removal rate (93.5 %) to 4-NP in advanced biological WWTP, it was treated moderately in WSP (52.5 %) and very poorly in CW (12.4 %). It has been determined that the most important removal mechanism of both 4-NP and 4-t-OP in WWTPs is biodegradation, followed by sorption onto sewage sludge. According to the mass balance performed in advanced biological WWTP, the biodegradation rates for 4-NP and 4-t-OP were found to be 70.4 % and 86.6 %, respectively, while the sorption onto sewage sludge were determined to be 23.3 % and 6.8 %. One of the critical findings obtained within the scope of the study is that while the concentrations of both metabolites, especially 4-NP, in wastewater and sewage sludge, decreased considerably under aerobic conditions, on the contrary, their concentrations increased significantly under anaerobic conditions. Both compounds were detected at higher concentrations in primary sludge compared to secondary sludge in advanced biological WWTP, while in WSP, they were determined at higher concentrations in anaerobic stabilization pond sludge compared to facultative stabilization pond sludge. Besides, it was also determined that the sorption behavior of these alkylphenols is much more dominant than desorption.

Exploring fecal sludge treatment technologies in humanitarian settings at Cox’s Bazar, Bangladesh: a comprehensive assessment of treatment efficiency through characterization of fecal sludge

IntroductionEfficient treatment of fecal sludge in densely populated settings is essential as it has a direct impact on public health and the environment. This study presents a comprehensive assessment of fecal sludge treatment technologies in Rohingya camps at Cox’s Bazar, Bangladesh, focusing on removal efficiencies and compliance with regulatory standards.MethodsSeventeen treatment plants of five different technologies were evaluated based on removal efficiency and standard discharge guidelines for various physicochemical and microbiological parameters.ResultsWaste Stabilization Pond (WSP) was the top performer compared to four other different treatment technologies evaluated, achieving notable removal rates: 97.3% reduction in E. coli, 100% in helminth eggs, 98.3% for COD, 97.8% for BOD, 98.7% for TSS, 92.1% for TS, 82.8% for phosphate, and 93.3% for total nitrogen. Lime Stabilization Ponds showed lower removal rates, except for E. coli (98.9%), with reductions of 99.7% for helminth eggs, 81.6% for COD, 80.9% for BOD, 86.3% for TSS, 68.6% for TS, and 49.2% for phosphate. Upflow Filters demonstrated good removal efficiencies for E. coli (99.7%), TSS (95.9%), COD (91.7%), BOD (93.5%), and helminth eggs (93.7%). WSP consistently outperformed other technologies across all seasons. Despite these, none of the technologies fully met discharge standards.DiscussionThese findings highlight the need for a comprehensive approach, the combination of physicochemical and biological processes, to enhance efficacy. Promoting improved fecal sludge management technologies through awareness campaigns and technical support can mitigate environmental health risks in densely populated humanitarian settings.

Effectiveness of natural herbs on sewage and treated municipal wastewater: A comparative study

Improperly handled sewage is the main cause of water pollution. Nearly 62% of wastewater in urban India remains untreated or partially treated, which further gets disposed of in the natural water bodies. The usual treatment methods include the activated sludge process, oxidation ponds, aerated lagoons, and trickling filters. These methods need spacious areas, a lot of energy and time, which drives up the cost of the treatment. The expense of the treatment process can be decreased by using natural coagulants. The indigenous medical system uses plants, which are abundant in secondary metabolites, to treat a variety of illnesses. The purpose of this study was to comprehend how these indigenous plants can be utilized for treating sewage water, as a low-cost accessible method that can be used by citizens to get access to clean drinking water. Material &amp;amp; Methods: A quick and low-cost method was created to investigate the efficacy of Moringa oleifera (Moringa), Ocimum sanctum (Tulsi), and Azadirachta indica (Neem) in the treatment of sewage water. This herb treated water was then compared to municipal treated water from the Ghatkopar Wastewater treatment facility, managed by the Municipal Corporation of Greater Mumbai (MCGM), Mumbai, India. All the herb-based components were bought from regional markets, and water samples from a lagoon found in the nearby Ghatkopar lagoon in Mumbai. Results: When compared to the lagoon-treated water, the efficacy of the sewage water treated with herbs was higher or comparable. Coliform and copper levels decreased considerably in the treated sample. Herb-treated samples showed a reduction in the Chemical Oxygen Demand (COD) levels as compared to the treated water. Conclusion: When combined, the herbs had a significant impact on lowering the COD, Copper, and coliform levels, making the native plants a valuable source for the treatment of sewage water.

Phytotoxicity of Domestic Effluent Before and After Treatment by Stabilization Ponds

Phytotoxicity tests linked to physicochemical parameters can be used to determine the possible effects of releasing a polluting load into the environment, evaluating the efficiency of a given treatment and its toxicity effects. In this context, the present work sought to evaluate the phytotoxicity of domestic effluent before and after treatment by stabilization ponds, using kale seeds (Brassica oleracea). Toxicity tests were carried out following the methodology of the American Environmental Protection Agency (EPA, 1996) at concentrations of 100%, 80%, 40%, 20%, 10%, and 5%. The seeds were incubated in a B.O.D. incubation chamber for five days at a temperature of 25ºC ± 2ºC. After this period, germination and root elongation were analyzed. The samples were also analyzed for biochemical oxygen demand, temperature, pH, turbidity, color, total solids, ammoniacal nitrogen, and organic nitrogen. Phytotoxicity was statistically evaluated by the Relative Growth Index, T-test (p &lt; 0.05) for samples at 100% concentration, and Kruskal-Wallis followed by Dunn’s test (p &lt; 0.05) to compare the negative control and the different concentrations. As a result, adverse effects of reduced root elongation were observed in samples of raw effluent (100%, 80%, and 20%) and treated effluent (10% and 5%), indicating a tendency toward phytotoxicity. Regarding the physicochemical parameters studied, all were within the established parameters by legislation, and no significant correlation was observed with root elongation. This may indicate the efficiency of stabilization ponds in treating domestic effluents, particularly in reducing phytotoxicity.

Antimicrobial silver nanoparticles derived from Synadenium glaucescens exhibit significant ecotoxicological impact in waste stabilization ponds

Antimicrobial silver nanoparticles derived from Synadenium glaucescens exhibit significant ecotoxicological impact in waste stabilization ponds

Development of a floating constructed wetland for landfill leachate treatment and its potential to remove recalcitrant organic matter

The development of simple and economical treatment technologies for the removal of recalcitrant organic matter is required to achieve long-term and sustainable treatment of landfill leachates in tropical regions. In this study, we evaluated the fundamental properties required to develop the floating constructed wetland (FCW), which consists of a buoyant planting unit made of foamed glass and cattails. The results showed that foamed glass alone can be used as a planting substrate for cattails. Treatment of a synthetic landfill leachate by a lab-scale FCW demonstrated that the test system effectively and continuously removed recalcitrant organic matter, whereas the control system did not. This removal by FCW was shown to proceed through nearly equal contributions from adsorption and potential biological processes. Furthermore, the effect of introducing an FCW in an actual waste landfill site in Thailand was simulated using the parameters obtained from this study. The simulation indicated that the introduction of the FCW into the stabilisation pond was effective in reducing both leachate volume and recalcitrant organic matter. It is important to determine how much of the stabilisation pond should be covered with the FCW for cost-effectiveness. The FCW is expected to contribute to improving long-term, sustainable, and appropriate management of landfill leachate in tropical developing countries.

Integrated assessment of decentralized wastewater treatment plants in semi-arid region in Bolivia

ABSTRACT This study comprehensively evaluates four decentralized wastewater treatment plants intended for agricultural reuse in a semi-arid low-moderate temperature region. It considers environmental, technical, economic, and social perspectives. Anaerobic baffled reactors with hybrid gravel filters (ABR + HGF + VGF) proved the most efficient, with moderate requirements in space, O&amp;M, and energy, albeit the highest treatment cost. Up-flow sludge blanket reactor with activated sludge (UASB + AS) demonstrated high efficiency and compactness, with moderate treatment costs. However, it incurred high energy demands, complex O&amp;M, and more sludge generation. UASB with horizontal gravel filter (UASB + HGF) was among the most land-intensive systems, with moderate costs and O&amp;M requirements, and low energy consumption. However, it fell short of meeting certain environmental criteria. ABR with stabilization ponds (ABR + PONDS) emerged as the most economical, with low energy consumption, but was also among the most land-intensive and failed to achieve adequate effluent quality. Socially, all WWTPs were well accepted for agricultural reuse benefits. In terms of odor perception, UASB + AS and ABR + HGF + VGF exhibit the lowest impact. The Most Appropriate Treatment Technology Index (MATTI) ranked ABR + HGF + VGF and UASB + AS as adequate technologies, while UASB + HGF and ABR + PONDS were poorly adequate. The study recommends a four-dimensional assessment for selecting the most suitable technology, considering the specific context.

Acclimatization of a sequencing batch vertical oxidation pond with simulated agricultural wastewater using duckweed as vegetation: analysis of efficiency, Biomass, and Soil properties.

Vertical oxidation pond operated in sequencing batch mode (HRT: 1.25day) with duckweed as the vegetation was used to acclimatize with simulated agricultural wastewater. The maximum removal rate of urea [371g/(m3.d)] and COD [222.4g/(m3.d)] were observed at moderate concentrations of urea (500mg/L), N-P-K (60mg/L), and pesticide (20mg/L). Inhibition and toxicity posed by higher concentrations, decreased the removals of urea (83% to 61%), COD (81% to 51%), and TDS (76% to 50%) at the end of the acclimatization. Steady removal (> 99%) of PO43--P was observed during acclimatization. Effluent pH increased due to the generation of NH4+-N (maximum 370 ± 5mg/L) from the assimilation of urea. Oxidation of ammonia led to the maximum generation of NO2--N and NO3--N of 10mg/L and 9mg/L, respectively. Particles less than 300μm increased, and both specific gravity (from 2.62 to 2.42) and maximum dry density (from 1.73 to 1.30g/cm3) of the base soil decreased with an increase in urea, N-P-K, and pesticide. Reactor biomass increased (1.42 to 1.90g/L) up to initial concentrations of urea (500mg/L), N-P-K (60mg/L), and pesticide (20mg/L), then decreased (1.68g/L) with an increase in concentration.

Biological treatment of swine wastewater—Conventional methods versus microalgal processes

BackgroundSwine wastewater (SWW) contains abundant organic carbon, nitrogen, and phosphorus, posing a significant risk of pollution and eutrophication with direct environmental release. Therefore, its proper treatment before environmental release is imperative. Conventional SWW treatment methods like stabilization ponds, aerobic processes, and anaerobic digestion are energy-intensive, with limited nitrogen and phosphorus removal and challenges in secondary sludge disposal. MethodsConventional methods described above, in addition to bacterial methods, have been discussed in detail. Microalgal bioremediation is an emerging technology for bioremediation and resource recovery from a circular economy perspective. Significant findingsConventional methods are dissimilatory and do not recover nutrients. On the other hand, the nutrients in SWW serve as a beneficial growth medium for microalgae. With its suitable nutritional composition, the resulting microalgal biomass can serve as supplements for livestock and aquaculture feed, generating additional revenue in microalgae-based SWW treatment. Microalgae-based processes enhance the SWW treatment efficiency and mitigate the common issue of secondary sludge pollution found in conventional treatment methods. This review offers comprehensive insights into traditional and microalgae-based SWW treatment methods and provides a comparative analysis of the various techniques and future research perspectives.

Heavy metals in wastewater and fish collected from waste stabilization pond and human health risks in southwestern Ethiopia

IntroductionThis study aimed to measure the concentration of toxic heavy metals in wastewater samples and Nile tilapia (Oreochromis niloticus) species inhabiting wastewater (waste stabilization ponds) and evaluate their safety as a food source in southwestern Ethiopia. For this purpose, toxic metals like lead (Pb), cadmium (Cd), arsenic (As), and mercury (Hg) in wastewater samples and fish tissues (muscle, gill, and liver) were independently examined.MethodsA laboratory-based cross-sectional study was performed to ascertain the levels of Pb, Cd, As, and Hg in the fish tissues of O. niloticus and wastewater samples. Heavy metal levels were analyzed by microplasma atomic emission spectrometry (Agilent 4210 MP-AES) and hydrogen-generated atomic absorption spectrometry (HGAAS, novAA 400P, Germany).ResultsHeavy metal concentrations were measured in the following decreasing order (µg L−1): Cd &amp;gt; Pb &amp;gt; As &amp;gt; Hg in facultative and maturation ponds, with Cd (27.66 µg L−1) having the highest concentration and Hg (0.349 µg L−1) having the lowest concentration. Among the heavy metals detected in the wastewater samples, Hg showed a statistically significant difference between the sampling points (p = 0.023). The maximum metal concentration was measured for Pb (0.35 mg kg−1) and Cd (0.24 mg kg−1) in the muscle tissue of O. niloticus. The value of arsenic (0.02 mg kg−1) detected in fish edible muscles exceeded the FAO/WHO maximum permissible limit (MPL = 0.01) for human consumption. The carcinogenic and non-carcinogenic health risks of consuming fish due to trace metals were relatively low and posed fewer potential threats to human health. According to this finding, children were more susceptible to heavy metal exposure than adults.ConclusionDue to the high quantities of these harmful heavy metals, wastewater from oxidation ponds should not be used for fishing to avoid bioaccumulation. The target carcinogenic risk (TR) and target hazard quotient (THQ) indicated that all heavy metals were below the safe threshold. This research will provide a baseline for monitoring trace metals in various edible aquatic creatures and for future research in artificial habitats and regulatory considerations.