Nitrification characteristics and microbial community changes during conversion of freshwater to seawater in down-flow hanging sponge reactor.

In recirculating aquaculture systems (RAS), maintaining water quality in aquaculture tanks is a paramount factor for effective fish production. A down-flow hanging sponge (DHS) reactor, a trickling filter system used for water treatment of RAS that employs sponges to retain biomass, has high nitrification activity. However, nitrification in seawater RAS requires a long start-up time owing to the high salinity stress. Therefore, this study aimed to evaluate the nitrification characteristics and changes in the microbial community during the conversion of freshwater to seawater in a DHSreactor fed with ammonia-based artificial seawater. The total ammonia nitrogen concentration reached 1.0 mg-N·L-1 (initial concentration 10 mg-N·L-1) within 11 days of operation, and nitrate production was observed. The 16 S rRNA gene sequence of the DHS-retained sludge indicated that the detection rate of the ammonia-oxidizing archaeon Candidatus Nitrosocosmicus decreased from 23.9 % to 14.0 % and 25.8-17.6 % in the upper and lower parts of the DHS reactor, respectively, after the introduction of seawater. In contrast, the nitrite-oxidizing bacteria Nitrospira spp. increased from 0.1 % to 9.5 % and from 0.5 % to 10.5 %, respectively. The ammonia oxidation rates of 0.12 ± 0.064 and 0.051 ± 0.0043 mg-N·g-MLVSS-1·h-1 on the 37th day in the upper and bottom layers, respectively. Thus, nitrification in the DHS reactor performed well, even under high-salinity conditions with short operational days. This finding makes the transition from freshwater to saltwater fish in the RAS system simple and economical, and has the potential for early start-up of the RAS.

Low-cost, reliable, and highly efficient removal of COD and total nitrogen from sewage using a sponge-filled trickling filter.

Development of low-cost and reliable reactors demanding minimal supervision is a need-of-the-hour for sewage treatment in rural areas. This study explores the performance of a multi-stage sponge-filled trickling filter (SPTF) for sewage treatment, employing polyethylene (PE) and polyurethane (PU) media. Chemical oxygen demand (COD) and nitrogen transformation were evaluated at hydraulic loading rates (HLRs) ranging from 2 to 6 m/d using synthetic sewage as influent. At influent COD of ∼350 mg/L, PU-SPTF and PE-SPTF achieved a COD removal of 97% across all HLRs with most of the removal occurring in the first segments. Operation of PE-SPTF at an HLR of 6 m/d caused substantial wash-out of biomass, while PU-SPTF retained biomass and achieved effluent COD < 10 mg/L even at HLR of 8-10 m/d. The maximum Total Nitrogen removal by PE-SPTF and PU-SPTF reactors was 93.56 ± 1.36 and 92.24 ± 0.66%, respectively, at an HLR of 6 m/d. Simultaneous removal of ammonia and nitrate was observed at all the HLRs in the first segment of both SPTFs indicating ANAMMOX activity. COD removal data, media depth, and HLRs were fitted (R2 > 0.99) to a first-order kinetic relationship. For a comparable COD removal, CO2 emission by PU-SPTF was 3.5% of that of an activated sludge system.

Integration of down-flow hanging sponge reactor to oreochromis niloticus - Brassica oleracea aquaponics system.

Aquaponics is a promising solution for addressing food security concerns. Nonetheless, an effective water-purification system is necessary to achieve high and stable yields of fish and vegetables. This study aimed to evaluate the nitrification and oxygen transfer performance of a laboratory-scale down-flow hanging sponge (DHS) reactor with a Brassica oleracea aquaponics system to treat water in an Oreochromis niloticus closed-aquaculture system. The DHS reactor showed a higher oxygen transfer coefficient (KLa) than the conventional aerator and provided an adequate dissolved oxygen (DO) concentration of approximately 5.5 mg/L essential for O. niloticus growth throughout the experimental period. The evaluated DHS-based aquaponic system maintained high water quality in an aquaculture tank, with a survival rate of 97%. The O. niloticusgrew at a low feed conversion ratio of 1.5-2.1 and a low feeding rate of 0.5% at high stocking densities of 17.5-22.2 kg-fish-weight/m3. 16S rRNA gene sequencing indicated that the DHS sponge carrier effectively retained nitrifying bacteria such as Nitrosomonas and Nitrospira. This study demonstrated that the DHS reactor provided a high DO concentration and that a simultaneous DHS reactor with a hydroponic tank provided a low-cost aquaponic system that could be applied for food production in the aquaculture industry.

Trickling filter systems for sustainable water supply: An evaluation of eco-environmental burdens and greenhouse gas emissions.

Despite the global water crisis, the significant potential of trickling filter systems as a crucial auxiliary option for sustainable water supply has received insufficient attention. Therefore, this study presents the first-ever evaluation of the environmental impacts of trickling filter application in wastewater treatment, focusing on eco-environmental burdens. Additionally, the study explores greenhouse gas emissions, energy, and exergy footprints, providing novel insights into the environmental implications of using trickling filters for wastewater treatment. The study's findings indicate that the consumption of heat and electricity in trickling filters has significant environmental impacts, particularly on land use (93.24%), freshwater/marine eutrophication (∼81.98%), and human health (45.36%). The majority of the energy required for trickling filter operation is supplied by fossil fuels (96.02%), resulting in increased greenhouse gas emissions (65.58%). The exergy of trickling filters is highly efficient, accounting for over 95% of the system's energy. Mathematical modeling reveals that anaerobic digestion and secondary clarifier have the highest energy consumption, with contributions of 94.65% and 2.63%, respectively. Construction expenses account for almost 88% of the total cost, with anaerobic digestion (42.15%) and trickling filters (35.39%) being the most costly components. The cost of treating 1 m3 of wastewater is estimated at 0.52 $/m3. Sensitivity analysis demonstrates that electricity (14.66%) and heat (18.65%) significantly impact terrestrial ecotoxicity and land use, respectively. This study presents a framework for future investigations in this field.

Effect of trickling filter on carbon and nitrogen removal in vertical flow treatment wetlands: A full-scale investigation.

Vertical Flow Treatment Wetland (VF-TW) systems achieve high efficiencies in terms of carbon related parameters removals from domestic wastewaters. Nitrogen removal is also efficient but optimisations are still needed. This article reports and discusses experimental data collected from 24-h monitoring campaigns of 29 full-scale VF-TWs, having different configurations and operation time up to 13 years. All monitored systems gathered 1 or 2 stage(s) of unsaturated or partially saturated VF-TW. Additionally, some of those included an aerobic biological Tricking Filter (TF) prior to TW stage(s). Results firstly showed that the implementation of a TF improved TSS, COD and BOD5 removal rates in the monitored systems. Regarding nitrogen removal, the association of TF with one stage of partially saturated vertical TW was found to achieve around 79% of nitrification in average and up to 92% in some cases. In the configurations where TF was associated to 2 successive stages of TW, almost all total nitrogen removal by nitrification/denitrification was achieved at the outlet of the first-stage TW. The contribution of the second-stage TW in denitrification was found very low due to limited availability of organic carbon to support heterotrophic denitrification. Specific solutions to enhance the contribution of the second stage in the denitrification process are discussed.

Simultaneous denitrification and desulfurization-S0 recovery of wastewater in trickling filters by bioaugmentation intervention based on avoiding collapse critical points.

In order to better achieve efficiently simultaneous desulfurization and denitrification/S0 recovery of wastewater, the intervention of sulfur oxidizing bacteria (SOB) and denitrifying bacteria (DNB) was employed to avoid the collapse critical points (the dramatically decrease of S/N removal efficiency) under the fluctuated load. With the assistance of DNB and SOB, collapse critical point of trickling filter (TF) was delayed from the P8 (105-114 d) to P10 stage (129-138 d). The treatment efficiency of nitrogen and sulfur was the highest with the S/N ratio of 3:1. The bioaugmentation of DNB and SOB at collapse critical point could effectively regulated collapse situation, which further increased the maximum system utilization/elimination capacity to 4.50 kg S m-3·h-1 and 0.90 kg N m-3·h-1 (increased by 56.89% and 65.56% in comparison to control). High-throughput sequencing analysis indicated that Proteobacteria (average 78.59%) and Bacteroidetes (average 9.30%) were dominant bacteria in the reactor at all stages. As the reaction proceeds, the microbial community was gradually dominated by some functional genera such as Chryseobacterium (average 2.97%), Halothiobacillus (average 22.71%), Rhodanobacter (average 14.02%), Thiobacillus (average 9.01%), Thiomonas (average 16.70%) and Metallibacterium (average 21.63%), which could remove nitrate or sulfide. Both of Principal Component Analysis (PCA) and Canonical Correlation Analysis (CCA) demonstrated the important role of DNB/SOB during the long-term run in the trickling filters (TFs).

Enhanced Degradation of Naproxen by Immobilization of Bacillus thuringiensis B1(2015b) on Loofah Sponge.

The naproxen-degrading bacterium Bacillus thuringiensis B1(2015b) was immobilised onto loofah sponge and introduced into lab-scale trickling filters. The trickling filters constructed for this study additionally contained stabilised microflora from a functioning wastewater treatment plant to assess the behavior of introduced immobilized biocatalyst in a fully functioning bioremediation system. The immobilised cells degraded naproxen (1 mg/L) faster in the presence of autochthonous microflora than in a monoculture trickling filter. There was also abundant colonization of the loofah sponges by the microorganisms from the system. Analysis of the influence of an acute, short-term naproxen exposure on the indigenous community revealed a significant drop in its diversity and qualitative composition. Bioaugmentation was also not neutral to the microflora. Introducing a new microorganism and increasing the removal of the pollutant caused changes in the microbial community structure and species composition. The incorporation of the immobilised B1(2015b) was successful and the introduced strain colonized the basic carrier in the trickling filter after the complete biodegradation of the naproxen. As a result, the bioremediation system could potentially be used to biodegrade naproxen in the future.

Evaluation of a pilot-scale bio-trickling filter as a VOCs control technology for the chemical fibre wastewater treatment plant.

The performance of lab- and pilot-scale bio-trickling filters (BTFs) for the treatment of emissions from a chemical fibre wastewater treatment plant was investigated. These systems were installed mainly to demonstrate the effectiveness of bio-trickling technologies in purifying exhaust gases containing different kinds of volatile organic compounds (VOCs). Results showed that 12 days more were necessary for the pilot-scale BTF to start up successfully than the lab-scale one. Both the lab- and pilot-scale BTFs exhibited contaminant removal efficiency higher than 90% at an empty bed residence time of 59 s, corresponding to gas flow of 0.2 m3 h-1 and 550 m3 h-1, respectively. The reduction of the microelement in the nutrient solution had little effect on the performance of the pilot-scale BTF. The abundance and diversity of the microorganism analysis showed that the diversity of the contaminants had a significant influence on the microorganism distribution in the BTF. Economic feasibility study showed that BTF might be an efficient solution for VOCs control with a lower cost than adsorption technology and regenerative catalytic oxidation.

Combined chemically enhanced primary sedimentation and biofiltration process for low cost municipal wastewater treatment.

The main objective of wastewater treatment is to remove carbon and other nutrients from municipal and industrial effluents in order to protect the environment and human health. Typical wastewater treatment is usually achieved by a combination of physical, chemical and biological methods. In this work, municipal wastewater was depurated using chemically enhanced primary treatment (CEPT) in combination with a pilot-scale trickling filter. Lab scale experiments (Jar-tests) were carried out in order to determine the optimum dosage of chemicals. Selection criteria were the organic load removal efficiency and the low operational cost. Coagulation-flocculation process was conducted through polyaluminium chloride (PAC) and the cationic polyelectrolyte (Zetag 8180) addition. By combining CEPT and trickling filter, tCOD (total Chemical Oxygen Demand), sCOD (soluble Chemical Oxygen Demand), BOD5 (5-day Biochemical Oxygen Demand), NH4+-N, TSS (Total Suspended Solids), VSS (Volatile Suspended Solids) and PO43--P removal efficiencies were estimated to be 89, 82, 93, 60, 96, 96 and 78%, respectively. It is concluded that biological filtration contributed significantly in nutrients removal processes. Moreover, the obtained effluent was low in carbon and rich in nitrogen, which can be applied for restricted irrigation after disinfection, complying with the discharge limits set in the Greek Joint Ministerial Decree 145116/2011.

Bioavailability of wastewater derived dissolved organic nitrogen to green microalgae Selenastrum capricornutum, Chlamydomonas reinhardtii, and Chlorella vulgaris with/without presence of bacteria.

Effluent dissolved organic nitrogen (DON) is problematic in nutrient sensitive surface waters and needs to be reduced to meet demanding total dissolved nitrogen discharge limits. Bioavailable DON (ABDON) is a portion of DON utilized by algae or algae+bacteria, while biodegradable DON (BDON) is a portion of DON decomposable by bacteria. ABDON and BDON in a two-stage trickling filter (TF) wastewater treatment plant was evaluated using three different microalgal species, Selenastrum capricornutum, Chlamydomonas reinhardtii and Chlorella vulgaris and mixed cultured bacteria. Results showed that up to 80% of DON was bioavailable to algae or algae+bacteria inoculum while up to 60% of DON was biodegradable in all the samples. Results showed that C. reinhardtii and C. vulgaris can be used as a test species the same as S. capricornutum since there were no significant differences among these three algae species based on their ability to remove nitrogen species.

An overview of biological processes and their potential for CO2 capture.

The extensive amount of available information on global warming suggests that this issue has become prevalent worldwide. Majority of countries have issued laws and policies in response to this concern by requiring their industrial sectors to reduce greenhouse gas emissions, such as CO2. Thus, introducing new and more effective treatment methods, such as biological techniques, is crucial to control the emission of greenhouse gases. Many studies have demonstrated CO2 fixation using photo-bioreactors and raceway ponds, but a comprehensive review is yet to be published on biological CO2 fixation. A comprehensive review of CO2 fixation through biological process is presented in this paper as biological processes are ideal to control both organic and inorganic pollutants. This process can also cover the classification of methods, functional mechanisms, designs, and their operational parameters, which are crucial for efficient CO2 fixation. This review also suggests the bio-trickling filter process as an appropriate approach in CO2 fixation to assist in creating a pollution-free environment. Finally, this paper introduces optimum designs, growth rate models, and CO2 fixation of microalgae, functions, and operations in biological CO2 fixation.

Biological manganese oxidation by Pseudomonas putida in trickling filters.

Biological oxidation has been researched as a viable alternative for treating waters with high manganese (Mn) concentrations, typically found in mine drainage or in some geological formations. In this study, laboratory-scale trickling filters were constructed to compare the Mn removal efficiency between filters inoculated with the Mn oxidizing bacteria, Pseudomonas putida, and filters without inoculation. Manganese oxidation and removal was found to be significantly greater in trickling filters with Pseudomonas putida after startup times of only 48 h. Mn oxidation in Pseudomonas putida inoculated trickling filters was up to 75% greater than non-inoculated filters. One-dimensional advective-dispersive models were formulated to describe the transport of Mn in trickling filter porous media. Based on the experimental transport parameters obtained, the model predicted that a filter depth of only 16 cm is needed to reduce influent concentration of 10 mg L(-1) to 0.05 mg L(-1).

Distinct comammox Nitrospira in high-rate down-flow hanging sponge reactor treating municipal wastewater.

A down-flow hanging sponge (DHS) reactor is a trickling filter system used for wastewater treatment, which employs sponges to retain biomass. This study assessed the process performance of a compact DHS combined with a sedimentation tank with seven phases at varying hydraulic retention times (HRT) over 500 days. The BOD of the DHS effluent was maintained at 4.0 ± 0.5 mg·L-1 for the shortest HRT 0.3 ± 0.1 h. The nitrification efficiency was considerably impacted by the reduced HRT, with NH4+-N and NO3--N concentrations of 9.0 ± 1.2 mgN·L-1 and 2.2 ± 0.5 mgN·L-1, respectively. Nevertheless, the effluent complied with effluent discharge standards throughout the trial period. The number of comammox 16S rRNA gene copies ranged from 5.58 to 13.2 × 107 copies·mL-1, indicating that sponges biomass retained carrier can provide favorable conditions for comammox growth and could contribute to nitrification in the high-rate DHS reactor.

Cellulosimicrobium sp. Strain L1: A Study on the Optimization of the Conditions and Performance of a Combined Biological Trickling Filter for Hydrogen Sulfide Degradation.

Sulfide is a toxic and hazardous substance in the agricultural environment, which can cause damage to humans and livestock when exposed to large amounts of air. In this study, we performed one-factor optimization of the culture conditions and culture fractions of the Cellulosimicrobium sp. strain L1 and combined it with a biological trickling filter cell for the degradation of hydrogen sulfide for 24 consecutive days. The degradation effect of strain L1 and the biological trickling filter (BTF) on hydrogen sulfide was investigated, and the changes in intermediate products in the degradation process were briefly analyzed. The results showed that strain L1 had the highest conversion efficiency when incubated with 3 g/L sucrose as the carbon source and 1 g/L NH4Cl as the nitrogen source at a temperature of 35 °C, an initial pH of 5, and a NaCl concentration of 1%. The concentration of thiosulfate increased and then decreased during the degradation process, and the concentration of sulfate increased continuously. When strain L1 was applied to the biological trickling filter, it could degrade 359.53 mg/m3 of H2S. This study provides a deeper understanding of sulfide degradation in biological trickling filters and helps promote the development of desulfurization technology and the treatment of malodorous gasses produced by the accumulation of large quantities of livestock manure.

Behaviour of pharmaceuticals and endocrine disrupting chemicals in simplified sewage treatment systems.

This work assessed the behaviour of nine pharmaceuticals and/or endocrine disrupting chemicals (EDCs) in demo-scale upflow anaerobic sludge blanket reactors (UASB reactors) coupled to distinct simplified post-treatment units (submerged bed, polishing ponds, and trickling filters) fed on raw sewage taken from a municipality in Brazil. The dissolved concentration of the studied micropollutants in the raw and treated sewage was obtained using solid phase extraction (SPE) followed by analysis in a liquid chromatography system coupled to a hybrid high resolution mass spectrometer consisting of an ion-trap and time of flight (LC-MS-IT-TOF). The UASB reactors demonstrated that they were not appropriate for efficiently removing the assessed compounds from the sewage. Furthermore, this study demonstrated that the hydraulic retention time (HRT) was an important parameter for the removal of the hydrophilic and less biodegradable compounds, such as trimethoprim and sulfamethoxazole. The post-treatment units substantially increased the removal of most target micropollutants present in the anaerobic effluents, with a greater removal of micropollutants in simplified systems that require a large construction area, such as the submerged bed and polishing ponds, probably because of the higher HRT employed. Alternatively, compact post-treatment systems, such as trickling filters, tended to be less effective at removing most of the micropollutants studied, and the type of packing proved to be crucial for determining the fate of such compounds using trickling filters.

Evaluation of leachate treatment by trickling filter and sequencing batch reactor processes in Ibadan, Nigeria.

Strong and highly polluting leachate is continuously discharged into Omi stream and its tributaries in Ibadan, southwest Nigeria, from a municipal solid waste landfill. Previous studies have targeted physical and chemical treatment methods, which could not be implemented on site as stand-alone treatment systems. This study explored the bench-scale, trickling filter (TF) and sequencing batch reactor (SBR) treatment processes and assessed the quality of effluents produced. Leachate treatment using TF produced effluents with significant reductions (%) in suspended solids (SS) (73.17%), turbidity (71.96%), biochemical oxygen demand (BOD5) (76.69%) and ammonia (NH3) (59.50%), while SBR produced effluents with reductions in SS (62.28%), BOD5 (84.06%) and NH3 (64.83%). The dissolved oxygen of the reactors was 4.7 and 6.1mg/l, respectively, in TF and SBR. Also, NH3 values reduced marginally; however, nitrification took place significantly, but within permissible limits. The effluents produced by biological treatment processes were better in quality though the mean residual concentrations for colour, SS and dissolved solids; BOD5 and iron were above the national regulatory standards for discharge into surface water bodies. SBR gave a better effluent quality and should be combined with other treatment methods in sequence to produce quality effluents.

Synthetic microbial consortia to enhance the biodegradation of compost odor by biotrickling filter.

Composting generates odorous gases, including ammonia (NH3), hydrogen sulfide (H2S), and volatile organic compounds (VOCs). The Biological Trickling Filter (BTF) is effective for odor treatment, but it may have limitations with hydrophobic VOCs. In this study, a strain of Bacillus subtilis with ammonia-reducing ability, a strain of Bacillus cereus with desulfurization ability and a strain of Schizophyllum commune with the ability to degrade dimethyl disulfide were isolated and screened. The three strains were combined to create synthetic microbial consortia for enhancing odor treatment in the BTF. Compared to the activated sludge control, the BTF with synthetic microbial consortia removed 92.43% ammonia, 92.75% hydrogen sulfide. Furthermore, it demonstrated a significant improvement in the removal rates of p-methyl mercaptan, methyl sulfide, and dimethyl disulfide. High-throughput sequencing was conducted on the fillers of the synthetic microbial consortia-inoculated BTF to analyze the microbial community composition.

Life cycle assessment and cost-benefit analysis of internal-stack trickling bio-electrochemical reactor: an evaluation for commercial viability.

The present study reports a detailed life cycle assessment and cost-benefit analysis of a commercially viable Internal-Stack-Trickling Bio-Electrochemical Reactor (IS-TrickBER). IS-TrickBER used wastewater as a feedstock and converted that wastewater through electrochemical methods into low-grade fertilizer and produced electricity. IS-TrickBER was observed for its performance in terms of power output and wastewater treatment. IS-TrickBER exhibited up to 4.2 Wh net energy yield while treating 84.84L wastewater per day along with 92.17% COD removal and 38.23% Columbic efficiency during the operational run with real municipal wastewater. Based on daily net energy yield, up to 1457.6Wh yearly net energy yield can be expected. A comprehensive start-to-end life cycle assessment study associated with the manufacturing, and operational phases of IS-TrickBER was also conducted to ascertain its impact on the environment. The environmental impact through air emissions during the manufacturing stage can be minimized by changing the plastic balls used as packing material in the reactor. A detailed cost-benefit analysis was also conducted to understand its economic viability. Cost-benefit analysis of IS-TrickBER, based on net energy yield, shows that IS-TrickBER could compensate its installation cost within a few years. IS-TrickBER performed well in eliminating the chemical load of wastewater and simultaneous electricity generation. Due to its scalability, compactness, and low maintenance, IS-TrickBER can be a suitable candidate in real-time wastewater treatment.

Nature-based solutions for wastewater treatment and bioenergy recovery: A comparative Life Cycle Assessment.

The aim of this study was to assess the environmental impacts of up-flow anaerobic sludge blanket (UASB) reactors coupled with high rate algal ponds (HRAPs) for wastewater treatment and bioenergy recovery using the Life Cycle Assessment (LCA) methodology. This solution was compared with the UASB reactor coupled with other consolidated technologies in rural areas of Brazil, such as trickling filters, polishing ponds and constructed wetlands. To this end, full-scale systems were designed based on experimental data obtained from pilot/demonstrative scale systems. The functional unit was 1 m3 of water. System boundaries comprised input and output flows of material and energy resources for system construction and operation. The LCA was performed with the software SimaPro®, using the ReCiPe midpoint method. The results showed that the HRAPs scenario was the most environmentally friendly alternative in 4 out of 8 impact categories (i.e. Global warming, Stratospheric Ozone Depletion, Terrestrial Ecotoxicity and Fossil resource scarcity). This was associated with the increase in biogas production by the co-digestion of microalgae and raw wastewater, leading to higher electricity and heat recovery. From an economic point of view, despite the HRAPs showed a higher capital cost, the operation and maintenance costs were completely offset by the revenue obtained from the electricity generated. Overall, the UASB reactor coupled with HRAPS showed to be a feasible nature-based solution to be used in small communities in Brazil, especially when microalgae biomass is valorised and used to increase biogas productivity.

A new hybrid ensemble approach for the prediction of effluent total nitrogen from a full-scale wastewater treatment plant using a combined trickling filter-activated sludge system.

In this study, different K-nearest neighbors (KNN), support vector regression (SVR), decision tree (DT), and random forest (RF) algorithms integrated with the Bayesian optimization algorithm (BOP) have been applied as novel hybrid modeling/optimization tools to predict the total nitrogen in treated wastewater of Southern Tehran Wastewater Treatment Plant (STWWTP). In order to enhance the outcomes of hybrid models, the chosen sub-models (the best and least correlated hybrid models) were used to generate voting average and stacked regression ensemble models. Throughout the preprocessing step, two alternative scenarios were used to handle missing values from the samples, including elimination versus estimation via linear interpolation. The results of this research demonstrated that ensemble models were better than individual hybrid models, although not all ensemble models were superior to single models. The results also revealed that the stacking regression ensemble model using KNN-BOP and SVR-BOP as sub-models was the most superior model among the developed models, with the coefficient of determination (R2) = 0.640, root mean squared error (RMSE) = 2.378, and mean absolute error (MAE) = 1.838 on the test data. The best hybrid ensemble model that can accurately predict the concentration of total nitrogen (TN) in the effluent can give people a heads-up about water pollution caused by eutrophication before it gets bad.