Hydraulic Loading Rate Research Articles

Effect of integrated microbial fuel cell in a two-stage vertical flow constructed wetland for piggery wastewater treatment and resource recovery by photobioreactor

ABSTRACT This study developed a nature-based pilot-scale technology for simultaneous piggery WW treatment and resource recovery potential. The technology comprised a two-stage vertical flow constructed wetland (2-VFCW) integrated with a microbial fuel cell (MFC) and microalgal photobioreactor. The first and second stage was an unsaturated and saturated type, respectively. The bioelectricity generation was optimised by investigating the suitable electrode zonation, hydraulic retention time (HRT) and WW loading rate. The 2-VFCW-MFC-treated effluent was studied to grow microalgae for biomass production. The 2-VFCW-MFC showed better treatment efficiency than the 2-VFCW, possibly due to enhanced microbial activity on the electrode surface, leading to improved organic matter degradation and electron transfer to the cathode, enhancing NO3− and PO43− reduction. The 2-VFCW-MFC with electrode zonation of 20 cm (cathode) and 60 cm (anode) and HRT of 76 h, 48 min showed the highest open-circuit voltage of 291.83+13.53 mV and WW treatment efficiency. The highest algal biomass of 21,323.34+8,316.26 mg/L (wet weight) was produced at HRT of 96 h, then entered the death phase. Comparatively, the 2-VFCW-MFC showed higher WW treatment efficiency than 2-VFCW at 2 L/day by 23.24% COD, 27.43% TOC, 33.05% PO43−, 13.51% NO3−, 8.14% TN, except TAN (22.71%).

Predicting the impact of underwater skimming on dissolved oxygen consumption in slow sand filters for potable water treatment

In a well-functioning slow sand filter (SSF), dissolved oxygen (DO) is crucial for enabling aerobic processes and microbiota growth. Given that DO supply is predominantly via the feed water, flow pauses (e.g., during cleaning) may trigger anoxic/anaerobic conditions in the stagnant filter bed. Underwater skimming (UWS) is an advanced cleaning technique that employs a skimmer with a shrouded blade, mounted on a mobile platform, to remove the fouling layer composed of sand and particles in order to improve the efficiency of slow sand filtration. As UWS results in changes to the flow pattern of the SSF, a mathematical model was developed to predict DO utilization after a flow perturbation associated with UWS operation. The model was based on a depth resolved measurement of specific oxygen utilization derived from a full scale SSF. Pilot plant experiments monitored DO in the feed and filtrate of SSFs cleaned using underwater and conventional dry skimming techniques. The highest oxygen utilization was in the Schmutzdecke layer, with additional demand imposed by the presence of a granular activated carbon (GAC) sandwich layer. It was observed that pseudo-steady state conditions occurred following filter ripening, where DO utilization, driven by biological activity, remained relatively constant regardless of filter cleaning technique. For flow pauses between three and 24 h, the pause duration's importance decreased, while the hydraulic loading rate became the critical factor for DO recovery in the filter. Additionally, introducing a ‘sweetening flow’ during UWS ensured a continuous DO supply, facilitating quicker DO replenishment post-cleaning. The model reliably predicted filtrate DO within ±0.6 mg/L, demonstrating its operational utility, especially in the optimisation of UWS methodology. As such, UWS can be applied to clean SSFs with the methodology modified to prevent any detrimental effects to DO management within the filter. This study predicted DO dynamics in SSFs, advancing UWS techniques and could be applied for enhancing water treatment strategies by filtration.

Comparative assessment of domestic wastewater treatment via Vermifiltration through various filter bed material.

Vermifilter (VF) is considered sustainable for rural areas; however, filter media is the most important but has been explored less. This study evaluated the performance of vermifilters in treating domestic wastewater (DWW) using various filter media, including areca nutshell (AS), rice straw (RS), dry leaves (DL), and chicken eggshells (ES). We compared the results with four different reactors: R1 (AS), R2 (RS), R3 (DL), and R4 (ES). DWW was applied with a hydraulic loading rate (HLR) of 1 m3/m2/d with Eisenia fetida earthworm species. The results showed the removal of biochemical oxygen demand (BOD) by 82%, 76%, 73%, and 87%; chemical oxygen demand (COD) by 75%, 73%, 72%, and 88%; phosphate by 36%, 25%, 27%, and 50%; sulfate by 56%, 54%, 53%, and 71% in R1, R2, R3, and R4, respectively. Simultaneously, R4 experienced a fivefold reduction in total bacteria and a sixfold reduction in total coliform. Moreover, the most exceptional filter media for vermifiltration is eggshells for the earthworm's growth and treatment efficacy.

Sustainable carbon retention from water input to wetlands at two temporal scales

Wetlands retain carbon from flowing water through biomass accumulation and deposition processes. However, the contributions of accumulated carbon from water to carbon storage and cycling in wetland ecosystems remain unclear. Moreover, there are no comprehensive estimates of the stability and sustainability of wetland performance in retention of carbon from water on different time scales. We conducted a meta-analysis (2889 paired observations) to estimate the stability and sustainability of constructed wetlands in retention of carbon from input water on short and long time scales. This study showed that the efficiency of carbon retention from water in wetlands significantly increased on short time scales, whereas it remained stable on long time scales and among different seasons. The usage of grave, alum sludge and all types of plant had higher effect sizes on short-term wetland water carbon retention, but the long-term stability of water carbon retention was not affected by substrates or plant types. Variations in precipitation as well as air temperature affected the short-term water carbon retention in wetlands, but they did not affect long-term water carbon retention in wetlands. However, on long time scale, the stability of water carbon retention in wetlands was challenged by operation time, low water temperature and high hydraulic load rate, which posed a threat to the sustainability of wetland performance in water carbon retention. In summary, this study demonstrated the stability and sustainability of carbon retention from water and proved the contribution of accumulated carbon from water to the carbon pool in wetland ecosystems.

Synergistic interaction of biochar, Phragmites australis, and rhizosphere microorganisms for enhanced 1,4-dioxane biodegradation

The application of constructed wetlands (CW) system for removing of emerging contaminants from wastewater industry has been recently investigated. However, there is still a research gap in ensuring adequate synergism between aquatic plants and rhizosphere microorganisms for removal of 1,4-dioxane. This research gap was comprehensively addressed here by implementing biochar-amended constructed wetlands (BCWs) for treatment of 1,4-dioxane-laden wastewater, focusing on the biodegradation mechanisms, and associated microbial activity and diversity. Three sequential BCW1, BCW2 and BCW3 units provided an effluent quality of 60.9 ± 20.8 mg/L for chemical oxygen demand (COD), 3.7 ± 0.9 mg/L for 1,4-dioxane, and 5.6 ± 1.9 mg/L for total nitrogen at total hydraulic retention time (HRT) of 1.4 d., and hydraulic loading rate of 178.6 L/m2. d. The main metabolites by-products were ethylene glycol (8.3–13.8 mg/L), glycolaldehyde (6.6–8.3 mg/L), glycolic acid (4.5–8.9 mg/L), and oxalic acid (3.0–6.3 mg/L). Acidobacteriota (3.7 %), Bacteroidota (26.0 %), Chloroflexi (4.6 %), and Proteobacteria (25.5 %) were abundant at the phylum level, whereas Afipia (1.4 %) and Mycobacterium (6.5 %), i.e., dioxane degraders, were dominant at the genus level. The main 1,4-dioxane removal mechanisms were uptake/volatilization by Phragmites australis (40.9 ± 3.8 %) and biodegradation by biofilm-attached biochar (33.04 ± 2.2 %) followed photo-oxidation (16 ± 1.8 %). Hence, biochar/wetlands cultivated by Phragmites australis could be efficiently employed for treatment of dioxane-laden industrial effluents.

CONSTRUCTED WETLANDS FOR NITROGEN REMOVAL AND SIMULTANEOUS REUSE OF DOMESTIC SEWAGE

This study evaluated the behavior of vertical flow constructed wetland (VFCW), planted with irrigated rice (Oryza sativa L.), specie BRS-GO Guará, and a vertical flow soil filter without plant (VFSF-CTR), as control, both on a reduced experimental scale. The objective was the removal and recovery of N from domestic sewage, using soil latossoil red-yellow (LRY) mixed with medium sand (modified LRY) as support medium. The operation of VFCW and VFSF-CTR for ten months and two rice crop cycles, used three different hydraulic loading rates - HLR (4.0, 8.0 and 15.0 cm/d); with three repetitions, totalizing eighteen experimental units. For the VFCW, the total Kjeldahl nitrogen (KTN) and N-NH4+ removal efficiencies, ranged from 86% to 95%; and, for VFSF-CTR, from 79 to 94%; with the rice crop favoring higher efficiencies in KTN removal, independent of HLR. Both systems showed tertiary treatment removal efficiency in a single stage; in addition, the variations in the removal efficiencies were minimal when operated with HLR of 15 cm/d. There was great accumulation of KTN and mineral N (N-NH4+ and N-NO3-) in soil, mainly in the 0-5 cm soil layer, which can be used for fertilization of other crops. There was also N immobilised in microbial biomass (MBN). This rapid fertilisation improved the soil quality in a short term (ten months of sewage application) and provided the production of grains and vegetable biomass for human and animal food. The VFCW presented good results, either operated with low or high hydraulic loads, showing larger operational flexibility.

Novel overlapping constructed wetlands with water drops reoxygenation and lightweight fillers for decentralized wastewater treatment

Constructed wetlands (CWs), crucial for the rural decentralized wastewater treatment, have encountered limitations in nutrient removal efficiency and require extensive land area. This study has constructed a novel overlapping horizontal subsurface flow CWs (OLCWs). Remarkably, OLCWs with mixed lightweight fillers (M-OLCWs) exhibited a significant enhancement in total nitrogen (TN) removal efficiency (88–91 %) in different hydraulic loading rates compared to single filler OLCWs (48–62 %). This significant enhancement can be attributed to the lightweight fillers, which have higher abundances and diversity of nitrogen related microorganisms. The treatment dynamics revealed that the second stage exhibited an excellent TN removal efficiency (73–75 %) attributed to sufficient dissolved oxygen concentration by water drops reoxygenation. The research reveals that M-OLCWs, by utilizing water drops reoxygenation and lightweight fillers, not only enhance pollutant treatment efficiency but also reduce required land area, thereby offering a sustainable solution for rural decentralized wastewater treatment.

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.

Optimizing nutrient utilization, hydraulic loading rate, and feed conversion ratios through freshwater IMTA-aquaponic and hydroponic systems as an environmentally sustainable aquaculture concept

Water quality in land-based fish production can be controlled through either instantaneous water exchange or costly wastewater treatment followed by recirculation. Agricultural-aquaculture integration is an excellent alternative technique for reducing nutrient discharge levels, boosting profitability, and converting fish culture wastewater into valuable products. The current study employed a solar energy system to power two separate IMTA-aquaponics systems (Nutrient Film Technique, NFT, and Floating Raft Systems, FRS) for the cultivation of Nile tilapia, African catfish, thin-lipped grey mullet, freshwater crayfish, freshwater mussels, and a variety of vegetables. Tilapia and catfish were fed exclusively on diets under the IMTA system. All wastewater from tilapia and catfish ponds, both dissolved and solid, flows sequentially to ponds containing other cultivated species. The water then flows through the IMTA system's terminal point to the NFT and FRS systems before returning to the tilapia and catfish ponds, allowing complete control of the nutrient flow throughout this entire circular system. Two 147-day production cycles were concluded. The results from the second production cycle are reported. Total biomass gain for aquatic species in the IMTA system was 736.46 kg, compared to 145.49 kg in the tilapia and 271.01 kg in the catfish monoculture systems. The current IMTA system had a cumulative feed conversion ratio (FCR) of 0.90, while the FCRs for tilapia and catfish were 1.28 and 1.42, respectively. Nile tilapia and catfish consumed 571.90 kg of feed containing 25.70 kg of nitrogen (N) and 9.70 kg of phosphorus (P), reflecting, and gaining 11.41 and 3.93 kg of dietary N and P, representing 44.40 and 40.46% dietary N and P retention, respectively. In the IMTA system, the addition of mullet and prawn as detrivores aquatic animals improves dietary N and P utilization efficiency to 59.06 and 51.19%, respectively, while the addition of mussels as herbivore animals improves dietary N and P utilization efficiency to 65.61 and 54.67%, respectively. Finally, using FRS and NFT as hydroponic systems increased dietary N and P efficiency to 83.51% N and 96.82% P, respectively. This study shows that the IMTA-Aquaponic system, as a bio-integrated food production system, can convert the majority of fish-fed residues into valuable products suitable for desert, rural, and urban areas in impoverished and developing countries.

Ferrate as a coagulant prior to sand filters treating secondary wastewater effluent for reuse.

Wastewater reuse is one of the crucial water resources in Egypt due to the ongoing need to increase water resources and close the supply-demand gap. In this study, a new coagulant has been investigated before sand filters as an advanced wastewater treatment method. The sand filter pilot was run at a hydraulic loading rate of 0.75 m/h and two different dosages of three coagulants (Alum, FeCl3, and Ferrate VI) were selected using the jar tests. The sand filter without coagulant removed 12% of BOD5 and 70% of turbidity. Applying in-line coagulation before the sand filter provided effluents with better quality, especially for turbidity, organics, and microorganisms. Ferrate provided the highest removal of turbidity (90%) and BOD5 (93%) at very low dosages and lower costs compared with other coagulants, however, it adversely impacted both conductivity and dissolved solids. A significant effect on reducing bacteria was obtained with 40.0 mg/L of alum. According to the study's findings, the ferrate coagulant enhanced the sand filter's performance producing effluents with high quality, enabling it to meet strict water reuse regulations as well as aquatic environmental and health preservations.

Assessment of the effectiveness of a full-scale trickling filter for the treatment of municipal sewage in an arid environment: Multiple linear regression model prediction of fecal coliform removal

In response to water scarcity, Morocco faces the challenge of using treated wastewater for irrigation purposes. This study evaluates the efficiency of a full-scale trickling filter (TF) system in Imintanout, Morocco. The system consists of three septic tanks, two TFs, and secondary decanters. Over a 5-year period, the system showed significant reductions in pollutants: 98 % of TSS, 94 % of BOD5, 98 % of COD, 41 % of TP, and 88 % of NH4+, with these reductions being statistically significant at the 95 % confidence level. A multiple linear regression (MLR) model successfully predicted the removal of fecal coliform (FC) by the TF, and a reduction of 2.88 log units was achieved. High cos2 values indicated the importance of hydraulic loading rate (HLR), BOD5, and FC, which were particularly affected by seasonal variations. Positive correlations between FC and TSS in certain periods highlight the seasonal variability in the composition of urban wastewater, which is effectively captured by the MLR model (R2 = 0.77). Although the treated water complied with Moroccan discharge standards, its high nitrate (140 mg L−1) and FC (4.32 log units) levels made it unsuitable for reuse in agricultural and landscape irrigation, as they exceeded safety limits. This work highlights the importance of optimizing treatment systems to produce high quality reclaimed water, which is essential to meet the challenges of water scarcity.

A Comparative Performance Assessment of the Integrated Upflow and Surface Flow-Based Constructed Wetlands Dosed with Landfill Leachate: Electrode Coupling and Input Load Variation

This study reports organic, nutrient, and coliform removal performances of two integrated wetlands designed to treat landfill leachate. Each integrated system included two components: a normal or electrode-integrated upflow-based wetland and a surface flow wetland (with internal baffle walls). The components were fully or partially filled with stone dust media and planted with Canna indica. Two hydraulic loading rates, i.e., 15 L and 60 L (per day), were applied. The integrated wetlands achieved a mean biochemical oxygen demand (BOD), chemical oxygen demand (COD), total nitrogen (TN), total phosphorus (TP), and coliform removal efficiency ranges of 89–94%, 95–97%, 85–91%, 91–98%, and 70–88%, respectively, within the applied loading ranges. The electrode-dependent system achieved better pollutant removal performances due to the influence of electrochemical-based bioreactions that fostered microbial decomposition. Nitrogen accumulation percentage (with respect to observed removal) in plant tissues ranged between 0.6 and 25%; phosphorus accumulation percentage was negligible, i.e., ≤0.009%. The chemical composition of the stone dust media supported nutrient adsorption. Stable nutrient removal performance was observed with both systems despite variable loading ranges due to pollutant removal in the upflow-based wetlands followed by controlled flow direction (induced by baffle walls) in the surface flow wetlands that triggered chemical and biological removals. Mean power density production ranged between 235 and 946 mW/m3 with the electrode-based integrated wetland system. In summary, this study demonstrates the application of integrated wetland systems to treat landfill leachate and the associated factors to achieve stable removal under variable loading ranges.

Estimating Drainage from Forest Water Reclamation Facilities Based on Drain Gauge Measurements

A growing human population requires sustainable solutions to regulate and dispose of municipal wastewater. Water treatment facilities in northern Idaho are permitted to apply reclaimed wastewater to forest land during the growing season at specified monthly hydraulic loading rates. We assessed the spatial and temporal variability of drainage below the rooting zone between non-irrigated (control) and irrigated (effluent) stands during the growing and dormant seasons in 2021. No drainage was observed during the two months of annual seasonal drought, but large magnitudes of drainage were recorded during the dormant season (38–94 cm), which was consistent with seasonal precipitation. The overall effect of effluent treatment on the drain gauge measurements did not differ from the controls, as effluent only increased the drainage at some facilities. The measured drainage averaged from 35 to 62 cm among facilities. We then used the drainage measurements to calibrate hydrological models (Hydrus-1D and Water Erosion Prediction Project [WEPP]) and predict the drainage in 50 measurement plots distributed evenly among five forest water reclamation facilities. As with the observed drainage, there were no statistically significant growing season differences in the predicted monthly drainage during the growing season between the effluent and control plots, suggesting the successful use of hydrologic models to support the measured drainage findings. While both models struggled to accurately predict the quantity of drainage during the dormant season, they both successfully predicted that drainage would continue through May. WEPP also successfully predicted that the treated plots began to drain in September and October following late-season irrigation at some facilities. The models showed that the prescribed crop coefficient used by the Idaho Department of Environmental Quality was adequate in avoiding drainage during the peak summer months.

Characterization and Performance of Peanut Shells in Caffeine and Triclosan Removal in Batch and Fixed-Bed Column Tests.

Peanut shells' adsorption performance in caffeine and triclosan removal was studied. Peanut shells were analyzed for their chemical composition, morphology, and surface functional groups. Batch adsorption and fixed-bed column experiments were carried out with solutions containing 30 mg/L of caffeine and triclosan. The parameters examined included peanut shell particle size (120-150, 300-600, and 800-2000 µm), adsorbent dose (0.02-60 g/L), contact time (up to 180 min), bed height (4-8 cm), and hydraulic loading rate (2.0 and 4.0 m3/m2-day). After determining the optimal adsorption conditions, kinetics, isotherm, and breakthrough curve models were applied to analyze the experimental data. Peanut shells showed an irregular surface and consisted mainly of polysaccharides (around 70% lignin, cellulose, and hemicellulose), with a specific surface area of 1.7 m2/g and a pore volume of 0.005 cm3/g. The highest removal efficiencies for caffeine (85.6 ± 1.4%) and triclosan (89.3 ± 1.5%) were achieved using the smallest particles and 10.0 and 0.1 g/L doses over 180 and 45 min, respectively. Triclosan showed easier removal compared to caffeine due to its higher lipophilic character. The pseudo-second-order kinetics model provided the best fit with the experimental data, suggesting a chemisorption process between caffeine/triclosan and the adsorbent. Equilibrium data were well-described by the Sips model, with maximum adsorption capacities of 3.3 mg/g and 289.3 mg/g for caffeine and triclosan, respectively. In fixed-bed column adsorption tests, particle size significantly influenced efficiency and hydraulic behavior, with 120-150 µm particles exhibiting the highest adsorption capacity for caffeine (0.72 mg/g) and triclosan (143.44 mg/g), albeit with clogging issues. The experimental data also showed good agreement with the Bohart-Adams, Thomas, and Yoon-Nelson models. Therefore, the findings of this study highlight not only the effective capability of peanut shells to remove caffeine and triclosan but also their versatility as a promising option for water treatment and sanitation applications in different contexts.

Sustainability of global small-scale constructed wetlands for multiple pollutant control

The global wastewater surge demands constructed wetlands (CWs) to achieve the UN’s Sustainable Development Goals (SDG); yet the pollutant removal interactions and global sustainability of small CWs are unclear. This study synthesizes small CW data from 364 sites worldwide. The removal efficiency of organic matter and nutrient pollutants of small CWs had a 75th percentile of 68.8–84.0%. Bivariate analysis found consistent synergies between pollutant removals, lasting 3–12 years. The optimal thresholds for maintaining the synergistic effects were as follows: area size—17587 m2, hydraulic loading rate—0.45 m/d, hydraulic retention time—8.2 days, and temperature—20.2 °C. When considering the co-benefits and sustainability of small CWs for multi-pollutants control, promoting small-scale CWs could be an effective and sustainable solution for managing diverse wastewater pollutants while simultaneously minimizing land requirements. This solution holds the potential to address the challenges posed by global water scarcity resulting from wastewater discharge and water pollution.

Use of recycled construction and demolition waste as substrate in constructed wetlands for the wastewater treatment of cheese production

Recycled building debris has recently emerged as a suitable wetland infill substrate due to its low density, exceptional water absorption capabilities, and high porosity. This study investigated, for the first time, the use of construction demolition wastes (CDW), and rock processing residues (RPR) as substrate materials in vertical-horizontal flow hybrid constructed wetlands for the treatment of cheese production wastewater. Results showed that the use of both CDW as well as RPR, as substrate material, provided an equal or even better quality of treated wastewater compared to the conventional use of gravel as a substrate. High removal efficiencies were recorded for turbidity (CDW: 91–92%, RPR: 97%), solids (CDW: 85–88%, RPR: 96–97%), organic matter (CDW: 79–84%, RPR: 96–98%), and total phosphorus (CDW: 72–76%, RPR: 87%) for both examined recycled materials. During the experiment, different loadings rates (HLR) were tested: 25 mm d−1 and 37.5 mm d−1. Radiological measurements indicate that, their use did not cause toxic effects on the environment, as the amounts of radioactivity found in the effluent of the systems are not significant. Increasing the hydraulic loading rate appeared to have no negative effect on pollutant removal, as the systems and plants were fully acclimated and mature. This approach offers several advantages, including the use of readily available and abundant waste material, potential cost savings, and the environmental benefits of recycling CDW and RPR instead of disposing of them in landfills.

Subsurface wastewater infiltration systems for nitrogen pollution control.

Subsurface wastewater infiltration systems (SWISs) are suggested to be a cost-effective and environmentally friendly method for sewage treatment. However, a comprehensive summary of the relevant mechanisms and optimization methods for nitrogen (N) removal in SWIS is currently lacking. In this review, we first summarize the N transformation mechanisms in SWIS. The impact of operational parameters on the N removal efficiency is then delineated. To enhance pollutant removal and minimize resource wastage, it is advisable to maintain a wet-dry ratio of 1:1 and a hydraulic loading rate of 8-10cm/day. The organic load should be determined based on influent characteristics to optimize the balance between sewage treatment and nitrous oxide (N2O) emission. Finally, various strategies and modifications have been suggested to enhance pollutant removal efficiency and reduce N2O emissions in SWIS, such as artificial aeration, supply electron donors, and well-designed structures. Overall, greater emphasis should be placed on the design and management of SWIS to optimize their co-benefits while effectively controlling N pollution. PRACTITIONER POINTS: SWISs are often considered black boxes with their efficiency depending on hydraulic characteristics, biological characteristics, and substrate properties. Biological nitrification coupled with denitrification is considered to be the major N removal process. Increasing the reduction of N2O to the inert N2 form is a potential mechanism to mitigate global warming. Strategies such as artificial aeration, supply electron donors, and well-designed structures are suggested to improve N removal performance.

Effective nutrient removal from aquaculture wastewater utilizing an indoor nutrient film technique hydroponic system

AbstractAquaculture wastewater treatment must remove nutrients to prevent eutrophication of receiving waters and to allow for possible re‐use of the treated water. This study aims to evaluate the shoot and root growth of crops produced in Nutrient Film Technique hydroponic systems and treat aquaculture wastewater using phytoremediation. The average physico‐chemical parameters of the aquaculture wastewater during the study period were pH 6–6.4, temperature 25°C–27°C, EC 0.7–0.8 mS/cm, and total dissolved solids (420–560 ppm). The operating conditions of hydroponic treatment units were hydraulic loading rate of 857.28 m/day, hydraulic retention time of 0.3 h, organic loading rate of 12567.8 Ibs‐BOD5/ft^2/day (BOD5 is 5 – day Biochemical Oxygen Demand) and flow rate of 54 L/h. The study found that the average elimination efficiency of nitrate‐nitrogen in aquaculture wastewater treatment varied from 78.28% by Money plants (Epiprennum aureum), 71% by Crotons (Codiaeum varigatum), 70.25% by Arrowhead plants (Syngonium podophyllum), 67.25% by Purple Heart (Tradescantia pallida), 68.62% by for Spinach (Spinacea oleracia), and 42.85% by Brinjal plants (Solanum melongena). The average removal effectiveness of BOD5 varied from 71.07% by Money plants (Epiprennum aureum), 68.62% by Crotons (Codiaeum varigatum), 78% by Arrowhead plants (Syngonium podophyllum), 72% by Purple Heart (Tradescantia pallida), 68% by Spinach (Spinacea oleracia), and 70% by Brinjal plants (Solanum melongena). Thus, environmentally friendly and economically advantageous method for reducing and removing nitrate‐nitrogen and BOD5 from aquaculture effluent is hydroponic phytoremediation. The promising potential of using indoor NFT hydroponic systems for nutrient removal particularly nitrate‐nitrogen, from aquaculture wastewater. Each plant species is assessed for its ability to uptake and reduce nitrate‐nitrogen levels, growth patterns, and overall suitability for wastewater treatment. The study emphasizes the eco‐friendly and sustainable wastewater management nature of the proposed method.

Varying removal of emerging organic contaminants in drinking water treatment residue-based biofilter systems: Influence of hydraulic loading rates on microbiology

Drinking water treatment residue (DWTR)-based biofilter is an environment-friendly and cost-effective technology for eliminating nutrients and emerging organic contaminants (EOCs) from natural water. This study explored the removal efficiencies of five trace-level EOCs and the associated microbial response of biofilm in two identical DWTR-based biofilters under varying hydraulic loading rate (HLR) conditions over six months of operation. The results showed that the most recalcitrant EOC (carbamazepine) was mainly removed by DWTR adsorption (7.8–11.0 ng g−1), while the response of the biofilm community to HLR significantly affected the degradation of 17α-ethinylestradiol, sulfamethoxazole, roxithromycin, and sulfathiazole (P < 0.001). A higher HLR significantly stimulated the production of extracellular polymeric substance and increased the stochasticity and diversity of community assembly, improving denitrification and the removal efficiency of DWTR-based biofilm for biodegradable roxithromycin (80 %) and sulfamethoxazole (76 %). In contrast, lower HLR led to carbon limitation and exerted substrate selection pressures, resulting in more deterministic and stable community assembly, with keystone species such as Bacillus enriched in EOC degradation-related functional genes. Moreover, co-occurrence network analysis revealed a simpler but more intensive interaction network among EOC degraders under the lower HLR condition. This interaction network facilitated the co-metabolism of influent organic carbon and the removal of more recalcitrant contaminants, 17α-ethinylestradiol (48 %) and sulfathiazole (37 %). This study offered a novel insight into biofilter management from a hybrid perspective of environmental microbiology and engineering science, highlighting the dynamic adaptation of microbes to specific EOC degradation under varying HLR conditions.

The banana tree circle as a nature-based solution for sustainable greywater management: A new design model.

The banana tree circle (BTC) is a low-cost system for local greywater management, using a natural treatment and disposal process, providing additional resource recovery benefits. However, there are no standard design criteria for BTC that would allow for quality control of its efficiency and sustainability, and little is currently known about the full-scale performance of BTC. Based on the scoping literature review of 31 documents in the scientific database and eight documents from grey literature, a standard design model was proposed for the BTC technology based on the concept of water balance, greywater flows, rain, infiltration, and evapotranspiration. The first two steps of the BTC design were determining the areas required for infiltration and evapotranspiration. A cylindrical form trench, the soil percolation rate, and the hydraulic loading rate were considered for the infiltration area. The banana trees' evapotranspiration rate was taken into consideration for the evapotranspiration area. The proposed model was applied in a case study where we used a trench with 0.8 m depth and 1.5 m diameter. This study proposes a standard design criterion for the BTC based on environmental factors, and the scoping of the literature provides the basis for future studies to evaluate its environmental sustainability.