Total Kjeldahl Nitrogen Removal Research Articles

Influence of Organic Loading Rates on the Treatment Performance of Membrane Bioreactors Treating Saline Industrial Wastewater

This study investigated the efficacy of membrane bioreactor (MBR) technology in treating saline industrial wastewater, focusing on the impact of the organic loading rate (OLR) and the food-to-microorganism (F/M) ratio on treatment performance. This research utilized saline industrial wastewater from Al-Hasa, which had salinity levels ranging from 5000 to 6900 mg/L. It explored treatment processes at varying Chemical Oxygen Demand (COD) concentrations of 800, 1400, and 2000 mg/L, corresponding to an OLR of 0.80 ± 0.05, 1.41 ± 0.07, and 1.98 ± 0.12 g COD/L, respectively. The average F/M ratios used were 0.20, 0.36, and 0.50 g COD/g MLSS·d, maintaining a constant Sludge Residence Time (SRT) of 12 days, a hydraulic retention time (HRT) of 24 h (hrs.), and a flux of 10 L/m2·h. The MBR system demonstrated high COD removal efficiencies, averaging 95.7 ± 1.6%, 95.5 ± 0.4%, and 96.1 ± 0.3%, alongside Biochemical Oxygen Demand (BOD) removal rates of 98.3 ± 0.2%, 99.8 ± 0.1%, and 98.5 ± 0.1%, respectively. However, an increased OLR led to elevated residual COD and BOD levels in the treated effluent, with COD concentrations reaching 34.2 ± 12.8, 63.3 ± 5.9, and 76.5 ± 5.4 mg/L, respectively. This study also reveals a significant decline in ammonia and Total Kjeldahl Nitrogen (TKN) removal efficiencies as OLR increases, dropping from 96.1 ± 0.5% to 80.2 ± 0.9% for ammonia and from 83.8 ± 3.4% to 65.8 ± 2.3% for TKN. Furthermore, higher OLRs significantly contribute to membrane fouling and elevate the transmembrane pressure (TMP), indicating a direct correlation between OLRs and operational challenges in MBR systems. The findings suggest that for optimal performance within the Saudi disposal limits for industrial wastewater, the MBR system should operate at an F/M ratio of ≤0.33 g COD/g of Mixed Liquor Suspended Solid (MLSS)·d. This study underscores the critical role of the OLR and F/M ratio in treating saline industrial wastewater using MBR technology, providing valuable insights for enhancing treatment efficiency and compliance with environmental standards.

A hybrid BOA-SVR approach for predicting aerobic organic and nitrogen removal in a gas-liquid-solid circulating fluidized bed bioreactor

This study introduces the hybrid of the Bayesian optimization algorithm and support vector regression (BOA-SVR) models to predict the removal of aerobic organic (total chemical oxygen demand, COD) and nitrogen compounds such as total Kjeldahl Nitrogen (TKN), ammonium nitrogen (NH4-N), and nitrate nitrogen (NO3-N) from municipal wastewater in a gas-liquid-solid circulating fluidized bed (GLSCFB) bioreactor. GLSCFB bioreactors treat wastewater by removing nutrients biologically. The downer of a GLSCFB bioreactor provided experimental data on TKN, NH4-N, NO3-N, and TCOD removal. The hybrid optimal intelligence algorithm (BOA-SVR) has improved model accuracy across multiple domains by combining BOA and SVR. The coefficient of determination (R2), residual, mean absolute error (MAE), root mean square error (RMSE), and fractional bias (FB) were used to analyze BOA-SVR model performance. The models match experimental data from four operational stages well, with R2 or adj R2 values above 0.99 for all responses. The model's accuracy was confirmed by relative deviations and residual plots showing dispersion around the zero-reference line. The BOA-SVR model consistently predicted dependent variables with low RMSE and MAE values (≤ 2.24 and 2.21, respectively) and near-zero FB. Computing efficiency was shown by optimizing TCOD, TKN, NH4-N, and NO3-N models in 70.61, 72.89, 74.37, and 54.07 s. A rigorous test on unseen data with different noise levels confirmed the model's stability. Furthermore, BOA-SVR performs better than traditional multiple linear regression (MLR). Overall, the BOA-SVR model predicts biological nutrient removal in municipal wastewater utilizing a GLSCFB bioreactor quickly, correctly, and efficiently, reducing experimental stress and resource use.

Biochar as ammonia exchange biofilm carrier for enhanced aerobic nitrification in activated sludge

The effects of biochar on aerobic nitrification in activated sludge were investigated in sequencing batch reactors. Biochar amended reactors exhibited 87–94 % lower ammonia in effluent and 16–71 % greater removal of total Kjeldahl nitrogen compared to control reactors. Quantitative qPCR analyses revealed that the relative abundance of ammonia oxidizing bacteria (AOB, amoA/16S rRNA genes) was greater in biochar than in control reactors. AOB were enriched on biochar surfaces, with biochar particles having up to 12.1 times greater relative abundance of AOB compared to suspended biomass. Biochar’s maximum ammonia sorption capacity of 4.4 mg N/g at pH 7 decreased with decreasing pH, however a pH-sensitive fluorescent probe was used to show that biofilms growing on biochar surfaces maintain a median pH of > 6.7 despite reactor acidification by nitrification. Microbial colonization of biochar in activated sludge creates a pH-sheltered environment that sustains biochar’s ammonia sorption capacity, resulting in enrichment of AOB on biochar particles and improved nitrification.

Optimization of pollutants removal from anaerobically digested dairy wastewater by electro-oxidation process: a response surface methodology modeling and validation

The release of anaerobically digested dairy wastewater (ANDDW) without a treatment can lead to severe environmental pollution, prompting the exploration of effective and sustainable treatment methods. Amidst various wastewater treatment approaches, the electro-oxidation (EO) process is considered as a promising, clean, and adaptable solution. In this study, the major operational parameters viz. current density, electrolyte concentration, treatment time, and mixing speed of an EO comprising Ti/PbO2 anode and stainless-steel cathode, were optimized using response surface methodology (RSM) for efficient removal of chemical oxygen demand (COD), ammonia nitrogen (NH3-N), total phosphorus (TP), orthophosphate (OP), total nitrogen (TN), and total Kjeldahl nitrogen (TKN) from ANDDW. Optimal conditions were identified as a current density of 90 mA cm−2, 0.08% electrolyte concentration, 180 min treatment time, and 400 rpm mixing speed. Under the optimum conditions, the COD, NH3-N, TP, OP, TN, and TKN removal efficiencies were 78.36, 63.93, 87.41, 92.39, 67.01, and 81.42%, respectively. Furthermore, the reaction rate followed the first-order kinetic model for the pollutants removal with correlation coefficients (R2) close to 1. The findings highlight the potential of using the EO process to treat high pollutant-laden ANDDW and encourage further studies to confirm the corresponding outcomes on a pilot scale.Graphical abstract

Total phosphorus and total Kjeldahl nitrogen removal using an aerobic granular sludge process. Case studies ANN and RSM modeling

Removing nutrients from wastewater is essential because high concentrations in aquatic systems lead to severe eutrophication problems, the most common impairment of surface waters such as lakes and oceans. Total phosphorus (TP) and total Kjeldahl nitrogen (TKN) were removed from mixed wastewater using an aerobic granular sludge process in a sequencing batch reactor (AGS-SBR). An artificial neural network (ANN) and response surface methodology (RSM) were applied to evaluate the main parameters of the process. For TKN removal, only cycle time (CT) (0.0475) was a significant variable, achieving removal efficiencies of up to 81%. In TP case removal, two parameters, VER and AR, were substantial for this process, completing elimination efficiencies of around 40%. On comparing the models with statistical indices, ANN coupled with the moth-flame optimization algorithm (ANN-MFO) demonstrated higher performance with an adjusted R2 (0.9866) for the case of TP removal and (0.9519) for TKN removal.

Nutrients removal by high-rate activated sludge and its effects on the mainstream wastewater treatment

Conventional wastewater treatment technologies often involve energy-intensive processes, creating a need for more sustainable and efficient solutions. The high-rate activated sludge (HRAS) process, characterized by short sludge and hydraulic retention times, demonstrates proficient chemical oxygen demand (COD) removal with minimal oxidation and energy expenditure, positioning it as a promising approach for achieving energy-efficient wastewater treatment.This study addresses the nutrient removal efficiency of a demonstration-scale pilot plant (35 m3·d-1) operating for 497 days. It investigates the correlation between nutrient removal efficiencies, COD fractions, and suspended solids removal in real wastewater, without primary clarification.The process consistently achieves average removal efficiencies: 23% for total Kjeldahl Nitrogen (TKN), 7.3% for N-NH4+, 56% for total phosphorus (TP), and 11% for P-PO43-. The superior TP removal is attributed to the high particulate influent fractions (81%), underscoring the pivotal role of settling efficiency. The HRAS process effectively controls TP peak values, although its influence on TKN peaks is somewhat limited. This underscores HRAS's proficiency in mitigating phosphorus spikes in influent wastewater. In contrast, the lower TKN removal is associated with diminished particulate inlet fractions (46%).Nutrient removal mechanisms in HRAS mirror those of COD, primarily revolving around adsorption and entrapment processes, as opposed to conventional biological pathways. It also highlights the independence of oxidized COD, nitrogen, and phosphorus removal. Furthermore, a comprehensive analysis of the COD/TKN within HRAS effluent unveils the presence of a short-cut nitrification/denitrification process, supplemented by Anammox in the sidestream, as the most suitable pathway for downstream nitrogen removal. This revelation signifies a substantial advancement and positions HRAS as a potential initial stage of a partial nitritation/Anammox (PN/A) process within mainstream wastewater treatment.

Boosting methane production and raw waste activated sludge treatment in a microbial electrolysis cell-anaerobic digestion (MEC-AD) system: The effect of organic loading rate

This study deals with the effect of different organic loading rates (OLRs) on the organic load removal and the productivity of methane, in a microbial electrolysis cell-anaerobic digestion (MEC-AD) system treating raw waste activated sludge (WAS). For comparison, two identical reactors, a control (AD) and a MEC-AD reactor were constructed. Both reactors operated for 131 days, during which different Organic Loading Rates (OLRs) were examined; 1.1, 1.7 and 2.9 gCOD/(L*d). The results showed that the MEC-AD reactor performed better, relative to the AD reactor, at high OLRs. Specifically, the additional total particulate carbon and Kjeldahl nitrogen removal reached 12% and 13%, respectively, at an OLR of 1.7 gCOD/(L*d), while they reached 19% and 13%, respectively, at an OLR of 2.9 gCOD/(L*d). Moreover, the biogas production and the methane content increased by 30% and 6%, respectively, at an OLR of 1.7 gCOD/(L*d) and by 32% and 5%, respectively, at an OLR of 2.9 gCOD/(L*d). The electrochemical measurements indicated that the power output increased from 5 to 30 mW/m2 when the OLR increased from 1.1 to 2.9 gCOD/(L*d). Overall, the results showed that the MEC-AD accelerated and enhanced the WAS treatment, boosting methane productivity.

Effect of co-culturing bacteria and microalgae and influence of inoculum ratio during the biological treatment of tannery wastewater

This present investigation is carried out to study the effect of algal and bacterial inoculum concentrations on the removal of organic pollutants and nutrients from the tannery effluent by the combined symbiotic treatment process. The bacterial and microalgal consortia was developed in laboratory setup and mixed together to perform this study. The Influence of algae and bacteria inoculum concentrations on the removal of pollutants such as Chemical Oxygen Demand (COD) and Total Kjeldahl Nitrogen (TKN) were studied using statistical optimization through Response surface methodology. For the design of experimental set up and optimization, full factorial Central composite design was used. The profiles of pH, Dissolved Oxygen (DO) and nitrate were also monitored and studied. The inoculum concentrations of microalgae and bacteria showed significant effect on Co-culturing on COD, TKN and nitrate removals as major response. The linear effect of bacterial inoculum has positive dominant influence on COD and TKN removal efficiencies. Nitrate utilization by microalgae increases with the increase in microalgal inoculum concentration. The maximum removal efficiencies of COD and TKN with 89.9% and 80.9% were obtained at optimum bacterial and algal inoculum concentrations of 6.7 g/L and 8.0 g/L respectively. These outcomes of this study are immensely favorable for maximizing the COD and nitrogen (nutrients) removal capabilities of microalgae-bacterial consortia in tannery effluent.

Bio-communal wastewater treatment plant real-time modeling using an intelligent meta-heuristic approach: A sustainable and green ecosystem

Considering the importance of nitrogen and organic carbon in supporting the growth of various algae and organic matters, that improves eutrophication along the water bodies. It is, therefore, essential to develop reliable tools that can help policymakers and experts in-understand the environmental and aquatic importance of these macronutrients in relation to other different hydro-physical and chemical variables. The current research proposes the development of three different data intelligence; Neuro-fuzzy (NF), Support Vector Regression (SVR), and Multivariate Regression (MVR) model integrated with a hybrid Neuro-fuzzy-Shuffled frog-leaping algorithm (NF-SFLA) for the simulation of total Kjeldahl Nitrogen (TKNeff) and total organic carbon (TCODeff) based-organic removal from wastewater treatment plant (WWTP). Both visualized and numerical performance of the single models indicated that NF model combination two (NF-M2) showed superior performance than other models for modeling TKNeff (MAE = 0.0367, NSE = 0.9110) and TCODeff (MAE = 0.0363, NSE = 0.8300). The hybrid NF-SFLA was proposed to improve the performance prediction of both TKNeff and TCODeff from the WWTP effluent. The NF-SFLA-M2 achieves an overwhelming performance improvement of up to 13 % over NF-M2 for TKNeff and TCODeff regarding NSE criteria.

Taguchi method in the optimization of municipal wastewater treatment by electrocoagulation integrated with zeolite

Electrocoagulation integrated with zeolite in a single step was efficiently applied to the treatment of municipal wastewater with saline water infiltrate. In the first part, the influence of the initial pH values of the solutions and the addition of natural zeolite and NaCl electrolyte on the removal efficiency was investigated. Decreasing of electrical conductivity (17.00–65.79%), turbidity (61.28–97.44%), chemical oxygen demand (77.08–92.71%) and total Kjeldahl nitrogen (33.33–90.48%) was obtained. The initial pH of the wastewater, the addition of zeolite and NaCl electrolyte shows a significant influence on the turbidity reduction, total Kjeldahl nitrogen removal, electrode consumption, and settling properties, while its effects on chemical oxygen demand and electrical conductivity reduction is less pronounced. An increase in solution temperature is higher in an acidic (pH = 4) medium and is related to higher electrode consumption. In the second part, Taguchi’s L9 orthogonal array method was used to optimize​ municipal wastewater treatment by electrocoagulation and zeolite addition. The effects of initial pH values (pH = 9, pH = 4, and without initial pH adjustment), zeolite addition (natural, synthetic and without), electrolyte addition (NaCl and Na2SO4 and without), and experiment duration time (15, 30 and 45 min) on chemical oxygen demand and turbidity were examined. The results of Taguchi optimization revealed that the most effective factor for the chemical oxygen demand removal is zeolite addition, while the initial pH is for turbidity. Optimal conditions for chemical oxygen demand and turbidity are: the initial pH = 4, without adding electrolyte and an experimental duration of 15 min. However, the addition of zeolite has a dissimilar effect on chemical oxygen demand and turbidity. For chemical oxygen demand, better results are obtained using synthetic zeolite and for turbidity without any type of zeolite.

Production of nanopore structure bio-adsorbent from wood waste through a self-sustained carbonization process for landfill leachate treatment

The discharge of leachate poses a serious risk to both surface water and groundwater from landfills. As rainwater and moisture seep through waste in landfills, it will release leachate which is high in concentration of organic matter and ammonium nitrogen. Adsorption process using activated carbon was used as one of the tertiary treatment processes in the landfill. This paper presents the utilization of biomass-based adsorbents to substitute the current activated carbon in the landfills. The carbonization process was employed using a 3-tonne self-sustained pool-type reactor, to produce micropores biochar as bio-adsorbent. The carbonization proceeds for 48 h using feedstocks with different initial moisture content of 20% and 40%. The biochar produced had microporosity ranging from 1.8 to 15.4 nm and a surface area of 192.9–231 m2/g. The use of biochar for landfill leachate treatment has shown satisfactory results, with COD, ammoniacal nitrogen, and total Kjeldahl nitrogen removal at 73%, 70%, and 97%, respectively, and heavy metals content value below the Malaysian discharge limits. This exemplifies the potential of biochar as a bio-adsorbent for treating landfill leachate and the feasibility of up-scaling biochar production from wood waste.

Strategies for enhancing phosphorous removal in Vertical Flow Constructed Wetlands.

Constructed wetlands (CWs) are among the fastest emerging treatment methods for wastewater treatment. Unlike their organics and nitrogen removal capacities, the potential of CWs as a sink for phosphorous is still debatable. In this study, the secondary data from several CWs treating domestic sewage were compiled and assessed. Curves were plotted between orthophosphate-phosphorous (PO43--P) loading and the corresponding removal rates. Other factors affecting PO43--P removal like depth of the CW, surface area, organic loading rate etc. Were also analyzed. Removal rates of PO43--P were conforming to a linear positive relation with the loading rates. Pea gravel as a CW medium performed consistently well (60-80% removal) for a wide range of influent PO43--P loading (0.5-1.5g/m3-d). The increased depth of the wetland appears to favor phosphate removal. PO43--P removal was found to be correlated with outlet dissolved oxygen, total Kjeldahl nitrogen removal and effluent nitrate. The study suggests that proper design, optimal organic loading and suitable pre-treatment may increase the applicability of CWs for phosphate removal from domestic wastewater. Larger area requirements can also be avoided by increasing their depth while keeping the volume of the filter media the same.

Performance of Porous Substrates for Domestic Wastewater Treatment under Prolonged Hydraulic Retention Time

Physicochemical characteristics of porous substrates (longan biochar, corn biochar, and pumice) including specific surface area (SSA), pore volume (Vp), and cation exchange capacity (CEC) were determined. Longan biochar had the highest SSA, Vp, and CEC, followed by corn biochar and pumice. Then, columns filled with each of these 3 substrates together with gravel as a control treatment, were evaluated to compare wastewater treatment efficiency under different hydraulic retention times (HRTs). Each system had been acclimatized with wastewater for 8 weeks. Then, influent and effluent were analyzed at 1, 3, 5, and 7 day intervals. Water analysis revealed that biochar-based systems showed higher dissolved oxygen (DO) development and greater removal of biochemical oxygen demand (BOD5), total suspended solids (TSS), ammonium (NH4-N), total Kjeldahl nitrogen (TKN), and nitrate (NO3-N) than pumice and gravel-based systems. Prolongation of HRT significantly increased NO3-N removal and slightly increased BOD5 and TSS removal. Both BOD5 and TSS removal in biochar-based systems after 1 day HRT was about 93–94% while they significantly increased with HRT extension to a high of 97–98%. Furthermore, NO3-N removal in biochar-based systems increased from 47–48% after 1 day HRT to 80% after 5–7 days HRT. In addition, NH4-N and TKN removal was influenced by both substrate and HRT with significant interaction between these two factors. Longan biochar-based systems, in particular eliminated almost 90% of both NH4-N and TKN and the removal efficiency improved significantly after HRT was extended. Meanwhile, both NH4-N and TKN removal were only 20–30% in the gravel-based systems and 50-60% in pumice-based system. The study suggests that longan biochar is the most effective substrate. Longer HRTs were also found to increase the efficiency of removing organic matter and nitrogen.

Nitrogen and organic load removal from anaerobically digested leachate using a hybrid electro-oxidation and electro-coagulation process

This study evaluated the performance of an integrated electrochemical process, which simultaneously utilizes electro-oxidation (EO) and electro-coagulation (EC) methods while removing organic and nitrogen loads from high-strength leachate obtained from anaerobic digesters. A bipolar arrangement of the aluminum electrode, sandwiched between a monopolar boron-doped diamond anode and stainless-steel cathode, integrates EC and EO into a single reactor. This arrangement demonstrated an enhancement of 33%, 27%, and 24% in removal capacity for ammonia nitrogen (AN), total Kjeldahl nitrogen (TKN), and total nitrogen, respectively, when compared to just EO at 0.8 A current intensity after 24 h. Increasing the current intensity from 0.4 A to 1.0 A enhanced the organic nitrogen and AN removal. Chemical oxygen demand (COD) exhibited initial faster removal kinetics with higher current intensities and eventually reached 95%–98% removal for intensities of 0.6 A or higher. Additional removal for AN, TKN were also observed with increasing current intensity. Lowering the pH further expedited the COD removal kinetics. Reducing and maintaining the pH at 4, 6, and 8 by dosing of hydrochloric acid (HCl) resulted in the 100% removal of AN and TKN from the integrated system in 6, 8, and 20 h, respectively. Accelerated removal of COD and the enhanced removal of AN and TKN through pH control could be linked to the formation of active chlorine species in bulk solution. The integrated system offered lower energy consumption than EO due to oxidation on the additional anodic surface of the bipolar electrode, as well as the adsorption-precipitation of contaminants in aluminum flocs.

Influence of organic loading rates on treatment performance of membrane bioreactor treating tannery wastewater

Tannery wastewater contains high pollutants concentrations such as nitrogen, organic matter, salinity, toxic metals, etc. Membrane bioreactor has been widely recognized as potential technology for wastewater treatment and reuse. Finding proper operating conditions and a strategy for fouling mitigation in MBR process is essential to application to tannery wastewater treatment. Herein, this study investigated the effect of organic loading rate (OLR) on the performance and fouling behavior of membrane bioreactor (MBR) treating tannery wastewater during 280 days of operation. The MBR was operated under the low fluxes of 4.2 and 8.3 L m−2 h−1, corresponding to organic loading rates of 1.3 (OLR1) and 2.6 kg COD m−3d−1 (OLR2). The results show that the COD removal was obtained at 78 ± 19% and 89 ± 2% for OLR1 and OLR2, respectively. For the former condition the average removal of total Kjeldahl nitrogen (TKN) and NH4+-N reached 53%–68% and 58%–70%. TKN removal was mainly contributed by cell assimilation. Incomplete nitrification was due to high TDS (11,000–16,790 mg L−1) and the presence of free ammonia ( 6.77–31.11 mg L−1) concentrations under pH 8.7–8.8. Membrane fouling rate was strongly governed by operated flux. At flux of 4.2 LMH the fouling rate was as low as 0.19–0.4 kPa d−1 while the fouling rate accelerated (1.87–1.93 kPa d−1) as increased two times flux . These findings proposed a low flux of 4.2 LMH for MBR operation in treating real tannery wastewater. It was found that influent total suspended solids (TSS) played a crucial factor in spiking mixed liquor suspended solids (MLSS) into MBR. Thus, a pretreatment process is suggested to remove major suspended solids from raw tannery wastewater prior to biological treatment.

Bench scale demonstration of greywater treatment in a 3-stage sequential process comprising anaerobic, aerobic, and vertical greenery system

Non-potable reuse of treated greywater (GW) within households can reduce daily freshwater consumption and provide water security. Urban household in India was estimated to discharge 38–45 L GW/capita·day with an average composition of (mg/L) COD 238.05; total Kjeldahl nitrogen (TKN) 31.08; total phosphorus (TP) 2.85; anionic surfactants (AS) 0.5 and faecal coliform log 6.09 CFU/100 mL, etc. A 100 L/day bench-scale, 3-stage sequential GW treatment process was optimized and its long-term performance was demonstrated with synthetic GW feedstock corresponding to the aforementioned characteristics. The treatment process comprises a multi-chambered upflow anaerobic biofilm reactor (AnBR) followed by an upflow aerobic reactor (AeR) and vertical greenery system (VGS) inhabited by flowering creeper Sphagneticola trilobata. At steady-state HRT of ~2.25 day the process achieved the following pollutant removal (as %) COD 93.23; turbidity (NTU) 98.75; total nitrogen (TN) 54.23; TP 96.42; AS 92.97; faecal coliform: 99.95 when fed with an average influent characteristics of (mg/L) COD 281, TN: 24.41, TP 1.13, AS 16.66, faecal coliform 6 log CFU/100 mL, pH 8.85, NTU 63.3. The predominant removal of COD and AS took place in AnBR and AeR respectively, whereas, VGS demonstrated relatively higher removal of turbidity, TKN, and faecal coliforms. The inefficient nitrification-denitrification in AeR was attributed to a lower influent C/N ratio of 3.18. The acclimatization of VGS to the tertiary treatment process exhibited an aerial biomass production rate of 5063.37 mg TS/m2·d. The treated water attained the standards for household recycling as prescribed by WHO.

Simultaneous Carbon and Nitrogen Removal from Domestic Wastewater using High Rate Vermifilter.

Being a cost-effective and environmentally benign technology, vermifiltration has significantly replaced the available conventional wastewater remediation methods in many cases over the last few decades. The present work emphasizes on the investigation of the nitrogen transformation dynamics, in addition to the organic carbon abatement in the designed high rate hybrid vermifilter. Moreover, the economical sustainability of the vermifiltration technology has also been enlightened by creating a bridge with the concept of circular bio-economy. The designed high rate macrophyte-assisted vermifilter (MAVF) ascertained significant high nitrogen and organic carbon removal efficiencies from the real domestic sewage, considering the chemical oxygen demand (COD) of the influent and hydraulic loading rate (HLR) as the input variables. The designed MAVF facilitated the maximum ammonium nitrogen (NH4 +-N), organic nitrogen, and total kjeldahl nitrogen removal efficiencies up to 98.2 ± 0.70%, 100%, and 99 ± 0.47%, respectively when COD of the influent and HLR were 200 ± 25mg/L and 3 ± 0.1 m3/m2-d, respectively. On the other hand, substantial enhancement in the nitrate nitrogen (NO3 --N) in the effluent (73 ± 10.55 times its influent concentration) was observed with influent COD of 200 ± 25mg/L and HLR of 7 ± 0.2 m3/m2-d. When the influent COD and HLR were maintained at 700 ± 45mg/L and 3 ± 0.1 m3/m2-d, respectively, the highest total nitrogen removal of 87 ± 2.25% was obtained. Alternatively, the influent COD of 200 ± 25mg/L and HLR of 3 ± 0.1 m3/m2-d yielded the highest COD removal efficiency of 77 ± 1.59%. Hence, the outcome of the present research work strengthens the suitability of the vermifiltration technology as an economically and ecologically sound natural wastewater bio-remediation technology for the treatment of domestic wastewater.

Treatment of slaughterhouse wastewater by electrocoagulation and electroflotation as a combined process: process optimization through response surface methodology.

The contamination of water with organic compounds has become an increasing concern in today's world. The cost-effective and sustainable treatment of industrial wastewaters is a major challenge. Advanced treatment techniques such as electrocoagulation-electroflotation offer economic and reliable solutions for the treatment of industrial wastewater. In this study, the electrocoagulation-electroflotation method was investigated for the simultaneous removal of chemical oxygen demand, total phosphorus, total Kjeldahl nitrogen, and color via response surface methodology. Factors such as electrode combination (Fe and Al), current density (10-20 mA/cm2), pH (3.0-9.0), and electrode distance (1-3 cm) were investigated in the treatment of wastewater to obtain maximum treatment efficiency. It was determined that chemical oxygen demand, total Kjeldahl nitrogen, total phosphorus, and color removal reached up to 94.0%, 77.5%, 97.0%, and 99.0%, respectively. Treatment costs were found as $0.71 with the Al-Fe electrode combination.

Bioelectrochemically assisted sustainable conversion of industrial organic wastewater and clean production of microalgal protein

Chlorella vulgaris, one of the single cell protein sources, is a promising alternative to address the ever-growing demand for food-quality protein. Efforts have been made to overcome the high production costs by using wastewater for the cultivation of C. vulgaris. However, direct use of wastewater poses threats to the safety of applying the obtained biomass for food and animal feed. This study applied a novel three-chamber microalgal-bio-electrochemical systems for simultaneous clean cultivation of C. vulgaris and treatment of industrial organic wastewater. Results demonstrated that the removal of COD (38.7–66.8%) and total Kjeldahl nitrogen (TKN, 49.8–69.0%) improved with the increase of electric current in both anode and cathode chambers. Meanwhile, comparable phosphorus removal rates of 34.2–48.5% were achieved in all operation modes. Through nutrients migration, the middle chamber recovered 34.4–39.4% TKN, 16.8–47.3% phosphorus, and acetate from the wastewater to support a mixotrophic growth of C. vulgaris. Moreover, increasing electric current promoted higher dry algal biomass weight (0.87–1.11 g L−1), higher protein content (320.8–552.1 mg Protein g−1 Biomass), and larger cell size (enlarged up to 151.2%) than the control. Nevertheless, the ratio of protein content decreased with the increase of cell size due to the prior accumulation of other compounds under mixotrophic growth. This study provides a sustainable approach for the conversion from industrial organic wastewater to clean production of microalgal protein.

Treatment of leachate through constructed wetlands using Typha angustifolia in combination with catalytic ozonation on Fe-zeolite A

Leachate control and management is a major challenge faced during solid waste management as it may pollute surface and groundwaters. In the current research, constructed wetlands (CWs) vegetated with Typha angustifolia plant in combination with catalytic ozonation by ferrous (Fe)-coated zeolite A was studied for the treatment of leachate. The CWs treatment with 9 days detention reduced the chemical oxygen demand (COD) and biochemical oxygen demand (BOD) up to 75.81% and 69.84%, respectively. Moreover, total suspended solids (TSS), total dissolved solids (TDS), and total kjeldahl nitrogen (TKN) removal of 91.16%, 33.33%, and 25.22% were achieved, respectively. The Fe-coated zeolite A catalytic ozonation further reduced the COD up to 90.7%. Comparison of the processes showed the effective performance of the combined process (CW/O3/Fe-zeolite) with 97.76% COD reduction of leachate. It is, therefore, concluded that the studied combined process (CW/O3/Fe-zeolite A) was more efficient as compared with single ozonation and CW alone, hence it can be implied for the leachate treatment in real conditions.