Total Kjeldahl Nitrogen Removal Efficiency Research Articles

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

AbstractThe 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

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.

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.

Proposal of upgrading Isfahan north wastewater treatment plant: An adsorption/bio-oxidation process with emphasis on excess sludge reduction and nutrient removal

There is a rising challenge in managing the activated sludge process due to excess sludge disposal from the wastewater treatment plant and inadequate effluent quality due to the stricter standard of effluent quality. Hence, the incorporation of oxic-settling-anoxic process and ultrasonic waves in the return sludge line was proposed to assess the excess sludge reduction and nutrient removal in the adsorption/bio-oxidation activated sludge process as a proposal upgrading. The results indicated that sludge production from adsorption/bio-oxidation process could be reduced using oxic-settling-anoxic and ultrasonic by 50% at each studied mixed liquor suspended solids level. Compared to the adsorption/bio-oxidation process, the total and soluble chemical oxygen demand removal efficiencies in adsorption/bio-oxidation process with oxic-settling-anoxic and ultrasonic slightly decreased suggesting a lysis phenomenon. During the operation of adsorption/bio-oxidation process with oxic-settling-anoxic and ultrasonic, the total Kjeldahl nitrogen removal efficiency improved in A and B stages, with 38.3 ± 8.1% and 83.1 ± 6.5% versus 36.8 ± 14.5% and 75.1 ± 7.3%, respectively. According to the stoichiometric calculations, in B stage of adsorption/bio-oxidation process with oxic-settling-anoxic and ultrasonic, the soluble available ultimate biochemical oxygen demand and net NO3 produced for denitrification were 69.5 and 43.8 mg/L, respectively. Overall, the experimental data revealed that the adsorption/bio-oxidation process with oxic-settling-anoxic and ultrasonic produced lower excess biological sludge and better total Kjeldahl nitrogen removal efficiency compared to the adsorption/bio-oxidation system alone.

Improved Wastewater Treatment by Combined System of Microbial Fuel Cell with Activated Carbon/TiO2 Cathode Catalyst and Membrane Bioreactor

A two-stage continuous process was developed for treating medium-strength wastewater combining microbial fuel cell (MFC) using activated carbon (AC)/TiO2 composite as cathode catalyst and submerged membrane bioreactor (MBR). Synthetic wastewater, having total chemical oxygen demand (COD) of around 3 g/L, was introduced first in the anodic chamber of MFC in a continuous mode of operation followed by aerobic MBR. Submerged hollow-fibre ultra-filtration membrane assembly was attached to draw permeate from MBR. The electrical performance of MFC was evaluated by polarisation, which showed a maximum volumetric power density of 1.02 W/m3 with much lower whole-cell internal resistance of 10 Ω. The coulombic efficiency of MFC was estimated to be 0.31%, demonstrating AC/TiO2 composite as a promising cathode catalyst for applications in MFC. The permeate of MFC–MBR system showed 98.3 ± 0.3% and 81.9 ± 1.8% of COD and total Kjeldahl nitrogen removal efficiency, respectively, producing permeate with total suspended solids concentration of less than 5 mg/L. Thus, a two-stage reliable process for treatment of wastewater is demonstrated using integrated MFC–MBR for generating high-quality recyclable effluent and facilitating recovery of bio-electricity.

TiO2/Activated carbon photo cathode catalyst exposed to ultraviolet radiation to enhance the efficacy of integrated microbial fuel cell-membrane bioreactor

Two integrated microbial fuel cell-membrane bioreactor (MFC-MBR) were developed to treat medium-strength wastewater with simultaneous power generation. Both the systems were operated with photo-sensitized cathode (with TiO2-Activated carbon) with one irradiated by UV-A light (MMT-UV), while the other was not in direct contact with any light sensitization (MMT). In polarization, MMT-UV exhibited higher maximum power density of 494 mW m−2 as compared to MMT (239 mW m−2). Normalized energy recovery was also estimated to be 0.122 kWh m−3 for MMT-UV and 0.058 kWh m−3 for MMT. On the other hand, overall chemical oxygen demand and total Kjeldahl nitrogen removal efficiency were almost similar and high enough ( ̴ 95% and 86–90%, respectively) for these type of two-stage wastewater treatment systems with very less footprint. Hence, the integrated MFC-MBR with TiO2-Activated carbon as cathode-catalyst in presence of UV showed excellent treatability of wastewater with simultaneous bioelectricity generation to reduce the overall energy demand.

Performance of the first stage of the French system of vertical flow constructed wetlands with only two units in parallel: influence of pulse time and instantaneous hydraulic loading rate.

The technology of vertical flow constructed wetlands - French system for treating raw wastewater depends on several hydraulic factors, one of them being the duration of the pulse feeding and the resulting instantaneous hydraulic loading rate. This paper analyses two scenarios in the same system, the first of a faster feeding by pump and the second of a slower feeding by siphon, both with instantaneous hydraulic loading rate values lower than the literature recommendations. The system treated raw wastewater from a population equivalent of 100 p.e. in Brazil, and was comprised by only the first stage and two units in parallel. The shorter duration of feeding time and higher instantaneous hydraulic loading rate were associated with significantly higher chemical oxygen demand and total Kjeldahl nitrogen removal efficiencies, but with no significant differences in terms of biochemical oxygen demand (BOD) and suspended solids (SS). Oxygen concentrations and redox potential in the effluent were evaluated, together with the effluent flow rate profiles. The removal efficiencies were associated with the accumulation of solids in the upper part of the filter resulting from seven years of operation and to the operating hydraulic conditions, which are important elements in the performance of the system.

BİYOLOJİK ATIKSU ARITMA TESİSLERİNDE KARBON VE AZOT GİDERİM VERİMLERİNİN TAHMİNİ AMACIYLA YAPAY SİNİR AĞLARININ KULLANIMI

Although Activated Sludge Model No. 1 (ASM1) was used for modelling biological nitrogen removal processes, estimation of input parameters required to run this model necessitates complicated laboratory analyses. In this study, the performance of Backpropagation Artificial Neural Networks (BPANN), which requires considerably less numbers of input parameters, in predicting chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN), and total nitrogen (TN) removal efficiencies was tested. For this purpose, four activation functions were employed in BPANN. Results suggested that COD, TKN, and TN removal efficiencies in AO processes can be accurately estimated using BPANN, with the highest learning and prediction capacity when Sinc function is employed. The mean square errors (MSEs) with Sinc-BPANN were calculated as 2.50 × 10 -4 for COD removal efficiency, 4.15 × 10 -4 for TKN removal efficiency, and 2.65 × 10 -4 for TN removal efficiency. Therefore, the Sinc-BPANN is concluded to be an efficient tool for estimating nonlinear nature of COD, TKN, and TN removal efficiencies in AO processes using considerably less numbers of input parameters.

Swine Farm Wastewater Treatment by Constructed Wetland Planted with Vetiver Grass

This research investigated the pollutant removal efficiencies in swine farm wastewater with Vetiveria zizanioides (L.) Nash (Sri Lanka ecotype) in a surface flow constructed wetland (SFCW). The SFCW units were set up to 3 treatments at 10, 15 and 30 cm water levels to find the proper depth for vetiver grass in wastewater treatment. The water quality indicator such as pH, temperature (T), biochemical oxygen demand (BOD), chemical oxygen demand (COD), total kjeldahl nitrogen (TKN), total phosphorus (TP) and heavy metals (Cu, Fe, Pb, Zn) were analyzed and compared with terms of removal efficiency. The 30 cm water depth has a better removal efficiency of organic substance treatment (BOD and COD). The BOD, COD, TKN and TP removal efficiency had no statistically significant differences between the water depths. TP has the best removal efficiency with average 95.18-96.53%. The treatment of heavy metals such as Cu, Pb, Fe and Zn with vetiver grass in different water depths was showed no statistical significance since it can reduce only a small number of these metals. However, the results showed that the effluent from all the treatment units contained averages of BOD, COD, TKN and pH that followed Thailand’s swine wastewater quality standard.

A comparative study of an up-flow aerobic/anoxic sludge fixed film bioreactor and sequencing batch reactor with intermittent aeration in simultaneous nutrients (N, P) removal from synthetic wastewater.

The performance of two bench scale activated sludge reactors with two feeding regimes, continuous fed (an up-flow aerobic/anoxic sludge fixed film (UAASFF) bioreactor) and batch fed (sequencing batch reactor (SBR)) with intermittent aeration, were evaluated for simultaneous nutrients (N, P) removal. Three significant variables (retention/reaction time, chemical oxygen demand (COD): N (nitrogen): P (phosphorus) ratio and aeration time) were selected for modeling, analyzing, and optimizing the process. At high retention time (≥6 h), two bioreactors showed comparable removal efficiencies, but at lower hydraulic retention time, the UAASFF bioreactor showed a better performance with higher nutrient removal efficiency than the SBR. The experimental results indicated that the total Kjeldahl nitrogen removal efficiency in the UAASFF increased from 70.84% to 79.2% when compared to SBR. It was also found that the COD removal efficiencies of both processes were over 87%, and total nitrogen and total phosphorus removal efficiencies were 79.2% and 72.98% in UAASFF, and 71.2% and 68.9% in SBR, respectively.

Lactic Acid Production from Repeated-Batch and Simultaneous Saccharification and Fermentation of Cassava Starch Wastewater by Amylolytic Lactobacillus Plantarum MSUL 702

The present study is aimed at determining the performance of an amylolytic Lactobacillus plantarum MSUL 702 for lactic acid production from the repeated-batch and simultaneous saccharification and fermentation (SSF) of a synthetic cassava starch wastewater (SCW). An ability of the bacteria to treat the SCW in terms of chemical oxygen demand (COD) and total kjeldahl nitrogen (TKN) removal efficiencies was also investigated during the fermentation processes. The SSF experiments were performed for five consecutive batches under a non-sterile condition and at a room temperature. The highest lactic acid concentration and viable lactic acid bacteria at 28.71g/L and 9.26 log CFU/mL, respectively, were obtained in the 48h of the first batch fermentation. The highest COD and TKN removal efficiencies at 98% and 85%, respectively, were obtained in the 48h of the second batch fermentation. The bacteria could retain the high lactic acid production and treatment efficiency up to four consecutive batches.

Application of sediment microbial fuel cell for in situ reclamation of aquaculture pond water quality

Performance of sediment microbial fuel cell (SMFC) with external resistance (SMFC-1) as well as short-circuited mode (SMFC-2) was evaluated at different operating temperatures (28–30°C and 21–25°C) and in presence and absence of aeration at the cathode. The performance was evaluated in terms of chemical oxygen demand (COD) removal and total kjeldahl nitrogen (TKN) removal for offering in situ treatment of aquaculture pond water. SMFC-2 demonstrated maximum COD and TKN removal efficiencies both in the absence and presence of aeration near cathode as compared to SMFC-1. With aeration at cathode, the COD and TKN removal efficiencies were 79.4% and 92.6% in SMFC-1 and 84.4% and 95.3% in SMFC-2, respectively. Without aeration and at lower operating temperature, the COD and TKN removals were slightly lower, yet satisfying aquaculture quality norms. SMFCs demonstrated effective in situ remediation of aquaculture water and can drastically save the operating cost of aquaculture.

Performance of 14 full-scale sewage treatment plants: Comparison between four aerobic technologies regarding effluent quality, sludge production and energy consumption

The performance of 14 Full-Scale Sewage Treatment Plants (STPs) was evaluated. STPs were divided into four aerobic technologies: a) Aerated Lagoon (AL), and three configurations of activated sludge technologies, b) conventional (CAS), c) Extended Aeration (EA), d) Sequencing Batch Reactor (SBR). Comparison between these configurations were made regarding: a) control parameters, organic loading rate (OLR), Mixed Liquor Volatile Suspended Solids (MLVSS) concentrations, Food to Microorganism ratio (F/M), sludge age (θc), Hydraulic Retention Time (HRT) and return sludge ratio (R); b) effluent quality, through 5-day Biological Oxygen Demand (BOD5), Chemical Oxygen Demand (COD), Total Suspended Solids (TSS), Total Kjeldahl Nitrogen (TKN), Total Phosphorus (TP); and c) indicators related to sludge production (on a dry basis) and electrical energy consumption. Also, complementary costs analyses were made. The results show that in terms of effluent quality, for all configurations organic matter (BOD5 and COD) and TKN removal efficiency were up to 90%, while TSS and TP were up to 90% and 50%, respectively. However, CAS, EA, SBR, and AL had stability problems with effluent concentrations. The results of the electrical energy consumption and sludge production analyses show that SBRs reduce these indicators by 40%. Cost analysis showed that CAS, EA, SBR and AL had similar cost structures, with more than 50% of total operating and maintenance cost being related to electrical energy and sludge management. Therefore, SBR could be defined as the configuration with a more stable performance.

Biodegradability Assessment and Treatability of High Strength Complex Industrial Park Wastewater

AbstractIndustrial park wastewater (IPWW) includes complex non‐biodegradable organic compounds. A wastewater treatability study using biodegradability assessment approach was carried out for an industrial park housing mainly textile and machinery sectors. Biodegradable and inert chemical oxygen demand (COD) fractions with soluble and particulate counterparts were experimentally estimated by implementing respirometric methods. Aerobic batch test methods and oxygen uptake rate profiles were used to map kinetic parameters and COD fractions. Denitrification potential was also determined by application of anoxic batch tests. Relevant kinetic constants, stoichiometric, and design parameters were determined for biological processes. Tests were carried out for raw and physico‐chemically pre‐treated IPWW. Hence, it was aimed to assess the effects and necessity of pre‐treatment on biological processes. Biological mineralization, nitrification, and denitrification processes were also designed and tested using a bench scale continuous treatment model for pre‐treated IPWW. The sum of initial inert soluble COD fraction and production of soluble microbial products decreased about 25% for the case of pre‐treated IPWW as compared to raw IPWW. Eighty‐three percent total COD and 89% total Kjeldahl nitrogen removal efficiencies were attained for the modeling experiments of pre‐treated IPWW. Results showed the significance of pre‐treatment if complex strength industrial wastewaters are to be biologically treated.

Performance of membrane bioreactor to different hydraulic shock loadings

A Membrane Bioreactor (MBR) treating simulated sewage was operated and stabilised for a period of 60 days at an organic loading rate of 3.6 g/COD/day and Hydraulic Retention Time (HRT) of 8 h, during which the MBR showed 95% removal of Chemical Oxygen Demand (COD), 98% removal of Total Organic Carbon (TOC) and TSS, 91% removal of Total Kjeldahl Nitrogen (TKN) and 30% removal of phosphate. The responses of the MBR to different hydraulic shock loadings were studied. The HRT was reduced to 4 h, 2 h, 1 h and 0.8 h to simulate two, four, eight and tenfold increase in flow rate, respectively, for a period of 12 h. During the shock load the influent COD concentration was maintained constant. Under the hydraulic shocks, the COD removal efficiency temporarily reduced to between 92% and 81% and the TOC removal efficiency reduced to between 80% and 48%. TOC removal efficiency was very poor at tenfold hydraulic shock. The TKN and phosphate removal efficiency were slightly affected at twofold hydraulic shock, showing a removal efficiency of 76% and 24%, respectively. The nitrogen and phosphate removal was highly affected at higher shock loads with very high TKN and phosphate concentration in the effluent. The system took much longer time (around 7 to 14 days) to recover in terms of nutrient removal for higher shock loads. The biomass was not at all affected at two, four and eightfold increase in flow rate. The high biomass and sludge retention of the MBR is advantageous to withstand such high and sudden hydraulic shocks, with its ability to recover faster than any other biological reactor.

Pós-tratamento de efluente nitrificado da parboilização de arroz utilizando desnitrificação em reator UASB

Um sistema combinado reator UASB-reator aeróbio foi utilizado para a remoção de nitrogênio total e DQO de efluente de parboilização de arroz. O experimento foi realizado em reatores de bancada, com volumes de 4 L (UASB) e 3,6 L (reator aeróbio). Os parâmetros de operação pH, temperatura, alcalinidade e concentração de ácidos voláteis foram monitorados durante o período experimental. Para o reator aeróbio de mistura completa, foi determinada, também, a concentração de oxigênio dissolvido. O sistema combinado reator UASB-reator aeróbio apresentou uma eficiência de remoção de carbono de 84% e uma eficiência de remoção de nitrogênio total Kjeldahl de 83%. O sistema proposto, nas condições experimentais, demonstrou ser adequado para remoção, simultânea, de DQO e de compostos oxidados de nitrogênio, em reator UASB.

Landfill Leachate Treatment by Yeast and Bacteria Based Membrane Bioreactors

Biological treatment of medium-age landfill leachate was investigated on a membrane bioreactor. The experiments were conducted in two 5-L reactors with immersed hollow fiber microfiltration membranes. One reactor was operated with a mixed bacterial culture termed as bacteria based membrane bioreactor (BMBR) while the other with mixed yeast culture termed as yeast based membrane bioreactor (YMBR). The leachate was characterized with a chemical oxygen demand (COD) concentration of 7000–9000 mg/L, biochemical oxygen demand (5 days) to chemical oxygen demand ratio (BOD5/COD) of 0.35–0.45 and total Kjeldahl nitrogen (TKN) of 1800–2000 mg/L. The performance was assessed with and without ammonia stripping. In both the reactors, the average COD and TKN removal efficiency without ammonia stripping ranged between 52–66 and 14–28%, respectively. The performance of both the membrane bioreactors improved with ammonia stripping in terms of both COD (72–76%) and TKN (82–89%) removal efficiency. Though, the difference in the performance of the BMBR and YMBR was not significant in terms of COD removal, the YMBR showed better removal efficiency in terms of BOD5. The molecular weight cut-off showed that the degradation pathway of the leachate by bacterial and yeast are different. In regard to membrane fouling, the YMBR showed better performance with lower trans-membrane pressure as well as longer operating time. This superior performance of the YMBR could be due to the structure of yeast cells which are larger in size as well as reduced soluble extracellular polymeric substances (EPS) production, which are the main cause of membrane biofouling.

Landfill Leachate Treatment by Yeast and Bacteria Based Membrane Bioreactors

Abstract Biological treatment of medium-age landfill leachate was investigated on a membrane bioreactor. The experiments were conducted in two 5-L reactors with immersed hollow fiber microfiltration membranes. One reactor was operated with a mixed bacterial culture termed as bacteria based membrane bioreactor (BMBR) while the other with mixed yeast culture termed as yeast based membrane bioreactor (YMBR). The leachate was characterized with a chemical oxygen demand (COD) concentration of 7000–9000 mg/L, biochemical oxygen demand (5 days) to chemical oxygen demand ratio (BOD5/COD) of 0.35–0.45 and total Kjeldahl nitrogen (TKN) of 1800–2000 mg/L. The performance was assessed with and without ammonia stripping. In both the reactors, the average COD and TKN removal efficiency without ammonia stripping ranged between 52–66 and 14–28%, respectively. The performance of both the membrane bioreactors improved with ammonia stripping in terms of both COD (72–76%) and TKN (82–89%) removal efficiency. Though, the difference in the performance of the BMBR and YMBR was not significant in terms of COD removal, the YMBR showed better removal efficiency in terms of BOD5. The molecular weight cut-off showed that the degradation pathway of the leachate by bacterial and yeast are different. In regard to membrane fouling, the YMBR showed better performance with lower trans-membrane pressure as well as longer operating time. This superior performance of the YMBR could be due to the structure of yeast cells which are larger in size as well as reduced soluble extracellular polymeric substances (EPS) production, which are the main cause of membrane biofouling.