NH3-N Removal Research Articles

Sustainable leachate pre-treatment using microbial desalination cell for simultaneous desalination and energy recovery

Leachate treatment technologies struggle with low treatment efficiencies due to complex and toxic chemicals in leachate. Therefore, mixing leachate with low-density wastewater could be beneficial. This research studied the feasibility of pretreating a mixture of leachate and municipal wastewater (1:4) in a microbial desalination cell (MDC) for the first time. The study examined the MDC potential in removing organics and NH3-N from leachate-wastewater mixture along with measuring the desalination efficiency and energy recovery at different applied external resistance (Rext). The results showed that MDC-1 (at Rext = 1 Ω) showed a higher desalination rate (DR) (35.71 mg/h) and higher NH3-N removal (36%) with lower COD removal (28%) compared to MDC-100 (at Rext = 100 Ω) with DR = 17.98 mg/h, NH3-N removal of 10% and COD removal of 78.26%. The results revealed that Rext could regulate the pollutants (organics, NH3-N) removal and desalination efficiency. The lack of soluble organics could also result in significant discrepancies in bioelectrochemical performance. MDC-100 showed four times higher energy output (5.63 W·m−3) compared to MDC-1 (1.39 W·m−3), while MDC-1 showed five times higher columbic efficiency (29.3%) compared to MDC-100 (5.52%). Future studies should investigate the best MDC configurations for the optimum leachate-wastewater ratio for sustainable leachate treatment.

COD/TN ratios shift the microbial community assembly of a pilot-scale shortcut nitrification-denitrification process for biogas slurry treatment.

In this study, effects of carbon to nitrogen (COD/TN) ratios of biogas slurry on shortcut nitrification-denitrification in a pilot-scale integrated fixed film activated sludge (IFAS) system were investigated. Lowering the COD/TN ratio from 11.7 to 6.2 exerted a negative impact on shortcut nitrification-denitrification performance. Accordingly, the NH3-N and TN removal rates decreased from 94.4 to 91.2% and 92.3 to 85.9%, respectively. The dynamics of microbial assembly was analyzed by MiSeq sequencing, and the denitrifying functional genes were quantified by qPCR. The results showed that ammonia oxidizing bacteria and amoA gene were more abundant on the biofilm of oxic tank, indicating they play a key role in NH3-N removal. Autotrophic, endogenous, and fast heterotrophic kinetics denitrifiers were coexisted and enriched in the IFAS system with a decreasing of COD/TN ratio. TN removal was mainly affected by denitrifiers (including Arenimonas, Acidovorax, and Thaurea) harboring narG and nirS genes. Canonical correspondence analysis proved that COD/TN ratio was the most critical factor driving the succession of microbial community. Dissolved oxygen (DO) and pH were found positively correlated with denitrifiers at low COD/TN ratio conditions. As a result, NH3-N and TN removal were effectively enhanced when the DO level in the oxic tank of IFAS system was increased to 1.0-3.0 mg/L.

Removal of COD, TDS and Ammonia (NH3-N) in Produced Water with Electrochemical Using Aluminum (Al) and Iron (Fe) Electrode

The activities of the oil and gas industry have the potential to cause pollution for the environment. This pollution can arise due to the production of petroleum processing, storage, and industries that use petroleum. Produced water is the largest liquid waste generated by these activities. The number will increase as long as a field where exploration continues to produce. In this study, an electrochemical method using Al-Fe electrodes with the addition of 1 g/L NaCl as an agent to provide chlorine as an oxidation mediator to accelerate NH3-N removal in produced water. Chemical reactions that occur during the electrochemical process as driving force, the reduction process is specific with conductive and active electrochemical substances then can manipulated with potential (voltage) and current time. A combination of an electrode is using aluminum and iron electrode plates with each thickness 0.1mm. The voltage variations during the process were 3, 6, 9, and 12V. This process is continuous, and samples are taken every 45, 90, 135, 180, and 225 minutes. The results showed percentage of COD removal is 53.14% from 430.25 mg/L to 201.6 mg/L, ammonia (NH3-N) removal is 91.64% from 17.71 mg/ L to 1,48 mg/L and TDS removal is 78.14% from 12670 mg/L to 2769 mg/L. 9V for 225 minutes during the electrochemical process is an optimum condition that can reduce contaminants in produced water, so the quality standards of Minister of Environment Regulation No.19 2010 are fulfilled. The electrochemical method was chosen to produce water treatment because the equipment required is simple and easy to operate and does not cause new waste.

Long-term investigations on ammonium removal with zeolite in compact vertical flow treatment wetlands under field conditions.

The scope of this study was to investigate if using zeolite as a reactive material in a vertical-flow wetland under field conditions improves ammonium removal from domestic wastewater in the long term. The experimental setup consisted of two pilot-scale first stage French vertical flow treatment wetlands (2.3 m2 surface area each), which were implemented under field scale conditions inside a wastewater treatment plant in the central region of France (L'Encloitre, 37360). The filters were operated during 27 months. A compact pilot containing Leca® as a main filtration layer (Ø 1-5 mm) was compared to a similar one filled with natural zeolite (Ø 2-5 mm). The pilots were fed according to regular feeding/resting periods (3½/7 days) and the nominal loading rate was of 300 g COD m-2 d-1 and 33 g·N·m-2·d-1 during operation. In both pilots, results showed a removal efficiency of more than 90 and 85% for TSS and COD, respectively. They also showed an increased NH4-N removal of 9% on average (total removal efficiency of 84%) with the use of zeolite compared to Leca®. The ion exchange capacity of zeolite seemed not to be affected after 27 months of experiments; however, the material was compacted and more friable after operation.

Synergistic adsorption and photocatalytic properties of AC/TiO2/CeO2 composite for phenol and ammonia–nitrogen compound degradations from petroleum refinery wastewater

This study focuses on the utilization of AC/TiO2/CeO2 composite on the removals of phenol and ammonia–nitrogen (NH3-N) compounds from petroleum refinery wastewater (PRW) through a combination of adsorption and photocatalytic process. The composite was prepared by hydrothermal method with the composite formulation of 53.43%-wt of AC, 21.96 %-wt of TiO2, and 24.61 %-wt of CeO2. Characterization results revealed that the surface micromorphology, elemental, and oxide contents on synthesized composite significantly changed with the addition of TiO2 and CeO2. Optical UV–vis analysis showed that the estimated bandgap energy of the synthesized composite was 2.60 eV, which is lower than pristine TiO2 or CeO2, indicating that the photocatalysis is easier to perform that reflecting the successful combination of TiO2 and CeO2 as the photocatalyst in the composite. The Langmuir isotherm and pseudo-second order kinetic showed to be the most favorable isotherm and kinetic model for the adsorption process. The photocatalytic activity and kinetic evaluations showed that the photocatalytic process remarkably improved the removal performance and was followed the pseudo-first order kinetic. Moreover, the rate constants of photocatalysis were higher than the adsorption process, indicating that the rate of photocatalysis on the pollutant degradations is faster than the adsorption process. The final pollutant removals by using AC/TiO2/CeO2 composite were 50.91% for phenol removal and 65.83% for NH3-N removal. Three consecutive cycles test showed that the AC/TiO2/CeO2 composite has excellent durability and can nicely maintain the phenol and NH3-N removals from PRW.

Treatment of coking wastewater in a heterogeneous electro-Fenton system: Optimization of treatment parameters, characterization, and removal mechanism

Coking wastewater is a typical refractory industrial wastewater with complex hazardous materials and high organic content. A novel heterogeneous electro-Fenton system with a homemade iron-loaded activated carbon cathode was used to treat coking wastewater. Based on response surface methodology, chemical oxygen demand (COD) and ammonia nitrogen (NH3-N) were used as research indicators for the optimization of the reaction parameters. Under the optimal conditions of 1 cm electrode spacing, 10 V applied voltage, and initial pH of 3.88, the COD removal rate in several experiments was 88.91–96.65%, and the NH3-N removal rate in several experimental runs was up to 100%. We used ultraviolet-visible spectroscopy, Fourier-transform infrared spectroscopy, three-dimensional excitation-emission matrix fluorescence, gas chromatography–mass spectrometry, and color analysis for analyses; and found that the cyclic aromatic compounds and hazardous materials containing unsaturated double and triple bonds could be effectively degraded by the modified electro-Fenton method. Additionally, the color of the coking wastewater can also be effectively removed using this technique. The studied mechanisms and UV254 analysis illustrated that the modified electro-Fenton method can effectively degrade COD and NH3-N, remove most hazardous materials, and improve the biodegradability of coking wastewater.

Evaluation of various preparation methods of oil palm fiber (OPF) biochar for ammonia-nitrogen (NH3-N) removal

The aim of this study is to develop a oil palm based biochar for the selective removal of NH3-N in low concentration from aquaculture wastewater. In this study, three different preparation methods of biochar were evaluated for the adsorption of NH3-N from synthetic aquaculture wastewater. The three methods are pyrolysis, activation with acid before pyrolysis and activation after pyrolysis with numerous oxidizing agents. In the 1st method, various biochars have been prepared at different pyrolysis temperatures (300 – 500 °C) and holding time (0.5 – 2 hr). The maximum removal efficiency of 50 % was achieved at preparation condition of 300 °C and 2 hr. In the 2nd method, the acid activated raw OPF was pyrolyze at 300 °C, 1 hr. The maximum removal was lower compared to the 1st method without acid treatment. In the 3rd Method, the optimized biochar from the 1st method was activated with different activating agents such as, HNO3, HCl, H3PO4, H2SO4, CH3COOH and H2O2 at 100 °C for 2 hr. It was noticed that activation after pyrolysis did not show any improvement in the removal of NH3-N from synthetic aquaculture wastewater. Characterization of optimized samples were carried out to investigate the adsorption mechanism process of NH3-N. The 1st method (pyrolysis) was the best which reported the highest (50 %) removal of NH3-N. Pyrolyzed OPF is a potential adsorbent for NH3-N.

Environmental Remediation Potential of Ferrous Sulfate Waste as an Eco-Friendly Coagulant for the Removal of NH3-N and COD from the Rubber Processing Effluent

The present study was conducted to determine the potential of utilizing the FeSO4·7H2O waste from the titanium manufacturing industry as an effective coagulant for treating industrial effluent. In this study, the secondary rubber processing effluent (SRPE) was treated using ferrous sulfate (FeSO4·7H2O) waste from the titanium oxide manufacturing industry. The FeSO4·7H2O waste coagulation efficiency was evaluated on the elimination of ammoniacal nitrogen (NH3-N) and chemical oxygen demand (COD) from SRPE. The central composite design (CCD) of experiments was employed to design the coagulation experiments with varying coagulation time, coagulant doses, and temperature. The coagulation experiments were optimized on the optimal elimination of NH3-N and COD using response surface methodology (RSM). Results showed that coagulant doses and temperature significantly influenced NH3-N and COD elimination from SRPE. The highest NH3-N and COD removal obtained were 98.19% and 93.86%, respectively, at the optimized coagulation experimental conditions of coagulation time 70 min, coagulant doses 900 mg/L, and temperature 62 °C. The residual NH3-N and COD in treated SPRE were found below the specified industrial effluent discharge limits set by DoE, Malaysia. Additionally, the sludge generated after coagulation of SRPE contains essential plant nutrients. The present study’s finding showed that FeSO4·7H2O waste generated as an industrial byproduct in a titanium oxide manufacturing industry could be utilized as an eco-friendly coagulant in treating industrial effluent.

Optimization and Modeling of Ammonia Nitrogen Removal from High Strength Synthetic Wastewater Using Vacuum Thermal Stripping

Waste streams with high ammonia nitrogen (NH3-N) concentrations are very commonly produced due to human intervention and often end up in waterbodies with effluent discharge. The removal of NH3-N from wastewater is therefore of utmost importance to alleviate water quality issues including eutrophication and fouling. In the present study, vacuum thermal stripping of NH3-N from high strength synthetic wastewater was conducted using a rotary evaporator and the process was optimized and modeled using response surface methodology (RSM) and RSM–artificial neural network (ANN) approaches. RSM was first employed to evaluate the process performance using three independent variables, namely pH, temperature (°C) and stripping time (min), and the optimal conditions for NH3-N removal (response) were determined. Later, the obtained data from the designed experiments of RSM were used to train the ANN for predicting the responses. NH3-N removal was found to be 97.84 ± 1.86% under the optimal conditions (pH: 9.6, temperature: 65.5 °C, and stripping time: 59.6 min) and was in good agreement with the values predicted by RSM and RSM–ANN models. A statistical comparison between the models revealed the better predictability of RSM–ANN than that of the RSM. To the best of our knowledge, this is the first attempt comparing the RSM and RSM–ANN in vacuum thermal stripping of NH3-N from wastewater. The findings of this study can therefore be useful in designing and carrying out the vacuum thermal stripping process for efficient removal of NH3-N from wastewater under different operating conditions.

Deployment and Optimisation of a Pilot-Scale IASBR System for Treatment of Dairy Processing Wastewater

Increased pressure is being applied to industrial wastewater treatment facilities to adhere to more stringent regulations for the discharge of treated wastewater and to improve energy efficiency of the process. Nitrogen and phosphorous removal can be challenging to achieve efficiently, and in the case of phosphorous removal, can often necessitate the use of chemicals. There is a major drive globally to improve wastewater treatment infrastructure, whilst simultaneously reducing the carbon footprint of the process. The intermittently aerated sequencing batch reactor offers a modification of the well-known sequencing batch reactor process that can enable lower energy requirements than conventional sequencing batch reactor processes and can facilitate enhanced nutrient removal capacities. However, to date much of the previous literature has focused on relatively short laboratory-scale trials (often with synthetic wastewater) which may not be representative of larger scale system performance. This study explored the intermittently aerated sequencing batch reactor technology via a case-study deployment at a dairy production facility, in terms of treatment efficiency and energy efficiency with a focus on optimisation between phases. High treatment capacity and operational flexibility was achieved with NH4-N removals averaging >89%, PO4-P removal averaging >90% and total suspended solids removal averaging >97%. This research demonstrates the characteristics of intermittently aerated sequencing batch reactor technology at scale to effectively achieve biological nutrient removal. In addition, this study demonstrated that when effectively managed, energy savings and reductions in carbon emissions in the region of 36–68% are achievable through optimisation of reactor operation.

Performance of combined persulfate and tannin for the treatment of anaerobically treated palm oil mill effluent

<p>The current research was aimed to investigate the performance of combined persulfate oxidation process and tannin via coagulation-flocculation processes as a post treatment of anaerobically treated palm oil mill effluent (AnT-POME). Different dosages of sodium persulfate (Na2S2O8, 238 g/mol) 0.1 (w/v) and modified tannin were combined as a simultaneous reaction to treat AnT-POME. Different dosages of tannin ranged between 0.02g and 0.12g with pH variation ranged between 3 and 11 retention and retention time of (30, 90, 120 and 180) were evaluated. The performance of the treatment processes was evaluated based on the removal of three different parameters namely; chemical oxygen demand (COD), ammoniacal nitrogen (NH3-N) and color under the following operational conditions: persulfate dosage, tannin dosage, pH and retention time (min). Using persulfate alone, the maximum removal efficiency of COD, color, and NH3-N were 50%, 60% and 22%, respectively by using 4 mL of 0.1 (w/v) persulfate dosage at pH 7 and 60 min retention time. While, the performance of simultaneous reaction improve the removal efficiencies of COD, color, and NH3-N to 90%, 96% and 44%, respectively using 4 mL of 0.1 (w/v) persulfate and 0.06 g of tannin during 120 min retention time at pH 7. However, the maximum removal of NH3-N (59%) was achieved at pH 11. The study revealed that the simultaneous persulfate/tannin reaction is a promising treatment method for industrial wastewater treatment.</p>

Treatment of domestic sewage and leachate using a moving bed hybrid bioreactor

The treatment of domestic sewage using a moving bed hybrid bioreactor (MBHBR) was investigated by varying the concentrations of chemical oxygen demand (COD) (156 ± 14-1141 ± 78 mg/L), ammonia (NH3-N) (2 ± 0.08-48.24 ± 0.93 mg/L), phosphorus (PO4-P) (97 ± 3.2-281 ± 2.65 mg/L), and hydraulic retention times (HRTs). Initially, the reactor was operated at start-up mode (COD: 156 ± 14 mg/L), and gradually the COD concentrations were increased from phase-I (257 ± 24 mg/L) to phase-V (1141 ± 78 mg/L) by reducing the HRTs from 48 to 3 h. A significant improvement in COD removal, maximum up to 96%, was observed at a concentration of 858 ± 51 mg/L (phase-IV), then a sudden drop up to 81% was observed at a higher concentration of 1141 ± 78 mg/L (phase-V). Due to the increase in COD concentrations, average NH3-N removal was dropped from 85 to 32% from phase-I to Phase-V, respectively. In addition, the stability of MBHBR was studied to understand its performance in shut-down and shock loading phases. The co-treatment of sewage and leachate was also performed in MBHBR (COD: 864-881 mg/L and HRT: 6 h), which showed a COD removal of 77%–80% and NH3-N removal of 60%–94%. Proteobacteria was identified as a predominant species in MBHBR, which played a significant role in the co-treatment of sewage and leachate. The maximum biodegradation rate (rmax) and half-saturation constant (Ks) were estimated as 13.3 mg/L h and 361.8 mg/L, respectively.

A review on the application of nanoporous zeolite for sanitary landfill leachate treatment.

This review deals with low-cost nanoporous zeolites for the treatment of sanitary landfill leachate. Organic contaminants and ammoniacal nitrogen are significant parameters in landfill leachate treatment. Adsorption processes are regarded as promising alternative treatment options in this respect. Zeolites are aluminosilicate materials that are widely used in separation, filtration, adsorption and catalysis. Natural zeolite is a low-cost and readily available form of zeolite and is a promising candidate to be used as an ion-exchange material for ammonia and other inorganic pollutant removal from landfill leachate. In this review, adsorption isotherms and kinetic models in batch systems are evaluated and adsorption design parameters of the fixed-bed system are presented. Studies on ammonia removal from landfill leachate via zeolites have been thoroughly investigated. Leachate treatment systems combined with zeolites are presented. Cost of zeolites are also reported in comparison with other adsorbents. The investigated studies demonstrate that activated zeolite can improve the removal of chemical oxygen demand, NH3-N and colour significantly compared to the case where raw zeolite is used. Moreover, the composite of activated carbon and zeolite is also favorable for ammonia removal according to reported findings, where best adsorptive removal is attained on the composite media (24.39 mg/g).

The treatment of high-concentration garlic processing wastewater by UASB-SBR

ABSTRACT The treatment of garlic processing wastewater was investigated in a UASB-SBR system. The experimental results showed that UASB was successfully started up after 64 days of continuous operation with COD removal rate of 45%. SBR start-up phase went through 60 days and the COD removal rate achieved 96%. UASB ran under optimal conditions (HRT of 45 h, pH of 7.5, and temperature of 35 ± 2°C) for 14d and performed well in organic matter treatment. SBR played a major part in nitrogen and phosphorus removal when running under optimal conditions (cycle time of 12 h, temperature of 25°C, organic loading of 0.72 kgCOD/(m3·d), and COD of 6000 mg/L) for 18d. Secondly, the microbial community structure indicated that the abundance of β-Proteobacteria and α-Proteobacteria in the sludge reached 30.05% and 47.57%, respectively, and played a crucial part for the organic matter, nitrogen and phosphorus removal in the SBR. After UASB-SBR system had been stabilised with influent COD of 9800 mg/L, the average COD, TP, NH3-N and TN removal rates were 99%, 94.82%, 87.07% and 94.87%, respectively, which were 3%, −2%, 1% and 3.5% higher than SBR running alone under optimal conditions. UASB coupled with SBR process had an excellent performance for high-concentration garlic processing wastewater.

Optimization of AC/TiO2/CeO2 composite formulation for petroleum refinery wastewater treatment via simultaneous adsorption-photocatalytic process using D-optimal mixture experimental design

This study aims to optimize the formulation of activated carbon/titanium oxide/cerium oxide (AC/TiO2/CeO2) composite for petroleum refinery wastewater (PRW) treatment via simultaneous adsorption and photocatalytic process. D-optimal mixture experimental design was applied to predict the optimal formulation of the composite. The experimental data were assessed to generate empirical models for analyzing the effects of components fraction on individual responses. The fitted models were statistically examined (through the standard error of design), considerably validated (via analysis of variance (ANOVA) and model adequacy indicators), and experimentally verified (by estimating errors, root-mean square error (RMSE), and standard error of prediction (SEP) between the predicted and actual values). Finally, the optimized formulation was accepted to have 36.85% total dissolved solid (TDS) removal, 49.23% chemical oxygen demand (COD) removal, treated PRW with pH = 7.22 and electrical conductivity (EC) = 2937.11 µS/cm, 53.76% phenol removal, and 52.86% NH3-N removal, by applying 53.43%-wt of AC, 21.96%-wt of TiO2, and 24.61%-wt of CeO2 with reasonably high desirability score of 0.8874. Based on the characterization results, it can be concluded that the optimized AC/TiO2/CeO2 composite was successfully synthesized. From the diffuse reflectance spectrometry (DRS), the estimated bandgap energy of the synthesized AC/TiO2/CeO2 composite was successfully reduced through the use of CeO2. Our findings show the efficiency, reliability, and feasibility of the D-optimal mixture experimental design from modeling, predicting, and optimizing the formulation of AC/TiO2/CeO2 composite. Overall, our findings prove that the optimized AC/TiO2/CeO2 composite is a prominent and effective material for PRW treatment.

Pilot study on the treatment of lake water with algae by ultrafiltration–ozone–biologically activated carbon

Abstract For the treatment of lake water with algae, the coagulation–ultrafiltration–ozone–biologically activated carbon (CUF–O3–BAC) integrated process was first used to treat East Taihu Lake water in China, aiming at evaluating the removal efficiencies of algae, permanganate index (CODMn), UV254, NH3-N and disinfection by-products (DBPs) precursors. In addition, the long-term performance of the membrane operation under the fluxes of 60, 70, 80 and 90 L/(m2·h) was also investigated, and kinetic models were established. The experimental results showed that the integrated process had positive impaction of algae, CODMn, UV254 and NH3-N removal, and the removal rates were 95.89 ± 1.52, 76.18 ± 4.38, 72.06 ± 4.72 and 81.31 ± 6.71%, respectively. The CUF process was prone to increase the formation potentials of DBPs. Although ozone could reduce the formation risks of chlorinated trihalomethanes (THMs) to a certain extent, it is ineffective to reduce those of brominated THMs and haloacetic acids (HAA5). However, the CUF–O3–BAC process was an effective technology for the removal of THMs and HAA5 precursors in drinking water treatment. Finally, it was found that the relationship between transmembrane pressure (TMP) and time conformed to the first-order and second-order kinetic models, and the linear fitting coefficients were all above 90%.

Simultaneous desalination and ammonia recovery using microbial electrolysis desalination and chemical-production cell: A feasibility study of alkaline soil washing wastewater

The high concentrations of ions and ammonia nitrogen (NH3−N) in soil washing wastewater can remarkably affect ecosystem balance. This study aims to prove the feasibility of using alkaline soil washing wastewater as inlet water of microbial electrolysis desalination and chemical-production cell (MEDCC) to desalinate and recover NH3-N, from the views of performance and mechanism. The system could obtain desalination, and NH3-N removal efficiencies of 73 ± 7% and 85 ± 3%, respectively, within 12 h at the maximum current density of 9.8 ± 0.1 A/m2. Importantly, 82.5% of the removed NH3-N could be recovered in the form of NH3·H2O. The addition of electrochemically active bacteria in the anode chamber of MEDCC improved desalination and NH3-N recovery efficiencies by strengthing electric field. Bioenergy provided 58% of the total energy consumption, forming an energy-saving method for soil washing wastewater treatment. Alkalization pretreatment and acid immersion could reduce precipitation from membranes to improve desalination performance and reduce energy consumption. From the standpoint of the mechanism of desalination and NH3-N recovery, the MEDCC is expected to have the potential to simultaneously complete desalination and NH3-N recovery in alkaline wastewater with low energy consumption.

Spatial Pattern of Dissolved Nitrogen in the Water on Receiving Agricultural Drainage in the Sanhuanpao Wetland in China

The total nitrogen (TN) increases and the water quality deteriorates when a large amount of nitrogen-containing water is discharged from farmlands into wetlands. This research on the relationship between the TN, ammonia nitrogen (NH4-N), and nitrate nitrogen (NO3-N) concentrations in water has a certain reference significance for understanding the spatial pattern of nitrogen removal in wetlands. Taking the Sanhuanpao wetland in northeast China as the research object, 24 sampling plots in the study area were sampled in the spring and summer of 2017 to test the concentrations of TN, NH4-N, and NO3-N. Based on the calculations of the change rates of the TN, NH4-N, and NO3-N in spring and summer, a step-by-step elimination analysis was carried out and the spatial pattern of the TN, NH4-N, and NO3-N removals were revealed by gradual buffer extrapolations, combined with stepwise fitting functions. The results show that the removal capacity of NH4-N is strong within the range of 14.55 km–20 km and 26.93 km–35.96 km from the wetland inlet, and the removal capacity of NO3-N is relatively strong within the range of 26.93 km–35.96 km. The strong NH4-N and NO3-N removal areas in the wetland are not in the geometric center of the wetland, but in separate narrow areas around the center. The TN removal along water channel direction is only 0.25 times higher than that direction perpendicular to the channel, indicating that regardless of whether wetlands are expanded along the water channel or perpendicular to the water channel, the difference to the TN removal is small. Effectively monitoring and managing the reception of agricultural drainage is extremely important for maintaining the water-purification function of wetlands. The aim of the research is to reveal a spatial law of nitrogen removal in wetland water, and provide a framework for studying the mechanism of spatial difference of nitrogen.

Comparisons of coagulation efficiency of conventional aluminium sulfate and enhanced composite aluminium sulfate/polydimethyldiallylammonium chloride coagulants coupled with rapid sand filtration

Conventional aluminium sulfate (AS) coagulant's inability to effectively meet stringent water quality requirements have created the need to explore enhanced composite coagulants. The coagulation efficiency of AS and composite AS and polydimethyldiallylammonium chloride (AS/PDMDAAC) coagulants were investigated using jar test and then, coupled with rapid sand filtration (RSF). The various composite AS/PDMDAAC at different intrinsic viscosity of PDMDAAC and mass ratio of PDMDAAC to AS in coagulant solutions were optimized and operated at same supernatant turbidity (SST) or same dosage mode (SD). The results showed about 7–10% reduction in dosage for all composite AS/PDMDAAC and also improved water qualities compared to AS only. The patterns of water quality improvements at lower (0.65 dL/g), medium (1.60 dL/g), and higher (2.60 dL/g) intrinsic viscosity of cationic polymer PDMDAAC among different mass ratio of PDMDAAC to AS in the composite mixtures were 5:1 > 20:1 > 10:1; 10:1 ≥ 5:1 > 20:1; 20:1 > 10:1 > 5:1 respectively. The percentage removal efficiencies for AS and optimal composite coagulant at intrinsic viscosity (1.60 dL/g) and mass ratio (10:1) operated at SST or SD after filtration for CODMn, NH3N and turbidity were (71.20, 72.72, 73.33%); (69.15, 69.23, 73.08%) and (93.89, 95.07, 97.26%) respectively. It was concluded that enhanced composite AS/PDMDAAC coagulants operated at SST mode showed significant water quality improvement than conventional AS having 7% and 31.8% for COD and NH3N removal while operational mode at SD produced more significant water quality improvements than conventional AS with 9.49%, 45.45%, and 39.55% for COD, NH3N, and turbidity removal before filtration respectively. More importantly, all composite AS/PDMDAAC met stringent water quality requirements before and after filtration. This research provided new insight about application of economical and effective alternative composite AS/PDMDAAC coagulant useful in the treatment of water for large population.

Preparation and performance evaluation of novel magnetic porous carriers in fluidized bed bioreactor for wastewater treatment.

Biofilm process is a promising wastewater treatment technology and biofilm carrier (biocarrier) is regarded as the core of this process. However, the traditional commercial biocarriers have their inherent drawbacks, therefore, the development of new-type biocarrier to enhance wastewater treatment efficiency is significantly important to biofilm-based reactors. In this study, based on radical suspension polymerization, a novel kind of magnetic porous carriers (PMCs) was prepared by modifying the porous polymer carriers (PPCs) with inorganic particles, and then applied in a fluidized bed bioreactor (FBBR) with a low packing ratio of 10 % (v/v) to synthetic wastewater treatment. The results showed that this novel biocarrier possesses paramagnetism with saturation magnetization of 1.01emu/g, low density (1.26g/cm3), excellent hydrophilicity (surface water contact angle approaching zero) and rough surface. Besides, compared with the PPCs, the developed PMCs have larger pores (up to 50μm or more), in which the larger-sized microbes are able to colonize. Moreover, as compared to the PPCs-based FBBR, the PMCs-based reactor achieved shorter time (7 days) for biofilm formaiton and significantly enhanced NH3-N removal efficiency ( nearly 20 % increase at the level of influent NH3-N concentration about 100mg/L). High-throughput sequencing (HTS) results indicated that this new biocarrier could promote biodiversity and improve the abundance of Nitrosomonadales (the functional bacteria for ammonia removal in the bio-system), thus enhancing the ammonification process. Therefore, the developed PMCs could be preferable biocarriers for biofilm formation and provide an alternative to the traditional suspended biocarrier, demonstrating a promising potential, even at a lower filling ratio, to enhance the pollutants removal performance.