Ammonium removal by modified zeolite from municipal wastewater

Ammonium removal by modified zeolite, H-form and Na-form zeolite, were examined by batch-type methods. The adsorption of ammonium on modified zeolite was exothermic process. The saturation adsorption capacity of ammonium on H-form and Na-form zeolite were 21.23 and 41.15 mg/g, respectively. After ten times adsorption-desorption-readsorption cycles the standard deviations of H-form and Na-form zeolite were 6.34% and 6.59%. The zeolite adsorption process has proved cost effective and practical in reducing ammonium by H-form and Na-form zeolite in municipal wastewater from concentration 27.68 mg/L to 2.80 mg/L and 5.91 mg/L.

Technical Innovation of Land Treatment Systems for Municipal Wastewater in Northeast China

On the basis of ecological principles including holistic optimization, cycling and regeneration, and regional differentiation, land treatment systems (LTSs) for municipal wastewater were continuously explored and updated in the western Shenyang area and the Huolinhe area, China. Intensified pretreatment, addition of a man-made soil filtration layer, and use of an ecologically diversified secondary plant cover were proved to be technically feasible. Hydraulic loading was determined according to the assimilation capacity of soil ecosystems, thus ensuring safe operation of wastewater treatment. This modernized and alternative approach to wastewater treatment had been widely applied in middle-sized and small cities and towns of Northeast China, and these innovative systems in some areas had indicated favorable ecological, social, and economic benefits.

Toxicity Reduction of Municipal Wastewater by Anaerobic-anoxic-oxic Process

Objective This study was conducted to optimize the operational parameters of anaerobic-anoxic-oxic （A^2/O） processes to reduce the toxicity of municipal wastewater and evaluate its ability to reduce toxicity. Methods A luminescent bacterium toxicity bioassay was employed to assess the toxicity of influent and effluent of each reactor in the A2/O system. Results The optimum operational parameters for toxicity reduction were as follows： anaerobic hydraulic retention time （HRT） = 2.8 h, anoxic HRT = 2.8 h, aerobic HRT = 6.9 h, sludge retention time （SRT） = 15 days and internal recycle ratio （IRR） = 100%. An important toxicity reduction （%） was observed in the optimized A2/O process, even when the toluene concentration of the influent was 120.7 mg·L^-1. Conclusions The toxicity of municipal wastewater was reduced significantly during the A^2/O process. A^2/O process can be used for toxicity reduction of municipal wastewater under toxic-shock loading.

Advances in Energy-Producing Anaerobic Biotechnologies for Municipal Wastewater Treatment

Municipal wastewater treatment has long been known as a high-cost and energy-intensive process that destroys most of the energy-containing molecules by spending energy and that leaves little energy and few nutrients available for reuse, Over the past few years, some wastewater treatment plants have tried to revamp themselves as ＂resource factories,＂ enabled by new technologies and the upgrading of old technologies. In particular, there is an renewed interest in anaerobic biotechnologies, which can convert organic matter into usable energy and preserve nutrients for potential reuse. However, considerable technological and economic limitations still exist. Here, we provide an overview of recent advances in several cutting-edge anaerobic biotechnologies for wastewater treatment, including enhanced side- stream anaerobic sludge digestion, anaerobic membrane bioreactors, and microbial electrochemical systems, and discuss future challenges and opportunities for their applications. This review is intended to provide useful information to guide the future design and optimization of municipal wastewater treatment processes.

Performance evaluation of hybrid constructed wetlands for the treatment of municipal wastewater in developing countries

In developing countries,high cost of conventional wastewater treatment is a major hindrance in its application.Constructed wetlands(CWs)offer low-cost and effective solution to this issue.The current study aimed to evaluate an innovative maneuver of CWs i.e.hybrid flow constructed wetlands(HCWs)for municipal wastewater(MWW).The HCWs included two lab scale CWs;one horizontal and one vertical,in series.Local plant species were used.HCWs were operated in both,batch and continuous mode.Batch mode was used to(1)optimize detention time and(2)find pollutants removal efficiency.Continuous operation(at batch optimized retention time)was carried out for the evaluation of mass removal rate,r(g·m-2·d-1),volumetric rate constant,Kv(per day)and areal rate constant,Ka(m·d-1).Among two local plants tested,Pistia stratiotes gave better removal efficiency than Typha.Optimum detention time in HCWs was found to be 8 days(4+4 each).The optimum COD,BOD,TSS,TKN and P removal observed for Pistia stratiotes planted HCWs was 80%,84%,82%,71%and88%respectively.Effluent standards for COD,BOD and TSS were met at optimum conditions.The values of Kaand Kv demonstrated that more removal occurred in vertical flow as compared to horizontal flow CW.

Optimum municipal wastewater treatment plant design with consideration of uncertainty

A newly developed model for the optimum municipal wastewater treatment plant(MWTP) design is presented. Through introducing the interval variables, the model attempts to consider the effects of uncertainties caused by the fluctuation of the wastewater quality and quantity during the design of MWTP. The model solution procedure is illustrated in detail, and a numerical example is given to verify the feasibility and advantage of the model. Furthermore, the possibility of the model application is briefly outlined.

Countermeasures of Reclaimed Municipal Wastewater for Safety of Agricultural Use in China

China is facing a severe water resource crisis, and the shortage of water for agricultural consumption is a prominent problem. Irrigation with reclaimed municipal wastewater that can reach the agricultural recycling standards is an important way to deal with water shortage in agricultural production. Owing to the complex sources of municipal wastewater, there are multifarious pollutants in municipal wastewater. Improper use of wastewater can cause potential risks to agoenvironment, agricultural products safety, and human health. This article deals with the current situation and the development prospects of reclaimed wastewater for agricultural use in China and abroad; the potential risks to human health and environmental pollution from the reclaimed municipal wastewater for agricultural reuse are also discussed. And some countermeasures and advices of reclaimed municipal wastewater for safety of agricultural reuse are provided.

Nitrogen removal from municipal wastewater by limit-oxic/anoxic/oxic biological aerated filter system

In this study,a three-stage biological aerated filter(BAF) system was proposed for the enhancement of nitrogen removal in the treatment of low carbon-to-nitrogen ratio(C/N ratio) municipal wastewater.Operational parameters were studied for each process for maximum nitrite accumulation in the nitrification step and nitrite adaptation in the denitrification step.Nitrite accumulation during nitrification could be controlled by the dissolved oxygen(DO) concentration,presenting a mean value of 40% at around 1.0 mg DO/L.Denitrification could be adapted to nitrite and the process was stable if nitrite in the reactor was keep low.Once the operational parameters were established,the process was stable and a steady state was maintained for over 30 days,and the various indexes of discharged water were up to the Discharge standard of pollutants for municipal wastewater treatment plant(GB18918-2002) Level-one A.It was concluded that the three-stage BAF system proposed in this study was excellent in nitrogen removal performance by employing three-column functioning as short-cut nitrification,short-cut denitrification and secondary nitrification,respectively.

Optimization and application of fluorescent in situ hybridization (FISH) process in EBPR fed with municipal wastewater

For sludge samples from EBPR reactor fed with municipal wastewater,fluorescent in situ hybridization (FISH) operation process including moisture chamber,pretreatment,treatment with lysozyme and Proteinase K and washing time was optimized and improved.Preserving box was chosen to be moisture chamber due to its bigger depth /radii ratio,good sealability and big volume contrast with Petri dish.3-5 mm diameter glass balls could disperse samples without destroying microorganism cells and community structure.Impurities and ECPs could be removed easily and sludge samples became thinner after dispersing which benefit the observation.Permeabilized cells with lysozyme and Proteinase K could enhance probe penetration before hybridization.Experiments of different treatment time with lysozyme and Proteinase K were carried out.Best results were observed when sludge samples treated with lysozyme 10 min/Proteinase K 20 min or lysozyme 20 min/Proteinase K 10 min.Slides were washed at 48 ℃ for 10,20,30,40 and 60 min in parallel.The best washing time was 20 min when washing temperature was 48 ℃.Fluorescent dye could residue when washing time was 10 min and washing out happened when washed for 30 min or more.

Approaches to municipal wastewater irrigation and environmental protection

To reuse the water and nutrient resources from ecological point of view the goals, criteria and constraint conditions of the scientifically municipal wastewater irrigation are discussed as well as the practice in major municipal wastewater irrigation areas in China is introduced, of which particularly the effects of municipal water irrigation mixing with oil refinery wastewater on the agricultural ecosystem are studied and described. It has been revealed that benzo(a)pyrene in various parts of paddy crop is attributed to air pollution, water-soil pollution and biosynthesis of plant. Of exogenous contributions of benzo(a)pyrene in paddy shoot system under natural condition, the dominant factor is the air pollution, whereas the water-soil factor is considered to be secondary. Therefore, it is mostly urgent to control the air pollution source of benzo(a)pyrene, to which the edible parts of various green plants are exposed directly.

Reed-wetland beds for municipal wastewater treatment

The performance of 11 reed-wetland beds for municipal wastewater treatment is described in this paper. The interrelation between pollutants removal (BOD5, SS, N and P) and hydraulic loading rate, organic loading rate, hydraulic retention time as well as the seasonal variation could be found in this study. The treatment efficiencies of reed beds are better than the secondary treatment standards with high and steady nitrogen and phosphorus removal. The total nitrogen and phosphorus of the final effluent are less than 10 mg/L and 0.5 mg/L, respectively.

Characteristics of integrated biological aerated filter in municipal wastewater treatment

In this paper, the characteristics of integrated biological aerated filter (IBAF) applied to municipal wastewater treatment were studied in a pilot scale experiment. The experimental results showed that IBAF has high efficiencies in removing organic pollutants, such as CODCr and SS, in municipal wastewater. The removal rates of CODCr and SS can reach over 90% and 80%, respectively, when COD and SS in the influent are 234 mg L1 and 112 mg L1, hydraulic retention time (HRT) is 8 h, and the aerated intensity is in the range of (0.5 to 0.6) L m2 s1.

A New Method for Comparing Hospital and Municipal Wastewater

The objective of this study is to investigate the differences in organic compounds that are present in hospital and municipal wastewater samples. Two samples with the same COD （chemical oxygen demand） values were chosen for this study. The results have shown that both samples consist of the same compounds with low molecular weights and high polarities in high concentrations. The hospital wastewater consisted of more compounds arithmetically. Differences were found in the organic compound with low molecular weight and low polarities. Pharmaceutical compounds such as caffeine, acetanilide and phenacetin were detected only in the hospital wastewater.

Full Scale SBR Municipal Wastewater Treatment Facility Utilization of Simultaneous Nitrification/Denitrification Coupled with Traditional Nitrogen Removal to Meet Water Criterion

Simultaneous nitrification denitrification (SND) is a well-established phenomenon in biological nutrient removal activated sludge systems. Study at a municipal wastewater treatment facility sought to determine nitrogen removal effectiveness within a full-scale sequential batch reactor (SBR) system utilizing SND in conjunction with traditional nitrogen removal. In addition to characterizing extent of SND, the research examined the ability of SND to meet state-based effluent water quality standards. At the selected facility, the average SND efficiency during a two-month sampling period was 52.8%, paralleling results from similar SBR municipal wastewater systems. The observed SBR system had removal efficiencies > 99% for the influent to effluent -N concentrations. The SND process also resulted in average NO3-NO2-N concentration that was 82% lower than the theoretical concentration under comparable circumstances. Overall, nitrogen removal for this SBR system was >99% which typified results in other SND systems, but at a higher Total Nitrogen removal rate.

Methane and nitrous oxide emissions from municipal wastewater treatment plants in China:A plant-level and technology-specific study

Wastewater treatment is an important source of greenhouse gases(GHGs).Yet large uncertainties remain in the quantification of GHG emissions from municipal wastewater treatment plants(MWWTPs)in China.A high-resolution and technology-specific emission inventory is still lacking to support mitigation strategies of MWWTPs.Here we develop a plant-level and technology-based MWWTP emission inventory for China covering 8703 plants and 19 treatment technology categories by compiling and harmonizing the most up-to-date facility-level databases.China's methane(CH_(4))and nitrous oxide(N_(2)O)emissions from MWWTPs in 2020 are estimated to be 150.6 Gg and 22.0 Gg,respectively,with the uncertainty range of-30%to 37%and-30%to 26%at 95%confidence interval.We find an emission inequality across cities,with the richest cities emitting two times more CH_(4)and N_(2)O per capita from municipal wastewater treatment than the poorest cities.The emitted CH_(4)and N_(2)O are dominated by Anaerobic/Anoxic/Oxic-,Sequencing Batch Reactor-,Oxidation Ditch-,and Anoxic/Oxic-based MWWTPs of less than 20 years old.Considering the relatively young age structure of China's MWWTPs,the committed emissions highlight the importance of reducing on-site GHG emissions by optimization of operating conditions and innovation management.The emission differences among our estimates,previous studies,and the Intergovernmental Panel on Climate Change guidelines are largely attributed to the uncertainties in emission factors,implying the urgent need for more plant-integrated measurements to improve the accuracy of emission accounting.

Monitoring of 943 organic micropollutants in wastewater from municipal wastewater treatment plants with secondary and advanced treatment processes

To perform a systematic survey on the occurrence and removal of micropollutants during municipal wastewater treatment, 943 semi-volatile organic chemicals in 32 wastewater samples including influents of secondary treatments, secondary effluents and final effluents（effluents of advanced treatments）, which were collected from seven full-scale municipal wastewater treatment plants（MWTPs） in China, were examined by gas chromatography-mass spectrometry（GC-MS） coupled with an automated identification and quantification system with a database（AIQS-DB）. In total, 196 and 145 chemicals were detected in secondary and final effluents, respectively. The majority of the total concentrations（average removal efficiency, 87.0%±5.9%） of the micropollutants were removed during secondary treatments. However, advanced treatments achieved different micropollutant removal extents from secondary effluents depending on the different treatment processes employed. Highly variable removal efficiencies of total concentrations（32.7%–99.3%） were observed among the different advanced processes. Among them,ozonation-based processes could remove 70.0%–80.9% of the total concentrations of studied micropollutants. The potentially harmful micropollutants, based on their detection frequency and concentration in secondary and final effluents, were polycyclic aromatic hydrocarbons（PAHs）（2-methylnaphthalene, fluoranthene, pyrene, naphthalene and phenanthrene）, phosphorus flame retardants（tributyl phosphate（TBP）, tris（2-chloroethyl）phosphate（TCEP） and tris（1,3-dichloro-2-propyl） phosphate（TDCP））, phthalates（bis（2-ethylhexyl）phthalate（DEHP））, benzothiazoles（benzothiazole,2-（methylthio）-benzothiazol, and 2（3H）-benzothiazolone） and phenol. This study indicated that the presence of considerable amounts of micropollutants in secondary effluent creates the need for suitable advanced treatment before their reuse.

Sludge fermentation liquid addition attained advanced nitrogen removal in low C/N ratio municipal wastewater through short-cut nitrification-denitrification and partial anammox

Biological nitrogen removal of wastewater with low COD/N ratio could be enhanced by the addition of wasted sludge fermentation liquid(SFL),but the performance is usually limited by the introducing ammonium.In this study,the process of using SFL was successfully improved by involving anammox process.Real municipal wastewater with a low C/N ratio of 2.8–3.4 was treated in a sequencing batch reactor(SBR).The SBR was operated under anaerobic-aerobic-anoxic(AOA)mode and excess SFL was added into the anoxic phase.Stable short-cut nitrification was achieved after 46d and then anammox sludge was inoculated.In the stable period,effluent total inorganic nitrogen(TIN)was less than 4.3 mg/L with removal efficiency of 92.3%.Further analysis suggests that anammox bacteria,mainly affiliated with Candidatus_Kuenenia,successfully reduced the external ammonia from the SFL and contributed approximately 28%–43%to TIN removal.Overall,this study suggests anammox could be combined with SFL addition,resulting in a stable enhanced nitrogen biological removal.

Performance and mechanistic study on electrocoagulation process for municipal wastewater treatment based on horizontal bipolar electrodes

The design of electrodes is crucial to electrocoagulation process(EC),specifically,with respect to pollutant removal and energy consumption.During EC,the mechanisms for interaction between different electrode arrangement and electrode reactions remain unclear.This work presents an integrated EC process based on horizontal bipolar electrodes(BPEs).In the electrochemical cell,the graphite plates are used as driving cathode while either Fe or A1 plates serves as driving anode and BPEs.The BPEs are placed horizontally between the driving electrodes.For municipal wastewater treatment,the pollutant removal efficiency and energy consumption in different configurations of twodimension electrocoagulation(2D-EC)system with horizontal BPEs were investigated.The removal efficiency of turbidity,total phosphorus and total organic carbon increased significantly with the number of BPEs.Noted that the energy consumption for TP removal decreased by 75.2%with Fe driving anode and 81.5%with A1 driving anode than those of 2D-EC,respectively.In addition,the physical field simulation suggested the distributions of potential and current in electrolyte and that of induced charge density on BPE surface.This work provides a visual theoretical guidance to predict the distribution of reactions on BPEs for enhanced pollutant removal and energy saving based on electrocoagulation process for municipal wastewater treatment.

Feedforward control for nitrogen removal in a pilot-scale anaerobic-anoxic-oxic plant for municipal wastewater treatment

To improve the efficiency of nitrogen removalwith lower energy consumption,the study of feedforwardcontrol was carried out on a pilot-scale anaerobic-anoxicoxic(AAO)plant for the treatment of municipal wastewater.The effluent qualities of the pilot plant underdifferent control strategies were investigated.The resultsindicated that the change of external recycle was not asuitable approach to regulate the sludge concentration ofplug-flow reactors;adjusting the aeration valve anddissolved oxygen set-point according to ammonia loadcould overcome the impact of influent fluctuation;and thedenitrification potential could be estimated based on thetransit time of anoxic zone and the relative content ofcarbon resource entering the anoxic zone.Simple feedforwardcontrol strategies for aeration and internal recyclewere subsequently proposed and validated.The nitrogenremoval was successfully improved in the pilot plant.Theeffluent total nitrogen had decreased by 29.9%and wassteadily controlled below 15 mg·L^(-1).Furthermore,approximately 38%of the energy for aeration had beensaved.