城市用水水处理分析

对城市用水情况进行了分析,阐述我国城市用水水处理发展的最新动态,总结了城市用水水处理氯消毒是核心,展望了城市用水水处理所存在的巨大市场前景。

2008—2012年横县农村饮用水卫生调查结果与分析

目的为掌握农村饮用水水质卫生现状及其变化趋势,评估农村饮水安全工程的卫生防病效果,为政府决策提供科学依据。方法对2008-2012年农村人饮工程的基本情况、水源类型和供水方式等进行现场卫生调查,按丰水期、枯水期采集出厂水和末梢水进行检验分析。结果横县农村人饮工程选址合理,水源类型主要以地下深水井为主,水处理率、水质合格率逐年提高,2012年调查发现,横县农村人饮工程水质完全处理率为3.40%,消毒处理率达37.86%,完全未处理率为58.74%,水质检验平均合格率为41.74%,结论横县人饮工程较好地解决了群众人饮困难问题,但部分工程仍存在微生物超标、感官不合格和部分理化指标不合格等现象,有待政府加大投入,明确建管主体职权,完善和落实消毒制度,多部门齐抓共管,形成长效管理机制,确保群众饮水安全。

Extractable Fractions of Metals in Sewage Sludges from Five Typical Urban Wastewater Treatment Plants of China

Metal content and bioavailability are often the limiting factors for application of sewage sludge in agricultural fields. Sewage sludge samples were collected from five typical urban wastewater treatment plants in China to investigate their contents and distribution of various chemical fractions of Cu, Zn, Ni, Cr, Pb and Mo by using the BCR （Community Bureau of Reference） sequential extraction procedure. The sludges contained considerable amounts of organic matter （31.8%- 48.0%）, total N （16.3-26.4 g kg^-1） and total P （15.1-23.9 g kg^-1）, indicating high potential agricultural benefits of their practical applications. However, total Zn and Ni contents in the sludge exceeded the values permitted in China＇s control standards for pollutants in sludges from agricultural use （GB 4284-1984）. The residual fraction was the predominant fraction for Mo, Ni and Cr, the oxidizable fraction was the primary fraction for Cu and Pb, and the exchangeable and reducible fractions were principal for Zn. The distribution of different chemical fractions among the sludge samples refiected differences in their physicochemical properties, especially pH. The sludge pH was negatively correlated with the percentages of reducible fraction of Cu and exchangeable fraction of Zn. The sludges from these plants might not be suitable for agricultural applications due to their high contents of Zn, Ni and Cr, as well as high potential of mobility and bioavailability of Zn.

The flocculation efficiency of compound bioflocculant by flocculant-producing bacteria

The flucculation efficiency of compound bioflocculant produced by flocculant-producing bacteria was investigated in this study. Cheap cellulose was selected as the substrate for the production of a lower cost bioflocculant. The end product of cellulose decomposing bacteria was utilized as substrate for flocculant-producing bacteria. The optimum fermentation conditions were determined as follows： the initial fermentation and fermentation time was 5 d and 1 d respectively, the temperature was 30 ℃, the rotation speed was 120 r/min, the amount of CaCl2 solution （ 10% ） was 1.5 ml/L. The flocculation test indicated that the bioflocculant had high efficiency in the removal of the turbldity raw water from Songhua River.

Treatment performance of integrated biological aerated filter by orthogonal experiments

Biological aerated filters have many advantages such as small volume and high treatment efficiency. This research focused on sewage treatment performance of integrated biological aerated filter (IBAF) under different conditions such as aeration, hydraulic retention time and the height of fillers layer, to identify the turn of marked affecting factor of removal performance through orthogonal experiments, optimize the function parameter of IBAF, reveal the regularity of sewage treatment of IBAF under different conditions, and adopt suitable measures to guarantee excess water quality of IBAF.

Degradation of Wastewater Containing Nitrobenzene by High Gravity-Ultrasonic/Ozonation/Electrolysis Technology

The integrated high gravity-ultrasonic/ozonation/electrolysis technology was applied in the pretreatment of wastewater containing nitrobenzene. The effect ofpH value, high gravity factor, liquid flow-rate and electric current density on removal of COD and nitrobenzene compounds was investigated. Experimental results have determined the optimal pro- cess regime involving a high gravity factor of 100, an electric current density of 20 mA/cm2, a liquid flow-rate of 100 L/h, and an initial liquid pH value of 11. After the wastewater had been treated for 180 rain, the degradation of nitrobenzene and COD reached 99% and 80%, respectively, with the biochemical coefficient （BOD/COD） equating to 0.64, and the subse- quent treatment of wastewater could be carried out by conventional biochemical means. Compared with traditional aeration- ozone contactors, a rotating packed bed with high mass transfer characteristics could be used to increase the ozonation treat- ment efficiency.

Comparison of heavy metal removal efficiencies in four activated sludge processes

The removal efficiencies of heavy metals(As, Cr, Cu, Ni, Pb and Zn) were investigated in the 17 operating municipal wastewater treatment plants(WWTPs) and compared with those in four main activated sludge processes. Significant differences of heavy metal removal efficiencies were observed among four activated sludge processes. The removal efficiency for As(75.5%) in the oxidation ditch(OD) process is significantly higher than that in the conventional activated sludge(CAS) process(38.6%) or sequencing batch reactor(SBR) process(51.4%). The mean removal efficiencies for Cu and Ni in the OD process are 90.5% and 46.7%, respectively, while low mean removal efficiencies are observed for Cu(69.9%) and Ni(16.5%), respectively, in the SBR process. The removal efficiencies for Cu and Ni in the OD process are significantly higher than those in the anaerobic-anoxic-oxic(A2-O) process. These results highlight the differences of removal efficiencies for heavy metals in different processes and should be considered when selecting a wastewater treatment process.

Extraction of Cadmium from Sewage Sludge Using Polyepoxysuccinic Acid

Polyepoxysuccinic acid （PESA）, as an environmental benign biodegradable chelant, was used to remove heavy metals from the sewage sludge of Shanghai Taopu Wastewater Treatment Plant. The extraction of cadmium （Cd） from sewage sludge using aqueous solution of PESA was studied. It was found that PESA was capable of extracting Cd from the sludge, and the extraction efficiency was dependent on both pH and the concentration of the chelating reagent. The extraction efficiency decreased gradually with increasing of pH, whereas the dependency on pH decreased as the concentration of PESA increased. In the case of the high PESA to total metal ratio, e.g., 10：1, the extraction efficiency reached above 70% within the pH range from 1 to 7. The highest extraction efficiency obtained in tbe experiment was 78%. By comparing the contents of the heavy metals in sewage sludge before and after the extraction, it was found that the extracted Cd came mainly from the four fractions： acid-soluble, reducible, oxidizable, and water-soluble fractions.

Change of Ecological Characteristics Due to Decrease of COD/SO_4^(2-) Ratio During Sulfate-reduction

In order to investigate the change of ecological characteristics due to the decrease of COD/SO_4^(2-) ratio during sulfate reduction, continuous-flew tests were conducted in an acidogenic sulfate-reducing reactor with molasses wastewater as sole organic carbon source and sodium snlfate as electron acceptor, and the change of pH value, oxidation reduction potential (ORP), volatile fat acids (VFAs), alkalinity (ALK) and the predominant populations with COD/SO_4^(2-) ratio decreasing from 4.2 to 2.0 were investigated. The experimental results demonstrated that, with decreasing COD/SO_4^(2-) ratio, ORP and ALK increased, pH value decreased, and the proportion of acetic acid in terminal products decreased significantly, and a stable -type microbial community with high COD/SO_4^(2-) ratio was converted into a sub -stable -type one with low COD/SO_4^(2-) ratio.

Determination of 4-nonylphenol and 4-tert-octylphenol compounds in various types of wastewater and their removal rates in different treatment processes in nine wastewater treatment plants of Iran

Alkylphenols(APs), considered as xenoestrogenic compounds, mainly exist as 4-nonylphenol(4-NP) and 4-tertoctylphenol(4-t-OP) in environments. The high stability and accumulation of APs in aquatic systems have caused endocrine disruption. In this study we measured APs in the wastewater influent and effluent samples, from the urban, rural, livestock, commercial and hospital wastewater treatment plants(WWTPs) in Iran. Dispersive liquid–liquid microextraction(DLLME) combined with gas chromatography–mass spectrometry(GC–MS) was used for the extraction and determination of 4-NP and 4-t-OP. In these treatment plants, various processes such as activated sludge, aerated lagoon, moving bed biofilm reactor and activated sludge along with wetland were applied. The highest concentration of 4-NP and 4-t-OP was observed in commercial and livestock sewages. The activated sludge along with wetland and then the MBBR process showed the highest removal rates of pollutants. The rates of biodegradability and accumulation in sludge were determined and also the specific adsorption coefficient Kdand the organic carbon–water partition coefficient kOCof the sludge for APs were calculated.

Reactions Between Humic Acid Solutions and Excessive ClO_2 or Cl_2

Reactions between humic acid solutions and excessive ClO2 or Cl2 have been investigated. Under various experimental conditions, the removal efficiency of TOC, UV254and A410 from humic acid solutions were examined. The relationship between the removal efficiency and the consumption of ClO2 or Cl2 was discussed. The results showed that the maximum demand of ClO2 was 2.19 mg/mg TOC for the humic acid solution under the experimental conditions, and that of ClO2 was 1.88 mg/mg TOC. The variation tendency of ClO2 consumption was similar to that of Cl2. TOC of humic acid solutions decreased 15.2% and 15.6% after the reaction with ClO2 or Cl2 respectively. Under the experimental conditions, 21.4% of unsaturated bonds and 52.8% of humic acid color were removed by ClO2 in 168 h. As for Cl2, removal efficiency of unsaturated bonds and humic acid color were 16.8% and 41.7% respectively. Larger molecules from humic acid were oxidized to smaller molecules by ClO2 and Cl2. Higher oxidation potential of ClO2 than that of Cl2 was also indicated by variation of UV254/A410 ratios. The similar tendency, that exhibited faster variation in the initial 24 h, existed for all the research factors.

Multi-objective steady-state optimization of two-chamber microbial fuel cells

A microbial fuel cell(MFC)is a novel promising technology for simultaneous renewable electricity generation and wastewater treatment.Three non-comparable objectives,i.e.power density,attainable current density and waste removal ratio,are often conflicting.A thorough understanding of the relationship among these three conflicting objectives can be greatly helpful to assist in optimal operation of MFC system.In this study,a multiobjective genetic algorithm is used to simultaneously maximizing power density,attainable current density and waste removal ratio based on a mathematical model for an acetate two-chamber MFC.Moreover,the level diagrams method is utilized to aid in graphical visualization of Pareto front and decision making.Three biobjective optimization problems and one three-objective optimization problem are thoroughly investigated.The obtained Pareto fronts illustrate the complex relationships among these three objectives,which is helpful for final decision support.Therefore,the integrated methodology of a multi-objective genetic algorithm and a graphical visualization technique provides a promising tool for the optimal operation of MFCs by simultaneously considering multiple conflicting objectives.

Experimental Investigation of Environmental Hydraulic Parameters for Dual Mixed Media Biofilter for Greywater Treatment

Laboratory scale model of DMMBF （dual mixed media biofilter） were designed and installed in AI-Mustansiriya University Environmental Hydraulic Lab. Experiments were conducted using two mixed layers through PVR column--2.2 m height and 300 mm diameter. The first mixed media filter of depth 640mm mixed of sand, rice husk and granular activated carbon. The percentage volume mix is 1：1：1. While the other mixed media of depth 740 mm, consisting of coal, crash porcelinaite, rock and granite with equally percentage volume. Fifty samples were collected during the experiments, which was spread over a period of forty two weeks. The obtained results indicate that when the flow loading raised from 0.15 L/min to 2.7 L/rain, the removal efficiency of BOD decreased 8%-11%, and the removal efficiency of COD deceased 3%-4%, while the removal efficiency of turbidity increased with the decreasing of hydraulic loading. The results showed that the removal efficiency of turbidity is more than 95% at the lower discharge （0.15 L/min）. Therefore, infiltration should be conservatively designed using low loading rates.

Biological treatment of high NH_4^+-N wastewater using an ammonia-tolerant photosynthetic bacteria strain (ISASWR2014)

Wastewater with high NH_4^+-N is difficult to treat by traditional methods.So in this paper,a wild strain of photosynthetic bacteria was used for high NH_4^+-N wastewater treatment together with biomass recovery.Isolation,identification,and characterization of the microorganism were carried out.The strain was inoculated to the biological wastewater treatment unit.The impacts of important factors were examined,including temperature,dissolved oxygen,and light intensity.Results showed that photosynthetic bacteria could effectively treat high NH_4^+-N wastewater.For wastewater with NH_4^+-N of 2300 mg·L^(-1),COD/N=1.0,98.3%of COD was removed,and cell concentration increased by 43 times.The optimal conditions for the strain's cell growth and wastewater treatment were 30℃,dissolved oxygen of 0.5-1.5 mg·L^(-1) and a light intensity of 4000 lx.Photosynthetic bacteria could bear a lower C/N ratio than bacteria in a traditional wastewater treatment process,but the NH_4^+-N removal was only 20%-40%because small molecule carbon source was used prior to NH_4^+-N.Also,the use of photosynthetic bacteria in chicken manure wastewater containing NH4+-N about 7000 mg·L^(-1) proved that photosynthetic bacteria could remove NH_4^+-N in a real case,finally,83.2%of NH_4^+-N was removed and 66.3%of COD was removed.

Modified two-phase anaerobic baffled process for low-concentration wastewater treatment

In this study low-concentration wastewater was investigated in the integral two-phase anaerobic baffled reactor by determining the removal of COD at various HRT,reflex ratios,and temperatures. Results indicate that the removal efficiency of COD is more than 90% at 25 ℃ and 10-h HRT with no wastewater recycled,and the removal efficiency is up to 88% at 8-h HRT and reflex ratio of 150%. The removal efficiency is decreased with the decreasing temperature and HRT. The removal efficiency of COD is approximately 60% at 10 ℃,which proves that the temperature does not affect it apparently. This research has significance for reducing the cost of wastewater and sludge treatment in cold area.

Discussion on nitrogen and phosphorus removal process characteristics of improved oxidation ditch

In order to enhance efficiency of the nitrogen and phosphorus removal of sewage treatment plant, Taking Wu Long kou sewage treatment plant project in Zhengzhou as an example, this article introduces the structure, the working principle, the craft character, as well as the problems existed in the practical application of the improved oxidation ditch, and raises some corresponding processing countermeasures. Looked from the running situation of Wu Long kou sewage treatment plant, the improved oxidation ditch have certain advantages in city sewage treatment, such as high organic removing efficiency, good removing effect of nitrogen and phosphorus, low investing expenses and operating cost and so on. It is a craft that is worth promoting in urban sewage treatment.

Experimental Research on Coke Wastewater Treatment by Hybrid Biological Reactor

Phase hybrid biological reactor （HBR） was used in treating coke wastewater by adding submerging fiber-ball fillers in suspended growth activated sludge. The optimum operation parameters for the highest performance were determined. It was found that the hybrid biological reactor worked well for the coke wastewater treatment in terms of Chemical Oxygen Demand （COD）, NH4＋ -N and other refractory organic compounds removal efficiencies. Compared with conventional activated sludge system, the removal rate of COD and NH4＋ -N and the nitrating rate were higher and more stable in the hybrid biological reactor. COD of effluent was less than 75 mg/L and the removal rate of COD and NH4＋ -N could be up to 95.0% and 92.5% when COD of influent and NH4＋ -N were less than 700 mg/L and 300 rag/L, respectively. In this way, the quality of effluent concentration could reach the first class of integrated wastewater discharge standard （GB8978-1996） （COD ≤100 mg/L）.

Treatment of Domestic Sewage by Two-Stage-Bio-Contact Oxidation Process

Effects of hydraulic retention time (HRT ) and gas volume on efficiency of wastewater treatment are dis- cussed based on a simulation experiment in which the domestic swage was treated by the two-stage-bio-contact oxida- tion process. The result shows that the average CODCr, BOD5 , suspended solid (SS), and ammonia-nitrogen removal rate are 94.5 %, 93.2 %, 91.7 % and 46.9 %, respectively, under the conditions of a total air/water ratio of 5∶1 , an air/water ratio of 3:1 for oxidation tank 1 and 2:1for oxidation tank 2and a hydraulic retention time of 1 h for each stage. This method is suitable for domestic sewage treatment of residential community and small towns as well.

Preparation of Cationic Chitosan-Polyacrylamide Flocculant and Its Properties in Wastewater Treatment

Chitosan derived from crab shells, was used to prepare the graft polymer in aqueous solution with acrylamide （AM） and methacrylatoethyl trimethyl ammonium chloride （DMC） as raw materials and ceric ammonium nitrate （CAN） as initiator. The flocculation ability of the resulting polymer （PCAD） was studied in waste water treatment experiments. Its properties were determined on the basis of the transmittance of waste water after flocculation. The effects of ehitosan and DMC content on PCAD＇s flocculation ability were studied. Floeculation experiments were also undertaken under various pH conditions. According to the experimental data, the flocculation ability could be improved when chitosan content decreased in the raw material, but the monomer conversion would decrease obviously. When the ehitosan＇s content was more than 65%, AM and DMC groups were less on each chitosan molecule. So PCAD＇s flocculation ability was poor. Similarly, high content of DMC would result in low monomer conversion and high flocculation ability. PCAD molecules with more DMC group had more positive charges. It was favorable to flocculation. However, monomer conversion would decrease with the increase of DMC content. The suitable conditions were that chitosan and DMC contents were 65% and 15-20%, respectively. The experiment data showed that PCAD had good flocculation ability under weak acidic condition. Its ability would be weakened by strong acidic or alkaline condition. The flocculation efficiency was the best at pH of 5.5 when PCAD＇s dosage was 8mg-Lk Compared with cationic polymer （the copolymer of AM and DMC, PAD）, PCAD showed better flocculation ability under acid and neutral conditions, but worse ability under alkaline condition.

Removal of Microcystin-LR in Water by Chlorine Dioxide

Microcystins （ MCs ） are well known as hepatotoxins produced by blooms of toxic cyanobacteria （blue-green algae） abundant in surface water used as drinking water resource and have drawn attention of environmentalists world over by leading to adverse health effects. A study on efficiency and reaction kinetics of microcystin-LR （ MC-LR ） degradation by CIO2 was performed. Experimental results indicated that MC-LR was removed by CIO2 effectively and the residual concentration of MC-LR could meet the national guideline（GB5749 - 2006） （1.0 μg · L^-1）, the efficiency of removal was in positive correlation to CIO2 dosage and reaction time and in negative correlation to initial concentration of MC-LR and pH value, whereas it was affected by temperature slightly. CIO2 dosage was the most important reaction factor on base of the orthogonal test results. The reaction was second order overall and first order with respect to both CIO2 and MC- LR, and had an activation energy of 78.81 kJ · mo1^-1 . The reaction rate constant was 4.74× 10-^2 L/（mol · min） at 10 ℃. Therefore, oxidation of CIO~ could be taken as an effective technology for removing MC-LR from drinking water resources in traditional drinking water supplies.