Oraganic Matter Traits And Water Quality Biostable Technique In Township Water Supply Pipe Network

In recent years,much attention has been paid to establish an urban and rural co-operation water supply system in Jiangsu Province.However,the variation of the organic matter property and the biological stability in long-distance water supply networks are rarely noticed in most cases.The goal for this research is exploring the difference of organic matter property in long-distance water pipe network and ensuring the biological stability of the water quality of the pipe network,which is based on the project of urban and rural integrated regional water supply in Y city.First,we conducted research on the water supply network of two typical townships,then analyzed the regular water-quality indices,organic matter level and microbial marker.Based on these aforementioned results,the effects of different chlorination methods on the characteristics of organic matter in long-distance water distribution network were elucidated,and the key factor affecting the biological stability of water was proposed.On the basis of the water quality in the township pipe network in the dry season?January?,the flood season?June?,and the flat water period?September?,some results were obtained and shown as follows:the residual of chlorine and the turbidity level in the water of the two selected townships was seriously exceeded.The seasonal variations of Dissolved Organic Carbon?DOC?and UV₂₅₄ were considerable,which exhibited an enhancement in summer and a suppression in winter,and was opposite to that of oxygen consumption.Disinfection By-Products?DBPs?in pipe network water were dominated by Trihalomethanes?THMs?and possessed a high summer and low winter distribution pattern,while that of Disinfection By-Products Formation Potential?DBPsFP?was inverse.These results suggested a trend of dimishing with the distance of the pipe network.The utilization of a statistical application software was performed and the result confirmed that there was a significant negative correlation between oxygen consumption and DOC,while that between DOC and UV₂₅₄ was positive.Moreover,there was a significant positive correlation between DOC and Trihalomethanes Formation Potential?THMsFP?as well as DOC and Haloacetic Acids Formation Potential?HAAsFP?.Additionally,the variation of organic matter characteristics in long-distance water distribution network was explored in depth using the pilot-plant.The effects of residual chlorine,turbidity,flow rate,pipe and temperature on the biological stability of pipe network water were also investigated.The main conclusions are as follows:The concentration of DOC in the pipe network water increased whenever chlorine was added.However,the neutral hydrophilic organics still maintained a high proportion in the fourth organic components,and the organic matter variations of other components were negligible.At the beginning of the experiment,small molecular organic matter of 1 kDa was dominant in tap water.Then,the proportion of organic matter over 3 kDa gradually increased.When the initial concentration of chlorine enhanced,the enhancement of macromolecular organic matter was delayed.It should be noticed that the total amount of DBPsFP was the lowest when the concentration of chlorine is 0.60 mg/L.Polar hydrophilic organics were the main source of DBPsFP followed by hydrophobic organics.When tap water contained residual chlorine,neutral hydrophilic organic matter became the main cause of bio-unstability,followed by hydrophobic organic matter.Under multi-stage chlorination,DOC and UV₂₅₄increased continuously with the enhancement of the residence time.Neutral hydrophilic organics were still the highest proportion in the three sets of experiment.It was confirmed that polar hydrophilic organics increased substantially when the chlorine dosage was 1.60 mg/L.When the chlorine dosage was 0.60 mg/L,the small organic matter below 1 kDa occupied the most proportion in water,and those over 100 kDa were rarely detected.When the chlorine content enhanced to 1.0 mg/L,the organic molecules of 3-10 kDa became dominant.When the chlorine concentration was 1.60 mg/L,the organic molecules of 10-100 kDa occupied a large proportion.These results indicated that the concentration of chlorine highly influenced those of organic molecules with different molecular weights.Finally,the biological stability was also investigated.In the case of single chlorination,the increase of chlorine content was not significant for the elevation of Assimilable Organic Carbon?AOC?,and that of Biodegradative Dissolved Organic Carbon?BDOC?was opposite.In the case of multi-stage chlorination,both AOC and BDOC increased with increasing residence time.At the same time,the elevation of turbidity would increase the concentration of AOC and BDOC,also the growth rate of Heterotrophic Plate Count?HPC?would be faster when the increaseing of turbidity.The concentration of AOC and BDOC in PE pipes was the highest,followed by steel pipes and galvanized steel pipes,the lowest was in ductile iron pipe.The concentrations of HPC in different pipes was in order of PE pipe>ball-milled cast iron pipe>galvanized steel pipe>steel pipe.When the flow rate increased,both AOC and BDOC in the pipe network water enhanced correspondingly.The enhanced temperature caused the increase of DOC,AOC,and BDOC in the water.The result of statistical analysis confirms that the THMsFP exhibited a significant positive correlation with AOC.Multi-stage chlorine and flow rate also showed a significant positive correlation with AOC in pipe network water.Both multi-stage chlorine dosage and turbidity showed significant positive correlations with BDOC.