Study On The Identification And Supervision Plan Of The Priority Control Area Of ??rural Domestic Sewage Treatment Facilities In Jiaxing City

China has a large rural population,and its domestic sewage discharge is large,but the treatment rate is low.The impact of rural domestic sewage on the surface water environment has been widely concerned.In recent years,many rural sewage treatment facilities have been built in China.These facilities are huge in number and scattered in location,which brought great difficulty in maintenance and supervision.This paper takes Jiaxing City,a plain river network area in the middle and lower reaches of the Yangtze River Delta,as a research object.Firstly,the basic information database of rural sewage treatment facilities in Jiaxing city was established.Then,the process and scale distribution characteristics of the facilities in subordinate districts?counties?were statistically analyzed.After that,through a large number of field surveys and water quality tests,the effluent quality was evaluated.Finally,Xiuzhou district and Haining city were selected as examples to study the method of identifying the priority control area of rural domestic sewage treatment facilities with township zoning as the unit,and work out an efficient and economical operation and maintenance supervision plan.The research results can provide technical support for grasping the status quo of facility operation and improving the efficiency of facility operation and maintenance supervision.The research results showed that:?1?A total of 2142 rural domestic sewage treatment facilities with a treatment scale of 1 t·d^-1 or above have been operated and maintained in jiaxing.Among them,the scale of 1?20t·d^-1(excluding20 t·d^-1)accountsfor 68.4%.The anaerobic-anoxic-oxic contact oxidation type?AAO?facilities accounted for 68.2%of the total number of facilities in Jiaxing city.Among the districts?counties or cities?,the scale of facilities in Pinghu county,Haiyan county and Jiashan county was of mainly 20?50 t·d^-1,and the scale of facilities in other districts?counties?was of mainly 1?20 t·d^-1.AAO process facilities were dominant in all districts?counties?except in Gangqu district,where ITE was widely used.?2?The effluent quality of 167 rural domestic sewage treatment facilities was sampled and compared with the second-level discharge standard of"Zhejiang rural domestic sewage treatment facilities water pollutant discharge standard"?DB33/9732015?.The results showed that the compliance rate of COD was of the highest,98.2%in Jiaxing city.The rate of achievement of all four indicators was 48.8%.The compliance rate of NH₃-N and TP showed little dependence on the facilities scale,however,the compliance rate of COD and SS increased with the increase in the scale of facilities.Those facilities of 20?50 t·d^-1 showed the highest overall compliance rate.Among various processes,ABT+PKA and BFP facilities showed the best pollutant removal performance.The rate of achievement of all four indicators was 66.7%and81.8%.Haining county,Jiashan county and Xiuzhou district were listed as the top three,in which the total compliance rate of the four indexes being 76.3%,66.7%and53.2%,respectively.?3?The pollutant emission intensity of rural domestic sewage treatment facilities in Xiuzhou district and Haining county was analyzed.It was found that the NH₃-N and COD emission intensity of rural domestic sewage treatment facilities in Xiuzhou district was significantly higher than that in Haining county,while the TP emission intensity was almost the same.Each district?county?inside different town?street?blowdown intensity difference was very big.In Xiuzhou district,the discharge intensity was highest in Honghe town for all pollution indexes.While in Haining county,the highest emission intensity was in Yanguan town for NH₃-N,but in Xucun town for TP and COD.?4?In order to improve the supervision efficiency,the priority control areas of rural sewage treatment facilities in Xiuzhou district and Haining county were studied.From 470 facilities in five towns in Xiuzhou district,three towns?Honghe town,Wangjiangjing town and Youchegang town?were selected as the priority control area.By focusing on the management of facilities of different sizes,such as 50 t·d^-1 above Wangjiangjing town and 30?50 t·d^-1Youchegang town,the pollutant discharge reduction of 60.0%could be achieved through the supervision of 17.7%facilities.From 178 facilities in 11 towns of Haining county,five towns?Changan town,Xucun town,Haizhou street,Yanguan town and Yuanhua town?were selected as the priority control area.Through the key management of facilities of different sizes,such as 50t·d^-1 above Yanguan town and 5?20 t·d^-1 Haizhou street,the pollutant discharge reduction of 43.5%can be achieved through the supervision of 16.9%facilities.