| The urban river,which has a close relationship with the development of cities,is one of the important compositions in urban morphology.However,urban river ecosystems have been destroyed dramatically in the last few years.The restoration of urban rivers thus has significant meanings in many aspects like maintaining the benign motion of cities,etc.To make the rive flow meet the river ecological water requirement?REWR?is one of key points in the urban river restoration,since in which REWR is the most important predictor.The Kuxi River,as the primary tributaries of the Yangtze River,is related to the vitality of Jiangnan area?Chongqing,China?.Besides,the water quality of Kuxi River has a significant impact on the Yangtze River water bodies.Therefore,the study of current water environment and ecological water supply of Kuxi River is urgent and also has significant meanings.In this work,the current water environment pollution of Kuxi River was assessed according to data that were achieved by monitoring the water quality in relative monitoring sections.According to the study results of the current water environment pollution of Kuxi River,the water remediation approach was determined,and the ecological water supplement technique based on sewage resources was put forward.Further discussion was then made in combination with the actual water body.The ecological water supplement was determined,based on the limit of water resources development.What's more,the performance of current ecological treatment systems in Kuxi River was studied according to the data achieved by monitoring water quality.Meanwhile,the water quality of tail water was investigated.Then the water supply scheme was determined,whose effect was assessed by One Dimensional Water Quality Model.The results obtained in this study revealed that:?1?Some sewage directly discharged into Kuxi River because existing drainage network was imperfect.The drain was more in Kuxi River Basin,and the water quality was poorer at the drain.The water environment quality was assessed by the synthetical pollution index method,and results revealed the water quality of Kuxi River was medially polluted.And the synthetical pollution index was declining years,water pollution was more serious during drought period.The main indicators affecting the water quality of the Kuxi River were assessed by using principal component analysis?PCA?and with the aid of the SPSS software.Five main factors,BOD5,TN,TP,Fecal coli group and anionic surfaceactive agent were chosen as the main influence factor.The comprehensive pollution index rose with an obvious fluctuation.?2?The space pollution characteristics of the Kuxi River was assessed by using the comprehensive pollution index method through the data sampled of 11 monitoring sections?S1-1,S1-2,S2-1,S2-2,S3-1,S4-1,S4-2,S5-1,S5-2,S6-1,S7-1?.According to the results,the comprehensive pollution index first increased and then decreased,and the pollution degree of the downstream was higher than the upstream,but after the ecological treatment facilities the pollution index decreased obviously.Because pollution sources plunge into the river at section S2-2,S5-1,S5-2 and S6-1,the section pollution load is larger,with specific values being 0.12,0.14,0.14 and 0.12 respectively.The water pollution is more serious.?3?Based on minimum ecological base flow,the ecological water demand of Kuxi River was calculated,and the value was 22.99 million m3/a,with 4.74 million m3/a of off-stream ecological-water demand,5.84 million m3/a of in-stream ecological-water demand,0.66 million m3/a of sediment transport ecological-water demand,7.65 million m3/a of water demand in city rivers and lakes and 0.41 million m3/a of water demand to water pollution dilution.Ecological water demand accounted for 65.82% of the average annual runoff.?4?When the tail water from Chayuan sewage plant played as the supply water source,its water quality could meet the standard type of bad ?.Besides,these indexes such as TP,BOD5,TN,etc,were beyond the range of the standard type of ?.Through the potency analysis of the current ecological treatment systems in the reach of Kuxi River,the present wetlands had certain treatment effects to the COD and BOD5 of the hydrating water,with removal rate of 3.6% and 20% respectively.But the TP and NH3-N removal effect is not obvious.The research results showed that existing wetland need to be rebuilt and maintenance and management need to be strengthened to ensure its processing effect,if the tail water of the sewage plant need depth processing.?5?The water environmental capacity was calculated by complete mixing method,in which four pollution indexes,CODMn,BOD5,NH3-N and TP,were chosen.The corresponding water environmental capacity was 147.65,141.05,6.36 and 2.04 t/a respectively.According to the review analysis,the tail water had the potential to work as the source of water in the ecological water supplement project of the Kuxi River.?6?According to the limit development of surface water to supply water,the ecological-water demand of Kuxi River was 9.02 million m3/a.The tail water could be used as the source of water in the ecological water supplement project of the Kuxi River during the basin water season?From October to April?.The water supply scheme of Chayuan sewage plant was determined comparatively,whose performance was assessed by NH3-N,TP,BOD5 through Zero/One Dimensional Water Quality Model.After sail water was supplied,the NH3-N,TP and BOD5 concentration of the section S1-1 had manifested an obvious upward trend with the increase rate of 36.8%,while the section S7-1 manifested an obvious down trend,falling by 9.1%.According to the results of water quality model simulation,the water quality of each section water quality could meet the standard type of ? of the surface water standard after ecological water supplement.Meanwhile,the effect of supplement with tail water was simulated with the sewage along river being completely intercepted,and the result showed that the concentration of NH3-N,TP and BOD5 was reduced by 25%,15% and 27.4%,respectively.Compared to the condition before sewage interception,moisturizing effect is further enhanced.However,based on the view of prevention of water eutrophication,the nitrogen and phosphorus nutrients should be deeply treated before using for ecological water supplement.With the purpose of combining wastewater-reuse with river ecological restoration,that tail water from wastewater plant plays the role of supply source was investigated in the work presented in this paper,which could provide practical value for wastewater-reuse,as well as ecological water supplement. |
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