Analysis Of Pollution Status Of Yihong River System In Dongying And Design Of Artificial Subsurface Wetland

The Yihong River system in Dongying City,Shandong Province,has been polluted as a typical black and odorous river channel.The municipal government has formulated the ecological management of“endogenous treatment+construction of ecological river channel+Yihong River wetland+monitoring operation+Guangbei reservoir water diversion”.Through the treatment of the spillway and its main tributaries,the environmental quality of the water body can be significantly improved,so that the water quality in the river channel will fully meet the Class V water quality standard in the Surface Water Environmental Quality Standard,and the black and odorous water body will be eliminated.In this paper,the water quality and quantity changes along the Yihong River are obtained through investigation and sampling along the river channel,and the main pollution sources causing the black odor of the Yihong River are analyzed.The upper reaches of the Yihong River are mainly polluted by Cuijia Village.The middle reaches are polluted by the direct discharge of domestic wastewater formed by the overflow of the sewage pipe network in Kenli County and the high concentration ammonia nitrogen wastewater from the six dry rows.The downstream is mainly polluted by the aquaculture wastewater.The effect of artificial subsurface wetland on the water treatment of the Yihong River was demonstrated by experiments.The effects of the ratio of gravel and zeolite in the matrix and the hydraulic retention time?HRT?on the treatment effect of constructed wetland were studied,which was suitable for the design of artificial subsurface wetland.The matrix ratio and hydraulic retention time complete the engineering design of the artificial subsurface wetland of the spillway.It has been found that an increase in the proportion of zeolite in the matrix reduces the COD treatment efficiency,but greatly improves the removal of NH₄⁺-N and TN.The most cost-effective matrix ratio is 20%zeolite and 80%gravel.Longer HRT has a good help to remove COD and TN from constructed wetlands.However,due to the limited dissolved oxygen content,longer hydraulic retention time will not help the removal of NH₄⁺-N.The suitable HRT for Yihong River constructed wetland is 18 h.The artificial flooding wetland of the Yihong River consists of a pre-treatment pond,a lifting pump station,and a subsurface flow wetland.The primary and secondary subsurface wetlands have a total area of 241,000 m²,and the matrix consists of 20%zeolite and 80%gravel with a total residence time of 18 h.When the water quality of the Yihong River reaches the influent standard,it is upgraded to the pre-treatment pond through the lifting pump station.The effluent from the pre-treatment pond flows through the first-order subsurface wetland and the second-order subsurface wetland,and finally merges with the effluent from the ecological filter bed to enter the surface-flow constructed wetland.The water output index reaches the surface water class V water quality standard.