Study On The Technology Of Controlling Initial Runoff Pollution In Farmyard

In recent years,rural urbanization in our country has developed rapidly,accompanied by an increase of hardening area in rural areas and gradually serious pollution of village non-point source,resulting in a series of water crises issues such as the continuous deterioration of the water environment,shortage of water resources,and destruction of aquatic ecosystems.Controlling of non-point source pollution in villages and improving village water environment are important aspects of the construction of sponge villages.Sponge village is built to distribute sources of polluted water and purify water quality through natural force drainage and low impact development?LID?technologies.Rainfall runoff in farmyard is an important source of pollution for the village's non-point source pollution.However,at present,there are few researches on the control of rural runoff pollution.The related achievements and project examples in our country and abroad point out that constructed wetland and rainwater retention pond have great potential in controling urban non-point source pollution.However,currently substrates used in constructed wetlands have problems such as high cost and poor nitrogen and phosphorus removal.New substrate was explored to enhance the purification ability of constructed wetlands and rainwater retention pond in this research.In this regard,some researchs were carried out such as monitoring water quality of rainfall runoff in farmyards,screening substrates,and the purification capacity of constructed wetlands and rainwater retention pond.The main conclusions were as follows:?1?Through monitoring the rainfall runoff water quality in Jiangshan village farmyard,it was found that among the four kinds of underlying surfaces,the runoff water quality of farmyard surface and vegetable fields was poor,and TN,TP,and SS were the main runoff pollutants.The scouring effect was obvious at the initial stage of the roof,yard surface,and track path flow,and the major pollution load was mainly concentrated within the runoff time of 1 h.?2?Through the static adsorption of nitrogen and phosphorus by substrates,the adsorption effects from high to low was:aerated concrete block?AAC?>dry sludge>gravel,with the theoretical saturated adsorption capacities of 1666.67,769.23,88.50 mg·kg^-1,respectively for ammonia nitrogen and 4170.71,2500.00,1000.00 mg·kg^-1,respectively for phosphorus.Therefore,AAC was preliminarily selected as the optimal substrate.?3?By investigating the purification effects of three constructed wetlands?filled with gravel,AAC,AAC+gravel?and a rainwater retention pond under different hydraulic load,it was found that AAC were more conducive to remove nitrogen and phosphorus in constructed wetlands than gravels.Among them,the removal effect of the three groups of wetland pollutants was greatly affected by the hydraulic load,but rainwater retention pond showed a stable and efficient treatment effect in comparison.I,II,and III wetlands had obvious characteristics of push-flow,but there were short-flow and stagnant areas,which reduced the utilization rate of the bed and caused the pollutant concentration fluctuated along the way.The internal mixing effect of IV retention pond was more obvious,and the actual residence time of wastewater was greater than the apparent residence time,which was more conducive to the removal of pollutants.?4?By studying the effects of rainwater retention pond at different intermittent operating times,it was found that the longer the interval between 1 and 7 days,the higher the removal rate of NH₄⁺-N and TN;longer intermittent operation was not conducive to the efficient removal of COD;with the prolonged operation of the system,the alkaline release effect of AAC weakened,and pH gradually decreased,which cuased TP removal rate decreased accordingly.?5?It was found through the simulated single-field rainfall test that the rainwater retention pond had a certain capacity of runoff regulation,and there was a certain delay in the emergence time of the peak discharge flow.The system's ability to reduce peak flow capacity under the pre-rainstorm rainfall type was stronger than that of medium-term heavy rain and late-rainstorm type,and the effluent water quality was stable,which had strong ability to withstand short-term shock loads.The simulated grey water treatment test found that the rainwater retention pond showed a good purification effect on the gray water quality.And the head loss of the system during this long-term operation was very little.For the initial runoff and grey water pollution of farmyards,natural power can be used to establish a non-dynamic runoff collection system,which can be comprehensively treated and reused with low-pollution grey water through the rainwater retention pond technology.