Study On The Application Of Constructed Rapid Infiltration Technology In The Treatment Of Rural Domestic Sewage

The use of rural domestic sewage for farmland irrigation after treatment can effectively alleviate the shortage of water resources,and promote agricultural production and improve the ecological environment.In recent years,the penetration rate of domestic and foreign sewage irrigation has increasing year by year,however,there are certain problems in irrigating the sewage without any treatment,and scientific agricultural irrigation must be put on the agenda.In view of the lack of capital in the construction,operation and maintenance of sewage treatment facilities and the shortage of management and operation experience in rural areas of China,it is not appropriate to choose urban sewage reuse technology,and it is advisable to choose the land sewage treatment and reuse technologies for rural domestic sewage,which are not expensive,and has lower demand in construction and later operations and maintenance.In this study,three sets of CRI?low-column,high-column,ventilation-column?are used for comparison.By rationally designing the structure of the CRI device,the enhancement of removal on nitrogen and phosphorus is changed to retain nitrogen and phosphorus,we take advantage of the poor removal effect of nitrogen and phosphorus by CRI,through the adjustment of operating parameters,the removal of pollutants in sewage can be achieved while retaining the maximum nitrogen and phosphorus elements.The main research contents and results are as follows:?1?In order to screen the suitable fillers to retain nitrogen and phosphorus,the adsorption and desorption characteristics and physical and chemical properties of clay ceramsite,shale ceramsite,local fine sand and local coarse sand are studied.The results show that clay ceramsite and coarse sand have poor adsorption of nitrogen and phosphorus and high desorption rate,and the porosity and permeability coefficient are large,and it is not easy to make block.Therefore,clay ceramsite and coarse sand are selected as CRI fillers.?2?Using the"continuous water inlet fast film hanging method"to start the CRI system,the results show that the low-column and the high-column were successfully started on the33th day,and the ventilation-column was successfully started on the 27th day.And the thickness of the filler has no obvious effect on the speed of the CRI system to complete the work,and mechanical ventilation shortens the start-up time of the CRI.After the start-up is successful,the removal rate of COD of the three groups of CRI is stable at more than 60%.?3?Three sets of CRI?low-column,high-column,ventilation-column?are used for comparison,in order to study the effect of filler thickness and mechanical ventilation on domestic sewage treatment under different the wet-dry ratios?continuous inflow,3:1,1:1,1:3?.The results show that under the four wet-dry ratios,the low-column and high-column have the highest removal rate of COD and SS when the wet-dry ratio is 1:1,and the ventilation-column has the highest removal rate of COD and SS when continuous water is fed.Under these four wet-dry ratios,the three groups of CRI have better retention effect on TN,with an average removal rate of 9.43%?25.8%,but the retention effect on TP is relatively poor,with an average removal rate of 60.78%?82.79%.?4?Three sets of CRI?low-column,high-column,ventilation-column?are used for comparison,in order to study the effect of filler thickness and mechanical ventilation on domestic sewage treatment under different hydraulic loads?1 m³/?m²·d?,1.25 m³/?m²·d?,1.5m³/?m²·d??.The results show that under the three hydraulic loads,the three groups of CRI have the best removal of COD and SS at the hydraulic load of 1m³/?m²·d?.Under these three hydraulic loads,the three groups of CRI have a better retention effect on TN,the average removal rate is 11.43%?18.89%,but the retention effect on TP is relatively poor,the average removal rate is 38.37%?67.86%.?5?Three groups of CRI?low-column,high-column,ventilation-column?are used for comparison,in order to study the effect of filler thickness and mechanical ventilation on domestic sewage treatment under different influent COD loads?70mg/L,100mg/L,225mg/L?.The results show that the removal of COD and SS by the three groups of CRI increase steadily as the COD concentration in the influent increases.The low-column can irrigate raw vegetables between 70 mg/L and 100 mg/L.When the influent COD concentration is about225mg/L,the effluent can only irrigate non-raw food vegetables;the high-column and the ventilating-column can irrigate raw food vegetables under the three influent COD concentrations.And under these three influent COD concentrations,the three groups of CRI have better retention effect on nitrogen,the average removal rate of TN is up to 33.44%,and the retention effect is better when the influent COD concentration was lower;the retention effect on phosphorus is relatively poor,and the low-column had a better effect on TP.Its average removal rate is about 50%,and that of TP by high-column and ventilation-column is about 70%.?6?Under the best working conditions,the removal effect of three sets of CRI on the basic control indicators required by agricultural irrigation standards and the retention effect of nitrogen and phosphorus were studied,and the surface morphology of the filler at different heights after 35 days of stable operation were analyzed.The results show that the 35-day stable operation of the three groups of CRI effluent pH values is stable.The effluent BOD₅,COD,SS,LAS,total salt content,chloride and five heavy metals?hexavalent chromium,lead,cadmium,Mercury and total arsenic?meet the raw food vegetable standard in the"Farmland Irrigation Water Quality Standards?GB5084-2005?",DOM is significantly removed by the three groups of CRI biodegradation;the retention effect of the three groups of CRI on phosphorus:low-column>high-column>Ventilation-column,the retention effect on TN is high-column>low-column>Ventilation-column;the number of coliform bacteria in the three groups of CRI influent manure exceeds 110 times the standard of agricultural irrigation,and the effluent after treatment is far lower than the standard of raw food vegetables;After the stable operation of the three groups of CRI,according to the SEM scanning electron microscopy,packing surfaces showed that from the upper surface of the packing layer to the bottom,the biofilms in the CRI column decrease in turn,and the biofilms on the surface of the lower packing are sparse and porous.