Research on optimization of initial rainwater interception capacity of sponge-type rainwater inlet

An assembly-type optional sewage-interception rainwater inlet was proposed, with geotextile, stainless steel screen and five different fillers as the filter modules, and the artificial simulated rainwater was equipped for the test to study its removal effect on the pollutants of suspended solids (SS), chemical oxygen demand (COD), ammonia nitrogen (NH₄ ⁺-N), total nitrogen (TN) and total phosphorus (TP), in the initial rainwater under different sewage intercepting devices. Its ability to reduce the initial runoff pollution was tested and the feasibility and economy in practical engineering applications were evaluated. The test results showed that: in the geotextile and stainless steel screen filter modules, geotextile had a good removal effect on SS, while the stainless steel screen had an obvious removal effect on SS when the aperture was decreased to 0.074 mm, but the two filter modules had poor removal effect on COD, NH₄ ⁺-N, TN and TP. The five filtration modules with high furnace ash coke particles, activated zeolite, coconut shell biochar, ceramsite and activated carbon as filter materials, could effectively improve the removal effects of COD, NH₄ ⁺-N, TN and TP in the initial rainwater. Among them, ceramsite could not only achieve the ideal removal effect of nitrogen and phosphorus, but also achieve good removal effect on SS and COD. Its service life was comparable with other filtration modules, and the market unit price (5-13 yuan/kg) was slightly lower than other filtration modules .