Consequences of manure filtration through pervious concrete during simulated rainfall events

Agricultural activities, and in particular those associated with animal production facilities, can adversely affect water quality. Pollution in runoff from these facilities includes sediments, pathogens, and nutrients. Pervious concrete is a type of concrete made by eliminating a large portion of the fine aggregate (or sand) in the concrete mix. This allows interconnected void spaces to be formed in the hardened concrete which have the ability to allow water to permeate at relatively high rates. Pervious concrete is a material that is being increasingly utilised in urban areas for runoff and stormwater reduction following rain. Pervious concrete also has been shown to have the potential to improve water quality as stormwater or wastewater passes through the concrete matrix. Weekly rainfall simulations were conducted after manure was applied to the surface of pervious concrete specimens. The effluent passing through the manure and pervious concrete was tested for dissolved organic carbon (DOC), ammonium, nitrate, nitrite, total nitrogen (TN), soluble phosphorus (SP), and total phosphorus (TP). Statistical analyses indicated significant increases and decreases in most of these analyte concentrations following simulated rain. The highest concentrations of some analytes (nitrate, TN and TP) in the effluent occurred after the first rainfall simulation. Maximum concentrations for other analytes (DOC, ammonium, nitrate, and SP) occurred after subsequent rain events. There was a significant decrease in faecal coliform concentration as 35.8% passed through after the initial addition of manure and less than 0.2% passed through after two subsequent rainfall events. The use of different aggregates or additives in the pervious concrete mixtures did not significantly affect nutrient concentrations or faecal coliforms in the effluent from the manure. Carbon dioxide emissions indicated microbial activity in which immobilisation of nutrients and decomposition of the manure could occur. Therefore, the potential exists for additional nutrients to be retained by microorganisms in animal waste deposited on the pervious concrete surface.