Multi-media-layering system for food service wastewater treatment

Abstract

Domestic wastewater treatment was studied using the Multi-Media-Layering (MML) system. There are two MML units in the system for alternative use. Each unit has 1.0×2.0×1.5 m internal dimensions. One unit is composed of soil mixed with sawdust plus iron scraps at a ratio of 75:10:15 by weight; the other is composed of soil mixed with (kenaf plus corncob) plus iron scraps at the same ratio as the first unit. The mixture layers are arranged in a ‘brick like’ pattern. Each block is 0.08 m thick and filled in a concrete box. Charcoal of 0.02 or 0.03 m thickness was put on the top of the mixture layer. Zeolite was inserted between the blocks (0.05 m thick) to prevent clogging. Air is supplied through porous pipes installed at the middle layer of the MML unit. The system was tested using toilet wastewater from Kasetsart University’s cafeteria. For this experiment, the wastewater was discharged to the two concrete boxes simultaneously about 460 l day −1. The wastewater and treated water were collected every 2 weeks for chemical analysis. The results revealed that the removal percentage of suspended solid, biochemical oxygen demand (BOD), chemical oxygen demand (COD), total N, NH 4-N, total P and dissolved P were 53, 48, 58, 68, 53, 52 and 64, respectively for a media mixture of sawdust plus iron scraps. When aeration was applied for 24 h, at 50 l min −1 for 14 days, the efficiency of wastewater treatment increased significantly. The percentage removal of suspended solid, BOD, COD, total N, NH 4-N, total P and dissolved P was 71, 90, 70, 91, 76, 90 and 89 by sawdust with a loading rate of 230 l m −2 day −1. Kenaf plus corncob was less effective compared to sawdust. Aeration assists decomposition of BOD, COD and suspended solid as well as phosphate fixation. The MML system was more effective than the current system used at the Department of Soil Science.