하수슬러지를 이용한 생물담체의 개발 및 적용

Abstract

To present new way of sewage sludge recycling method, feasibility of making and using porous biological support media was investigated. Porous biological support media was made of sludge cake from sewage treatment plant and loess, clay. They were mixed in varying ratio and burnt in high temperature to ensure sufficient mechanical strength. The results obtained from experiments were summarized as follows : 1. It was evaluated that optimum mixing ratio of sewage sludge cake, loess and clay was 75 : 10 : 15 and optimum burning temperature was 950 ℃. Compressive strength, void ratio, water absolute and specific surface area were 39.36 ㎏/㎠, 66.3 %, 51.7 % and 8.364 ㎡/g, respectively. 2. It was calculated that about 2.3 ton of sludge cake can be used to produce 1 m3 of biological support media. In other words, 2.1 m3 of sludge can be consumed for producing 1 m3 of biological support media when considering specific gravity of sludge as 1.1 3. It can be evaluated that maximum microbial retain capacity of biological support media was 20 ㎎ of microorganism/g of support media and maximum MLSS concentration of reactor was about 10,000 ㎎/ℓ. Successful formation of biofilm on support media was observed through scanning electronic microscope. 4. Biological support media prepared in this experiments were applied as packing material in intermittently aerated biofilm process and feasibility of simultaneous removal of organic and nitrogen was evaluated. It was evaluated that optimum oxic/anoxic time ratio was 40 min/80 min under the operating conditions of 0.804 g COD/day and 0.174 g NH4+-N/day. COD and nitrogen removal efficiencies were 96 % and 72 %, respectively. 5. Pilot scale experiment was conducted using biological support media made in this experiment to testify the feasibility of applying this system as water reusing process by treating effluent of sewage treatment plant. Optimum surface filtrating velocity and surface organic loading rate were 7～13 ㎥/㎡-hr and 1.95 g BOD/㎡/day, respectively. It can be evaluated that effluent from sewage treatment plant can be treated successfully as reusing purpose if the height of packed bed is maintained higher than 1.0 m and applied surface organic loading rate is maintained lower than 2.0 g BOD/㎡-day. 6. Waste sludge from sewage treatment plant can be reused successfully by applying it as raw material of porous biological support media made of sludge cake, loess and clay. It can be concluded that porous biological support media prepared in this experiment can be applied wastewater treatment plant as promising packing material.