This study was carried out to improve septic tank for piggery wastewater treatment of small pig farm. Septic tank were consisted of screen tank, aeration tank with two steps, settling tank, and filtering tank. Aeration tanks were filled with ALC of ø4~5cm. All operation steps were performed by timer from influent to effluent. Septic tank decreased BOD by 94.7% from 4,298.3mg/$ell$ to 226.3mg/$ell$ and also decreased SS by 92.4%, from 2,231.3mg/$ell$ to 161.0mg/$ell$, respectively.