Study On Two-phase Integrated (TISTD) Sludge Thickening And Digestion Reactor For Treating Sewage Sludge

The problem of sewage sludge treatment is becoming more serious with the development of wastewater treatment. From the experience in wastewater trentment plant, sludge treatment is the key challenge keeping it running well. But the defects in the present anrobic technology such as low load, long HRT, high investment make it necessary to develop more efficient reactor. So a new reactor called Two-phase Integrated Thickening and Digestion Reactor (TISTD) was designed in this paper, and a pilot experiment was carried on to study the TISTD reactor.The TISTD reactor has 110L in capacity, with design sludge feeding rate 30%. Hydrodynamic experimental results showed that the flow pattern of outer chamber was close to plug flow, while the flow pattern of inner chamber was close to completely mixed flow.To startup TISTD, using 10% sludge feeding rate, under the condition of mid-temperature(33~37℃), 28 days later, the TISTD reactor was running reposefully.The operation performance were studied when the sludge feeding rate was 20%, 30%, 40%, 50% respectively. Results showed that the optimal sludge feeding rate was 30%, and the hydrolic rentention time was 3.33d. When the rate of water content of influent sludge, the ratio of VS/TS in the range of 99.43~99.69%, 0.62~0.77 respectively; the rate of water content and the ratio of VS/TS of effluent sludge was in the range 89.52%~93.51%, 0.21~0.28 respectively. The suspended solids in effluent water was in the range of 0.15~0.6g/L, while the output of biogas was not so good, with 1.2m3biogas/m3·sludge.However, the thickening and digestation effects of the TISTD were separately better than conventional gravitational thickening tank and anaerobic digestor.Two-phase integrated and the separation of acid-phase and methane-phase were achieced to a certain degree in the reactor indicated by the outputs of ph, VFA and Bicarbonate Alkalinity. Biofacies experiments illustrated that there were many kinds of anaerobic bacteria. The dominating bacteria were Methanococcous and Methanothric soehngenii. At the same time, dynamic model of the reactor treating sewage sludge was deduced according to the experimental date.