Influence of effluent-recirculation condition on the process performance of expanded granular sludge bed reactor for treating low strength wastewater

Abstract

A 2.0 L volume of EGSB reactor was operated at 20 degrees C for more than 500 days with 0.3-0.4 g COD/L of sucrose base wastewater to investigate the influence of effluent-recirculation on the process performance. At the start up period, the reactor was operated in EGSB mode with 5 m/h upflow velocity by continuous effluent recirculation. The COD loading was set to 7.2-9.6 kg COD/m(3) day with HRT of 1 hour. However, in this mode, EGSB reactor exhibited insufficient COD removal efficiency, i.e., 50-60%. Therefore, UASB mode (without recirculation, 0.7 m/h upflow velocity) was used for 30 minutes in every 40 minutes cycle to increase the COD concentration in the sludge bed. As a result, an excellent process performance was shown. The COD removal efficiency increased from 65% to 91% and the reactor could maintain a good physical property of retained sludge (sludge concentration: 33.4 g VSS/L and SVI: 25 mL/g VSS). Furthermore, retained sludge possessed sufficient level of methanogenic activity at 20 degrees C.

Tratamento de esgoto sanitário em um reator de leito expandido em escala plena, operado com regiões anaeróbia e aeróbia sobrepostas

“…As concentrações de nitrito e nitrato no efluente foram de 3,0 e 0,9 mg.L -1 , com taxa de carregamento igual 0,08 kgNKT.m -3 .dia -1 . Yoochatchaval et al (2008) estudaram um reator anaeróbio de leito expandido com volume de 2,0 L alimentado com esgoto sintético. O reator foi operado com velocidade ascensional de 5,0 m.h -1 , tempo de detenção hidráulica de 1,0 h e taxa de carregamento orgânico de 7,2 a 9,6 kgDQO.…”