Biological sludge reduction during abattoir wastewater treatment process using a sequencing batch aerobic system

Excess sludge disposal during biological treatment of wastewater is subject to numerous constraints, including social, health and regulatory factors. To reduce the amount of excess sludge, coupled processes involving different biological technologies are currently under taken. This work presents a laboratory scale sequencing batch aerobic system included an anaerobic zone for biomass synchronization (SBAAS: sequencing batch aerobic anaerobic system). This system was adopted to reduce sludge production during abattoir wastewater (AW) treatment. The average chemical oxygen demand (COD) removal efficiency of 89% was obtained at a hydraulic retention time (HRT) and a sludge retention time (SRT) of 2 days and 15-20 days, respectively. The comparison of SBAAS performances with a conventional sequencing batch activated sludge system (SBASS) found that the observed biomass production yield (Y(obs)) were in the ranges of 0.26 and 0.7 g suspended solids g(-1) COD removed, respectively. A significant reduction in the excess biomass production of 63% was observed by using the SBAAS. In fact, in the anaerobic zone microorganisms consume the intracellular stocks of energy by endogenous metabolism, which limits biosynthesis and accelerates sludge decay. The single strand conformation polymorphism (SSCP) method was used to study the dynamic and the diversity of bacterial communities. Results showed a significant change in the population structure by including the anaerobic stage in the process, and revealed clearly that the sludge production yield can be correlated with the bacterial communities present in the system.