Comparing the effect of bioflocculant with synthetic polymers on enhancing granulation in UASB reactors for low-strength wastewater treatment

Abstract

This study was aimed at introducing a novel bioflocculant to enhance anaerobic granulation in a UASB reactor for lowstrength
synthetic wastewater and comparing the effect with synthetic polymers. A laboratory-scale study was undertaken to
achieve this goal. Four identical UASB reactors were operated in parallel in the treatment of low-strength synthetic wastewater
over 136d at 35 ± 1 ℃. One unit (labelled R1) was injected weekly with bioflocculant, a 2nd unit (labelled R2) was operated
with the addition of acrylamide-chitosan graft copolymer, a 3rd unit (labelled R3) was operated with the addition of cationic
polyacrylamide, and a 4th (labelled R4) served as a control without any polymer addition. The results showed that R1 was
the most efficient, while R3 performed better than the other two reactors. The rates of granulation in R1, R2 and R3 were
enhanced by 50% vs. 87% vs. 75% when compared with R4. Though bioflocculant addition was not the most effective way
of developing large-size granules, it was demonstrated to be the least inhibitory in enhancing micro-organism multiplication
and improving microbial metabolic activity. The volatile suspended solids to suspended solids ratio and the sludge methanogenic
activity of the granular samples from R1 were higher than those of the other three reactors. When compared with the
control reactor, polymer-added reactors performed better at the most organic loading rate as polymer addition resulted in a
considerably higher degree of retention of biomass and lower solids washout from UASB reactors. Granulation was achieved
in all four of the reactors, but the granules from polymer-enhanced reactors appeared earlier and were larger than those from
the control reactor were.

Water SA Vol. 31 (2) 2005: pp.177-182