[Experimental investigation of aerobic granule cultivation in high strength Vc wastewater]

Aerobic granular sludge was cultivated in sequencing batch reactors (SBRs) fed with high strength and refractory real Vc wastewater. In the reactor treated transformation residues, it was achieved a completely aerobic granulation, and the sludge was 0.2-1 mm in diameter, average settling velocity 31.2 m x h(-1). In another reactor treated refinery or extracted residue, partially granular formation was reached, and the sludge was 0.5-2.5 mm in diameter, average settling velocity 26.3 m x h(-1). The formation of good aerobic granules contributed a good operational property. When influent COD was 1,000-1,500 mg x L(-1), COD removal efficiency was maintained approximately 80%. It could be improved better by adding biodegradable organic matters in feed. Through microscopic observation of sludge from two different reactors, the protozoa and biodiversity of microorganisms in reactors were determined not only by the operational parameters, but also by the influent composition. The granulation process in the experiment was proceeded through three stages, i. e. sludge activation phase, acclimatization phase and aerobic granulation phase. In operation control, the settling-time was used as the key factor for the formation of aerobic granules, which could decant the flocculent sludge and regulate the organic loading, and eventually promote the granulation process.