Spontaneous granulation of moderately halophilic sludge inoculated with saltern sediments from single granule into multi-granule aggregation

Abstract

There is very limited research on the application of moderate halophiles for biotreatment of hypersaline wastewater widely generated from some industries. This study demonstrated the development of moderate halophiles inoculated from saltern sediments into aerobic granule sludge (AGS) to treat hypersaline wastewater with a salinity of 100 g/L. The granulation of moderate halophiles can occur without applying the settling velocity selective pressure. The saltern sediment initially aggregated into single small granules and finally developed into 1200 ± 50 μm multiparticle granules. The halophiles affiliated in Halomonas was dominant in the granular bacterial community, with a relative abundance of 94.52%. Halomonas ventosae secreted sulfated polysaccharides. The sulfated polysaccharides content accounted for 63.95 ± 2.10% in the polysaccharides (PS), having an adhesive role in connecting single granules. Multiparticle granules showed the clear stratified structure, with α-D-glucopyranose polysaccharides in the inner bounders and β-D-glucopyranose polysaccharides in the outer. The moderately granular sludge showed the stable chemical oxygen demand (COD) removal efficiency of >90% and the aerobic total inorganic nitrogen (TIN) removal efficiency (equal to ammonia removal) of 70 ± 5.00%. This paper contributes new insight into the formation of moderately halophilic granular sludge and accelerates the application of moderately halophilic granular sludge to treat hypersaline wastewater.

Keywords: Halomonas sp; Hypersaline wastewater; Moderately halophilic granular sludge; Saltern sediments; Sulfated polysaccharides.