Key function of Kouleothrix in stable formation of filamentous aerobic granular sludge at low superficial gas velocity with polymeric substrates.

Forming and maintaining stable aerobic granular sludge (AGS) at a low superficial gas velocity (SGV) is challenging, particularly with polymeric substrates. This study cultivated filamentous aerobic granular sludge (FAGS) with filamentous Kouleothrix (Type 1851) at low SGV (0.15 cm/s) utilizing mixed acetate-soluble starch. Within approximately 260 days, notable increases in the relative abundance of Kouleothrix (from 4 % to 10 %) and Ca. Competibacter (from 1 % to 26 %) were observed through 16S rRNA gene analysis. Metagenomic analysis revealed increased expression of functional genes involved in volatile fatty acid (VFA) production (e.g., ackA and pta) and polyhydroxyalkanoate synthesis (e.g., phbB and phbC). Kouleothrix acted as a skeleton for bacterial attachment and was the key fermenting bacteria promoting granulation and maintaining granule stability. This study provides insight into the formation of FAGS with low-energy and non-VFA substrates.

Adsorption of Cu (II)and Co (II) from aqueous solution using lignosulfonate/chitosan adsorbent.

In practical application, the adsorption capacity, adsorption kinetics, recycling and production cost of adsorbent affect the application of adsorbent. In this study, porous lignosulfonate/chitosan adsorbent was prepared by simple radical polymerization of acrylic acid in the mixed solution of lignosulfonate and chitosan. The porous and large surface area of adsorbent provides more adsorption sites for heavy metal ions. A variety of characterization methods were used to characterize the appearance and structure of the adsorbent. Adsorbent can effectively adsorb heavy metal ions in aqueous solution, and has the best removal effect for Cu2+ and Co2+. The adsorption capacity of adsorbent for Co2+ is 386 mg g-1, and for Cu2+ is 283 mg g-1. 0.01 g adsorbent was used to adsorb 100 mg L-1 Cu2+, and the adsorption equilibrium was reached within 60 min. When the amount of adsorbent reaches 0.03 g, the removal rate of heavy metal ions of 100 mg L-1 can reach 99%. In this study, an adsorbent based on acrylic resin was developed.