Waste activated sludge derived biopolymer amelioration for desert sand: Impact on moisture retention, vegetation growth and microbial community

초록

Extracellular polymeric substances (EPS) are complex, high molecular-weight polymer mixtures secreted by microorganisms involved in organic matter degradation during the activated sludge wastewater treatment process. In this study, EPS extracted from wasted activated sludge (WAS) was used as a material to assess improvement in moisture retention and fertility of desert sand. Compared to untreated sand (30.87%), the water retention capacity of sand treated with 0.1% EPS increased to 75.51%, representing approximately 2.4 times enhancement. Pot experiments revealed that EPS addition promoted ryegrass growth: plant height increased up to 93.70%, shoot fresh weight increased up to 304.36%, and chlorophyll content increased up to 94.68% relative to the CK group. Metabolomics analysis indicated that EPS induced pronounced metabolic changes in ryegrass root exudates, with 44 shared DEMs (38.26%) identified between the two comparison groups. EPS addition significantly enriched Glycerophospholipid metabolism pathway, facilitating rapid cell division and improving antioxidant defense mechanisms. The dominant microbial genera of 0.1% EPS group were Stutzerimonas (12.75%) and Pseudomonas (10.87%), which are popular soil probiotics that participate in the nitrogen cycle. The yield of EPS extracted from WAS achieved 0.25 kg EPS/kg SS. Moreover, the economic evaluation results indicate that the EPS extraction cost in this study was 0.58 USD/kg EPS, which is substantially lower than the current market price of Xanthan gum (1.50-4.00 USD/kg). In general, the present study suggested that EPS extracted from WAS could be applied as a potential sand amelioration agent for improving moisture retention and fertility of desert sand.

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