Detailed investigation of bio-foam characteristics of piggery wastewater reveals long chain fatty acids-dominated foaming mechanisms

Abstract

Biological foam has seriously troubled the wastewater treatment process and brings significant challenges to effluent quality, process efficiency, and operation safety. This study systematically analyzed the characteristics of biological foam from three typical piggery wastewater treatment stations, identified the key substances causing biological foam, and revealed potential foaming mechanisms. Foaming characteristics evaluation indicated that, for piggery wastewater, the low surface tension (58.9– 69.7 mN·m−1) was the crucial factor leading to strong foaming capacity (r = −0.761), and high viscosity (0.24– 0.7 Pa·s) and zeta potential (−10.4 ∼ −15.3 mV) increased the foam stability (r = 0.857, −0.767, respectively). Multidimensional correlation analysis revealed that the long-chain fatty acids (LCFAs) in the influent of piggery wastewater were the key leading to the foaming issue, and their influences had two paths: the decrease of surface tension caused by LCFAs could directly induce a stronger foaming capacity (physicochemical path); moreover, LCFAs favored the enrichment of non-filamentous foam-related microbes (abundance >3.3 %) like Hydrogenophaga and Pseudomonas spp. to secrete more extracellular polymeric substances, increasing the viscosity and zeta potential to maintain the foam stability (biological paths). Based on the revealed foaming mechanism dominated by LCFAS, this study provided novel insight and valuable guidance for efficient and safe treatment of piggery wastewater.