Micropollutant Removal from Laundry Wastewater in Algal-Activated Sludge Systems: Microbial Studies

The main objective of this research was to study the feasibility of using algal and algal-activated sludge systems in treating laundry wastewater. Three different types of systems-green microalgae (system A), diatoms + activated sludge (system B), and green microalgae + activated sludge (system C)-were studied at six different solid retention times (SRT)-6, 8, 10, 12, 14, and 16 days-to evaluate their performance in removal of total organic carbon (TOC), total nitrogen (TN), anionic surfactants, and micropollutants with added trace elements. System B showed relatively better performance in removal of TOC (79%) and TN (90%). A total of 64 compounds were detected in influent when analyzed by LC-MS, of which 19 were grouped under herbicides, pesticides, and insecticides, 25 under pharmaceuticals, and 20 under others. Linear alkylbenzene sulfonate (LAS) was detected only in the effluent of system A and was not detected in both system B and system C. Grotan OX, an anti-microbial, was the compound with least removal in all the systems. The bacterial LAS degrader/tolerant plate count in system B at 16-day SRT was 2000 CFU/mL, 50 times more than the plate count of system C (40 CFU/mL). The LAS degrader/tolerant bacterial species identified were Aeromonas caviae and Klebsiella pneumonia in both systems B and C. The LAS degrader/tolerant green microalgae plate count at 16-day SRT was 130 CFU/mL, whereas no LAS degrader/tolerant diatom colonies were observed. Graphical Abstract