Academic researchers in China have combined chemically enhanced primary sedimentation (CEPS) of sewage with acidogenic fermentation of sludge to enhance removal of conventional and emerging wastewater contaminants of concern. The tandem process was demonstrated effective in eliminating retinoids and Schematic of the wastewater treatment system. Source: University of Hong Kongestrogenic endocrine disrupting chemicals from sewage and sludge.

Analysis of wastewater and sludge sampled during different treatment stages at three conventional treatment facilities in Hong Kong showed average removals of 57% of retinoids and 54% of estrogenic agents. Laboratory tests next showed increased removal efficiencies with the new tandem treatment scheme. Aluminum-based CEPS eliminated 65% of retinoids and 73% of estrogenic contaminants from sewage, while 80% of retinoids and 72% of estrogens were removed after iron-based CEPS.

Acidogenic fermentation of the CEPS sludge resulted in further removal of 50% and 58% of retinoids, and 50% and 47% of estrogenic pollutants in the supernatants of Al-sludge and Fe-sludge, respectively.

Economic gains accompany the improved treatment efficiencies of the process. The cost of CEPS for wastewater treatment is less than a half of that of secondary wastewater treatment schemes. Recovery of organic carbon and phosphate resources from the sludge in the acidogenic fermentation phase for future use in carbon fiber and fertilizer production, respectively, also underscores the economic attractiveness of the technology.

A pilot wastewater treatment system incorporating the treatment process developed by researchers from University of Hong Kong, Tsinghua University and City University of Hong Kong is under construction in Shenzhen.