No abstract

The first full-scale semi-centralized wastewater treatment and resource recovery system based on source separation was implemented from 2014. To assess the operation performance, operating costs and resolve the problems faced in this system, the latest operation data from April 2017 to September 2018 was investigated. The results show that greywater and blackwater modules exhibited good removal performance for organics and nutrients, although misconnection between pipelines existed and influent loading rates fluctuated. The effluent could meet reuse standards. The biogas production rates of raw sludge could reach 7.27–10.9 m3 gas·per cubic raw sludge. The specific cost of treated water was higher than in a conventional treatment system. Power consumption made a major contribution to the total cost with a proportion of 55.3%–94.2%. After optimizing and considering the comprehensive efficiencies, the costs would be affordable. The dewatered sludge of the anaerobic digestion module has been applied to agricultural and landscaping soil. It is suggested that organics in blackwater could be recovered as volatile fatty acids with high-efficiency anaerobic fermentation and used as an external carbon source for short-cut biological nitrogen removal. In conclusion, the semi-centralized system will be a feasible and sustainable alternative for conventional treatment systems in future.

Blackwater has more benefits for carbon recovery than conventional domestic wastewater. Carbon capture and up-concentration are crucial prerequisites for carbon recovery from blackwater, the same as domestic wastewater. Both chemical enhanced primary treatment (CEPT) and high-rate activated sludge (HRAS) processes have enormous potential to capture organics. However, single CEPT is subject to the disruption of influent sulfide, and single HRAS has insufficient flocculation capacity. As a result, their carbon capture efficiencies are low. By combining CEPT and HRAS with chemical enhanced high rate activated sludge (CEHRAS) process, the limitations of single CEPT and single HRAS offset each other. The carbon mineralization efficiency was significantly influenced by SRT rather than iron salt dosage. An iron dosage significantly decreased chemical oxygen demand (COD) lost in effluent. Both SRT and iron dosage had a significant influence on the carbon capture efficiency. However, HRT had no great impact on the organic mass balance. CEHRAS allowed up to 78.2% of carbon capture efficiency under the best conditions. The results of techno-economic analysis show that decreasing the iron salt dosage to 10 mg Fe/L could promise profiting for blackwater treatment. In conclusion, CEHRAS is a more appropriate technology to capture carbon in blackwater.