Case Story China

Treatment of pigment wastewater and generation of natural gas standard biomethane in Hangzhou, China

December 2021

Treatment of pigment wastewater
The biogas plant treating pigment wastewater is located in the Lily group, Qiantang industrial new area, Hangzhou, Zhejiang Province. It is a typical project for environmental protection in China’s coastal industry. The project was constructed in March 2021 and began operation in July 2021. It was developed, constructed (and is operated) by Beijing Huida Environmental Protection Technology Co., Ltd (Figure 1) at a total investment cost of 63 million yuan. The plant covers an area of 3.1 hectares and the facility can treat 4.5 million tonnes of sewage annually, reduce 11,250 tonnes of COD pollutants, and produce 2.7 million cubic meters of natural gas equivalant annually.

Treatment process and discharge standard
The composition of the pigment wastewater may be noted in Table 1. The wastewater is treated by 10 Upflow Anaerobic Sludge Bed (UASB) reactors with a volume of 1,500m3 per reactor under mesophilic conditions (Figure 2). The produced biogas is desulfurized (to maintain H2S below 10ppm) and upgraded (Figure 3). The upgraded biomethane is injected into the natural gas pipeline.