Discover China: Hometown of "zhacai" pickles tests water in wastewater treatment

24-06-2020
wastewater treatment,water treatment,China

Authorities in southwest China's Chongqing Municipality are using modern facilities to treat wastewater from "zhacai," a traditional Chinese pickles made from mustard stems.

In the township of Baisheng in Fuling District, Erciyan, a rural cooperative specialising in making pickles, ferments up to 500 tonnes of mustard stems a year. Mustard stems are the raw materials for making zhacai.

The cooperative has helped 24 local impoverished families cast off poverty, but about 100 tonnes of wastewater from the pickling process proved to be a big headache for Liu Hui, who is in charge of the cooperative.

"In the past, most of the wastewater was discharged without treatment, which polluted the environment," Liu said.

However, thanks to a new modern wastewater treatment network, the wastewater is now collectively discharged to a local plant for treatment, greatly reducing the amount of environmental pollution.

Hometown of zhacai
Fuling District is located along the Yangtze, China's longest river. The district is the birthplace of zhacai, known as the "national appetiser" among the Chinese public.

The delicacy is believed to have originated in Fuling during the Qing Dynasty (1644-1911). Locals salt the stems and coat them with chilli sauce. The stems are then fermented in jars before they are ready for sale.

Fuling produces large quantities of zhacai, with 37 companies making the pickled mustard stems in the district. The companies can produce more than 600,000 tonnes of zhacai annually, with an annual revenue of about 5 billion yuan (about 707 million U.S. dollars).

This year, the district's yield of mustard stems has exceeded 1.6 million tonnes, increasing the income of more than 600,000 local farmers.

However, the industry's development also comes with a price. The salting and processing of zhacai produces a huge amount of wastewater.

In the village of Zizhu, for example, factories and individual zhacai makers used to discharge wastewater directly into the environment.

"The wastewater was not treated and was discharged into rivers, which caused the rivers to become black and smelly," said village official Wang Shichuan. "The wastewater also eroded the village farmland."

Zhacai wastewater is high in salt, nitrogen and phosphorus, making it very difficult to treat.

The amount of zhacai wastewater in Fuling is about 2 million tonnes a year. If not treated properly, it could threaten the ecology of the Yangtze River, said Zhao Liming, deputy head of the district bureau of ecology and environment.

Testing waters
To prevent water pollution, Fuling authorities began testing waters in the treatment of zhacai wastewater in 2000.

The first wastewater processing station was established in 2008, and the treatment method was later introduced to various zhacai-making companies.

In the Baiheliang factory of Chongqing Fuling Zhacai Group Co., Ltd., dark-colored, smelly wastewater goes through a complicated process of dephosphorisation, hydrolytic acidification, anaerobism and a cyclic activated sludge system before being discharged.

The water treatment facility, built in 2012, cost more than 20 million yuan and can handle 1,600 tonnes of wastewater on a daily basis, said Lyu Kangquan, head of the group's safety and environmental protection department.

Fuling has about 2,000 individual zhacai makers who provide fermented stems to the companies. These individuals also produce a considerable amount of wastewater.

Local authorities have demanded that these individual makers build wastewater storage facilities, and companies that purchase the fermented stems from them are required to transport and treat the wastewater on their behalf. Joint patrols are conducted to enhance supervision.

Authorities also built wastewater treatment plants in areas where the companies and the individual makers converge.

The wastewater treatment plant in the township of Baisheng, for instance, handles more than 1,200 tonnes of wastewater from nine companies and about 100 individual makers who ferment the stems in the vicinity.

Treatment techniques have been improving in the past few years, and the district is still exploring ways to perfect the treatment process, according to Zhao Liming, a local ecology and environment official.

Last year, Chongqing Fuling Zhacai Group Co., Ltd. implemented a new treatment technique, which can handle 220 tonnes of wastewater and recycle about 16 tonnes of salt from the water a day.

Meanwhile, authorities are encouraging zhacai makers to use the high-intensity saltwater to make soy sauce. Currently, Fuling's zhacai soy sauce production stands at about 50,000 tonnes a year.

The district has spent more than 100 million yuan in treating zhacai wastewater so far, and all the zhacai companies in Fuling have installed treatment facilities.

"Only when we learn to protect the lucid waters and lush mountains can we truly have sustainable development in the zhacai industry," said Liu Hui, head of the cooperative.