His team has 25 members, but only 13 go out for inspections while others handle logistics, communication and administration. Regulations require enterprises receiving complaints or citations to respond within two months of the day of complaint. The team tries to respond to every complaint within three days.

"Any resident's complaints, no matter how small, are a big deal for us," says Deng. "The sooner we act, the sooner the environment will improve."

Weixing Port in Nanhui after cleanup operation [Shanghaiwater.gov.cn]

Although the team puts in long hours, many residents still complain about perceived "inaction."

"We can understand their anxiety, but investigation requires time. We cannot simply shut down any enterprises the minute we receive a complaint," explains Deng.

Even after the team has collected evidence and illegal pollutants have been confirmed by a laboratory, it still takes time for the final sanction to be determined and carried out. It's usually a fine, an order to halt pollution and upgrade equipment - or face further fines and possible shutdown.

Since the team has no enforcement powers, it can only ask for a court order if an enterprise refuses to comply and clean up.

"In that case, it can take at least six months to carry out any sanction from the day we collected evidence," says Deng.

The conflict of interest between residents and workers in a polluting enterprise also makes it difficult to swiftly enforce a cleanup and sanctions.

"What can we do about workers if we suddenly shut their factory, and what about a factory with outstanding loans and orders not yet complete?" he asks.

Usually, the environmental protection department gives the polluting enterprise some time to clean up, before calling for a shutdown. Meantime, inspectors urge companies to improve production processes.

As more industrial zones are launched in Nanhui, there will be a lot more work for these environment cops.