Cānguǎn de shàoshuǐ yào jiāogěi zhuānmén de gōngsī chǔlǐ, bù néng suíbiàn dàodiào.
Restaurants have to hand their swill over to a specialist company; they can't just pour it away.
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潲水 is the southern word, used in Guangdong, Guangxi, Hunan and Sichuan. The standard word is 泔水.
culture
Oil illegally skimmed from restaurant swill and drains and resold for cooking is called 地沟油, "gutter oil", a long-running food-safety scandal in China.