違法接駁污水渠

Hope you don't mind I answer your question in English. I can type 1,000 times faster in English than Chinese.

環保署 has nothing to do with 違法接駁污水渠, unless the 污水渠 is connected to a river, ocean, or other public area.
Usually it is the Building Deparpment's job to make sure all sanitary sewer connections are properly installed.

Most cities in the world have some kind of Plumbing Code to follow. Most Plumbing Code talks about the size (diameter) and material of sewer pipe that needs to be installed, depending on the size of the building and number of plumbing fixtures (toilet, sink, shower, etc) Typical size are 4 inches to 12 inches, typicall material are cast iron, ABS.

Most sanitary sewer goes from the building to a sewage treatment plant, where the sewer (dirty water) is treated (cleaning the dirty water) before it is released to river or ocean. However, some super dirty water, e.g. toxic, posion, grease and other pollutents are required to go thru some onsite treatment before they can enter the regular sewer line. Owner of a new factory producing toxic waste maybe required to put in his private treatment / filtration system. The review and inspection of said facility is handled by both the building department and 環保署.

咩係違法接駁污水渠 : if you don't follow the Codes when connecting the sewer system, you have broken the law.
For example, you installed a plastic pipe when a cast iron pipe was required, you dump all the dirty water to a near by river instead of connecting to sewer treatment plant.
環保署係呢方面有咩監管 : they are involved in the initial stage of building construction, making sure all things are done according to their Rules and Regulations. But no more 監管 after everything is built, they go home !
They will not know the violations out there until someone files a complaint. Then they will start an investigation (long time), then issue orders (long time), if owner does not co-operate they go thru the court (long time) to issue citation. If found guilty, the business may be closed, owner will be fined ... or whatever the Judge decides.