you can testing all Heavy Metals and Pesticides Residues, PAHs, PCBs, Using GC or HPLC and i Can helping you for Extraction and Protocol for all analysis , Good Luck and have a good day,
This might depend on there the wastewater is going - irrigation, river or the sea.
I use the Microtox test a lot. It is a very easy to use (commercially available) kit based on a fluorescent marine bacteria. It is very sensitive to many toxic chemicals.
If you use the water for irrigation the duckweed (Lemna sp.) test would be my next choice. It is very easy to perform without special skills or advanced laboratory.