In a situation where multiple production units with separate business licenses are discharging to a central effluent treatment plant (CETP) owned by one facility with a separate business license, the following sampling and testing are acceptable:

Sample and test the untreated wastewater from each production unit, which the ETP does not belong. Consider these as “indirect discharge without pretreatment” facilities and test the relevant parameters based on the discharge volume of each production unit.

Consider the facility with the ETP as a “direct discharge” only if the facility is finally discharging the effluent to the environment. Sample and test its untreated wastewater for MRSL parameters based on the discharge volume and treated effluent for the conventional parameters, anions and heavy metals. 

If the facility is discharging the effluent to CETP, then this should be classified as Indirect with pre-treatment (with or without sludge). And the discharged wastewater (effluent) should be sampled and tested for 5 metals i.e. arsenic, cadmium, chromium VI, lead, mercury as well as sludge.

Sludge should be tested based on the major sludge disposal pathway.

The values for sludge, metals, conventional parameters and anions, are applicable only to the facility with the ETP,  not to the other facilities. 

Each production unit needs to have separate AIDs to report their wastewater and sludge results on ZDHC Gateway.