I am currently a ZDHC Accepted Wastewater Laboratory for the ZDHC Wastewater Guidelines V1.1, do I need to apply again for the ZDHC Wastewater Guideline V2.1?
Yes, all current ZDHC Accepted Wastewater Laboratories also need to follow the application process to become accepted for ZDHC Wastewater Guidelines V2.1 as well. All Wastewater Laboratories can start their application process for ZDHC Wastewater Guidelines V2.1 acceptance from 1 April 2022 onwards. More information on this process can be found here: ZDHC Approved Wastewater Laboratory - Application Criteria
How should you proceed with sampling when there is more than 1 discharge point at a facility?
If there is more than one discharge point at a facility, a sample from each discharge point should be collected and tested separately as per the applicable type of discharge (direct, indirect)
In the case of indirect discharge, if homogenization tanks are present, how should the sample be taken?
Point 1: In an HT (homogenized tank) the retention time needs to be 12 hours (calculated and confirmed by the laboratory sampler as per the formula given below).
Retention time (hours) = total volume of the tank (m3) flow rate of effluent (m3/hour).
Indirect discharge with pretreatment:
The laboratory collects untreated wastewater (point 1: single grab in the HT) and also collects effluent (point 2: single grab if HT is present or point 3: 6 hours sample if no HT is present).
Indirect discharge without pretreatment:
The laboratory collects only untreated wastewater (that is also effluent) as a single grab from HT (point 1) to test MRSL & 5 metals.
Is a grit removal screen considered a pretreatment when conducting wastewater testing?
Grit removal systems are generally classified into three categories A:
Note: Coarse screens 60-150mm is not considered pre-treatment.
Where there are multiple factories discharging into a central ETP, owned by 1 facility, is this considered direct or indirect discharge?
In a situation where multiple factories are discharging to a central ETP owned by one facility, the following sampling and testing are acceptable:
Sample and test the raw untreated wastewater from each factory. Consider them as “indirect discharge without pretreatment” facilities.
Sample and test the ETP-treated discharge (effluent). Consider them “direct discharge”, and all the factories can report that data. Individual factories do not have to collect and test the ETP effluent, they can share that data.
Where a facility is storing its wastewater in containers, then sending it externally for treatment how should sampling be done?
There could be two scenarios here.
Scenario 1: “direct discharge” if the third-party facility only treats the wastewater of this particular factory without mixing them with any others. Maybe due to the lack of space to build an ETP, the factory may have it externally. All MRSL parameters, conventional parameters and anions, heavy metals, and of course, sludge parameters should be tested according to Table 4A-D based on the disposal pathway.
Scenario 2: "Indirect discharge without pretreatment”. If the facility stores the wastewater and then sends it to an external treatment plant, the sampling point should be from the container and the parameters applicable to indirect discharge without pretreatment (i.e the MRSL and 5 metals) should be checked. If any pretreatment of the wastewater is carried out before storing it in a container and sending it to the external treatment party, then the effluent sample, taken from the container after the pretreatment process, should be sampled to test 5 heavy metal parameters while MRSL parameters should be tested in the untreated wastewater (before pre-treatment). Any sludge that is generated due to this pretreatment process (such as fine/micro screening) should be collected and tested according to Tables 4A-D based on the disposal pathway.
How is residue from screening, that is not disposed of as sludge but reused within the production process, considered?
At an indirect discharger, if the residue is not disposed/incinerated, but goes back into the production process on-site, it is not considered to be pre-treated. Therefore is not required to be tested as sludge.
If there is no flow meter on the wastewater discharge and it is not possible to perform a calculation of the flow rate discharged because the pipe/tub is underground, what should be done?
Then the laboratory needs to estimate the flow rate based on the below formula and mention that in the EDR. Data for the calculation could be obtained by the facility itself.
The flow rate in m3/hr = Total volume of effluent treated (m3/day)/ Total hours of ETP operation (hr/day).
How does a wastewater laboratory verify confirmation of the boron, and zinc salt for the ZDHC Wastewater Guidelines V2.1?
The borate, zinc salt limit value is applicable to textiles only, the limit is 100 μg/L.
This is based on results for total boron and total zinc individually as determined by the ICP test. This means that total boron and total zinc values should be less than 100 μg/L to be conformant to the ZDHC Wastewater Guidelines V2.1.
Where total boron is > 100 μg/L and total zinc are < 100 μg/L (or vice versa) the sample is still conformant to the ZDHC Wastewater Guidelines V2.1.
Laboratories should input the values for total boron and total zinc in the EDR template when uploading the test results.
What should be done if the sampler is not able to measure the temperature difference parameter of the upstream receiving body?
The temperature difference parameter in ZDHC Wastewater Guidelines V2.1 is only applicable to those facilities that are directly discharging the treated effluent to an upstream receiving water body. Where effluent is discharged directly to the ground, in a municipal sewer or another environment, the temperature is not to be evaluated. The sampler must confirm that the discharge is made to an upstream water body during the site visit to sample the wastewater.
Where the receiving body is inaccessible, the sampler's own safety is at risk in accessing it or the upstream receiving body is located far away from the facility (e.g. a pipeline from the facility that goes several kilometres into the sea), then the sampler should not carry out this on-site test and the temperature parameter will be not applicable.
In both the above cases, since the temperature parameter is not measured, it will appear as a white row (not applicable) in the ClearStream report and the maximum score for conventional parameters will be lowered by 3 points in the ClearStream report.
What should a sampler do if they are not able to visually monitor the persistent foam of the upstream receiving body?
In case the receiving body is inaccessible or the sampler's own safety is at risk in accessing it, the upstream receiving body is located far away from the facility (e.g. a pipeline from the facility that goes several kilometres into the sea), then the sampler should not carry out this on-site test and the parameter will be not applicable.
How should a negative temperature difference (the temperature of the receiving body is lower than the temperature of the discharged effluent) be reported?
A negative delta result for temperature difference indicates that the discharged effluent temperature does not cause any increase in the temperature of the receiving body. This should be reported as a negative value by the testing laboratory and it will be treated as “Aspirational level” and scored accordingly in the ClearStream Report.
What should Wastewater Laboratories test under the requirements for PFCs (Table 1 O) to verify conformance to the ZDHC Wastewater Guidelines V2.1?
Wastewater laboratories can refer to the list of ‘marker chemicals’ given in the ZDHC MRSL V3.1 document and test these marker chemicals in the wastewater sample to identify the related substances of PFOS and PFOA. Wastewater Laboratories can also refer to the PFAS Guidance Sheet document given in the e-MRSL V3.1 to gather the list of PFAS and CAS numbers.
What is the correct approach to Wastewater manual sampling?
As per ZDHC SAP V2.1, ZDHC Approved Wastewater Laboratory sampling personnel can collect separate samples by hand for no less than 6 hours, with no more than 1 hour between separate samples. That means the sampler should collect no less than 7 samples and each separate sample shall be of equal volume and combined to produce 1 composite sample. The composite sample container must be cooled at 4 degrees Celsius during sampling.
What does it mean by “analysed like a wastewater sample, and reported as a sludge sample” for liquid sludge as per SAP guidelines?
This means that the analysis/testing procedure should be similar to Wastewater testing since this is "liquid" sludge, not solid sludge. But the laboratory needs to report this as sludge using parameters applicable to sludge only on a weight/volume basis (mg/L).
What is the process of completing composite sampling of wastewater, based on SAP Guideline V2.1 ?
The minimum amount of samples is 7 and the lab can collect them within a time period of 6 hours (or a length of time that represents the entire production process cycle which could be less than 6 hours). Ensuring no longer gap than 1 hour between 2 samples.
What will happen to boron flame retardants in Table 1J if the total elemental boron value is more than 100μg/L?
If the total elemental boron is more than 100 μg/L, then all boron flame retardants in Table 1J (Boric acid, Diboron trioxide, Disodium octaborate, Disodium tetraborate anhydrous and Tetraboron disodium heptaoxide, hydrate) contain the same value obtained for the total elemental boron and will be over the threshold limit. The same theory is applicable to less than 100 μg/L values as well.
What are the sampling points to collect samples for MRSL and heavy metals testing of a facility with “indirect discharge without pre-treatment"?
Samples to test both MRSL parameters and five heavy metals should be collected from the raw (untreated) effluent which directly comes from the facility before discharging into the Central Effluent Treatment Plant (CETP).