Commissioning and Acceptance Testing - Design-Build for Water and Wastewater Projects - page 288

A discussion of acceptance testing criteria is summarized in chapter 13; however, the
main objectives of acceptance testing to prove water quality performance of the facility are
outlined in the following list:
1. To prove that the treated water of a WWTP meets the agreed-on water qual-
ity concentrations so that the water is deemed suitable for its intended use (e.g.,
surface discharge, groundwater recharge, reuse), or finished water from a WTP
meets the agreed-on water quality concentrations so the water is deemed to be
suitable for human consumption.
2. To demonstrate plant operation over a defined period of time to show that the
process is working properly. The chemistry of treatment should be well under-
stood when developing the testing duration. For example, a biological process,
such as in wastewater treatment or in some filtration processes of water treat-
ment, may require several weeks to stabilize. Other chemistry, such as arsenic
removal by coagulation, is instantaneous and could be evaluated over a short
time period (e.g., less than seven days).
3. To demonstrate that WTP processes, which are affected by changes in the water-
shed due to seasons, work effectively during those seasons. Sometimes owners
desire testing periods to cover all seasons or the seasons when water is the easiest
or hardest to treat. The intent is to prove that the process functions as designed
when challenged by seasonal influences. This approach poses some risk to the
design-builder, because it extends the acceptance testing period, the facility is
normally operated by the owner during the time between testing periods, and the
way the plant was operated between tests may affect performance during the chal-
lenging water quality testing period. In addition, there is no guarantee that the
challenging water quality will occur during the scheduled seasonal testing period.
To meet these objectives, several key planning items must be considered, and it is
recommended that they be developed with the acceptance criteria or performance guar-
antees. Sample frequency depends on how variable the water quality is expected to be
and what level of verification is needed to prove that the plant is operating as intended.
For example, if a water source is a groundwater, the frequency of sampling the raw water
would likely be less than that for a surface water, because the concentration of contami-
nants is expected to be fairly constant. For water that contains contaminants that are
known to impact human health, the sampling frequency would likely be higher to prove
that the process is functioning well and that the contaminant is being removed.
It is important to recognize that the list of parameters to sample during acceptance
testing should include not only the parameters of interest but also any parameters that
might affect the performance of the process equipment. During the acceptance test, the raw
water or feedwater quality should be analyzed to verify that the water quality is within the
water quality envelope that is part of the performance guarantee language of the contract.
The location for sample collection needs to be clearly defined. This eliminates any
confusion when samples are collected in the field. Sample locations are often identified on
a P&ID but should also be in the acceptance test plan.