The treatment process at the City of Woodland's Water Pollution Control Facility (WPCF) is being enhanced to improve nitrogen removal. The existing oxidation ditches will be converted to a once through treatment process. Computational fluid dynamics (CFD) modeling was used to evaluate mixing of solids with the converted tank, using a solids transport equation within the computation. The type, location, and orientation of mixers in anoxic regions were evaluated to ensure solids remained in suspension and well mixed. The aerated zone mixing was evaluated with a multi-phase model to verify the injected air would mix the complete trapezoidal cross section, including through a 180-degree bend.

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Facing stringent wastewater discharge limits for trihalomethanes (THMs), the City of Turlock has investigated treatment alternatives for reducing THM concentrations of discharges from the City of Turlock Water Quality Control Facility (WQCF). The WQCF currently uses chlorine disinfection and THMs are byproducts of chlorine disinfection processes. THMs are regulated because they are classified as a human health risk for drinking water services. WWTPs in California facing similar limits typically replace their chlorine disinfection process with UV disinfection; however, UV disinfection facilities have significantly higher capital and operating costs.An alternative to replacing the existing chlorine disinfection system is to remove the THMs from the chlorinated effluent. Packed tower air stripping may be a technically viable option for doing so. The City tested a pilot packed tower air stripper at the WQCF and initial results indicate packed tower air stripping may be an economical alternative to meeting their upcoming THM limits.