Disinfection of Ultra-Low UVT (<1%) Industrial Wastewater
Great results in difficult liquids
A large food processing plant in New Zealand is the largest wastewater producer that discharges into the local council trade waste scheme. The Council was implementing a new trade waste consent which required all industries to reduce their enterococci concentration.
The processing plant already carries out some onsite treatment of their wastewater before discharging into the trade waste scheme. This consists of milli-screening, polymer and lime dosing, and clarification.
The solids removed during the wastewater process are separated for composting and therefore the plant owners were opposed to using chemicals such as metal coagulants (alum, ferric, etc.) in their wastewater system which would prevent the solids from being biodegradable. Chlorine and ozone disinfection were also deemed unsuitable due to the high organic content of the wastewater.
Ultraviolet disinfection was considered as a possible solution. However, due to the UVT of their wastewater typically being less than 1% and their total suspended solids being up to 400 mg TSS/L, conventional ultraviolet submerged lamp systems were considered unviable. NovoLabs™ Supercritical UV™ disinfection system was recommended to the processing plant by a third-party supplier and so an onsite trial using NovoLabs™ mobile test unit was commissioned in order to assess its disinfection capability on the plant’s ultra-low UVT effluent.
The Supercritical UV™ disinfection system achieved an average of 99.996% (or 5.0 log) removal of enterococci from effluent which had a UVT of less than 1%!
Figure 1: Enterococci removal after passing through the Supercritical UV™ disinfection system. UVT is less than 1%
Supercritical UV™ disinfection system purchased based on results
Based on these results, the project engineer at the processing plant concluded that “The unit has shown satisfactory levels of disinfection for enterococci in most cases, even with UVT in the order of 0.1%”. As a result of the testing, they purchased a full-scale Supercritical UV™ disinfection system unit from NovoLabs™ for their processing plant.
