Disinfection of ultra-low UVT (<1%) industrial wastewater

Great results in difficult liquids

Cedenco Limited has a large food processing plant in Gisborne. This facility is the largest wastewater producer that discharges into the Gisborne council trade waste scheme. The Gisborne council are implementing a new trade waste consent which requires all industries to reduce their enterococci concentration.

Cedenco already carry 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 Cedenco are opposed to using chemicals such as metal coagulants (alum, ferric, etc) in their wastewater system that would prevent the solids from being biodegradable. Chlorine and ozone treatment were also deemed unsuitable due to the high organic content of the wastewater.

UV disinfection was considered by Cedenco as a possible solution. However, due to the UVT of their wastewater typically being less than 1%, conventional submerged lamp UV systems were considered unviable. NovoLabs™ Supercritical UV™ (SCUV) technology was recommended to Cedenco 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 Cedenco’s ultra-low UVT effluent.

As shown in Figure 1, SCUV achieved an average of 99.996% (or 5.0 log) removal of enterococci from Cedenco’s effluent which had a UVT of less than 1%!

Figure 1: Enterococci removal after passing through the SCUV device. UVT is less than 1%

SCUV unit purchased based on results

Based on these results, the project engineer at Cedenco declared that “The SCUV unit has shown satisfactory levels of disinfection for Enterococci in most cases, even with UVT in the order of 0.1%”. Based on the results of this testing Cedenco purchased a full-scale Supercritical UV™ unit from NovoLabs™ for their Gisborne processing plant.

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Novolabs™ Supercritical UV™ Disinfection — UV Treatment for Low Clarity Liquids