LOW UVT WASTEWATER IS STILL NO MATCH FOR THE TROJAN UV3000PLUS

SUPERIOR, WI

The Environmental Services Division of Public Works (ESDPW) for Superior WI is comprised of ten (10 Sanitary Sewer Districts and carries four discharge permits. The main WWTF treats an average of 3-4 million gallons per day with peak flows hitting 11 million gallons per day during storm events. Several years ago, the City was faced with a decision to rehabilitate the existing Chlorine disinfection facility or convert to another form of disinfection. After evaluating all of the alternatives, Superior chose UV disinfection over chemical disinfection for several reasons:

  • Location of the WWTF was close to several high population density areas

  • The City could eliminate the need for additional Risk Assessment Reports and Emergency Action Plans typically associated with feed chlorine gas

  • The City was required to dechlorinate with sulfur dioxide and the existing S02 system was also at the end of it’s useful life

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The City evaluated several different types of UV systems and manufacturers and ultimately chose the Trojan3000PLUS with the Automatic Chemical and Mechanical Cleaning System. The WWTF has at times a ( generally about 50 and at high flows down to 30’s) relatively low Ultra-Violet Transmittance (UVT) combined with using Ferric Chloride as a Coagulant for Phosphorus Removal. For these reasons, the chemical and mechanical cleaning system is vital to the performance of the UV System. According to Mark Simmonds the Operations and Maintenance Supervisor, “when having a UVT of less than 40%, we are typically seeing non-detect or single digit E-Coli counts in our sample. We are very happy with our switch to UV Disinfection.” The Operations staff removes the modules twice per year to recharge the chemical cleaning solution since they have a year-round disinfection permit.