Sanitary Sewer and Wastewater Treatment Plant Improvements

Pocahontas, IA | Water


ISG developed cost-savings solutions to lower the chloride and e. coli effluent levels to meet State standards for the City of Pocahontas’s (City) wastewater treatment plant and recommended efficiency improvements to its aging sanitary sewer system.


Major components of the City’s wastewater treatment facility were not functioning properly, and in some cases failing. Improvements needed to be made to the entire wastewater system to stay in compliance with State chloride and e. coli effluent limits.


ISG approached this multi-faceted project in two phases addressing both wastewater treatment plant improvements and sanitary sewer infrastructure upgrades. In phase one, ISG developed a comprehensive facility plan, which began with an evaluation of the wastewater treatment plant. The assessment revealed the plant was running at an average flow of 1 million gallons per day (GDP). A nutrient reduction strategy would be required if the flow rate continued and would cost the City millions of dollars in major infrastructure improvements. To avoid this costly upgrade, ISG conducted an evaluation of the sanitary collection system and developed a plan to rehabilitate the system. Simplified solutions reduced inflow and infiltration (I/I) flows by 15%, minimizing the risk of reaching 1 million GPD. Additional system updates included the replacement of deteriorating manholes and sewer main lining.

Phase two directly addressed compliance of chloride and e. coli effluent limits per State requirements. ISG is conducting a wastewater treatment plant study to determine the most effective way to manage unsafe chloride levels in the water. The City was granted a two-year extension to provide adequate time for the study and to make necessary changes to lower chloride levels.

The process of reducing e. coli effluents involved a review of the entire plant. A range of improvements were implemented including, headworks equipment, process piping, grinder and grit system rehabilitation, ultraviolet (UV) disinfection system, aeration system upgrades, and return and waste activated sludge system. Control system upgrades were also included, along with the installation of a standby generator, and variable frequency drive replacements. The water resource team is currently testing a pilot for new wastewater treatment technology. Once the pilot test results are evaluated, ISG will begin designing a new City water plant.

To extend the life of the entire plant and protect the City’s wastewater investments, ISG is also replacing the facility’s heating, ventilation, and air conditioning (HVAC) system. The new HVAC system will improve air quality thereby reducing the deterioration rate of critical treatment facility components.

The City of Pocahontas is experiencing significant return on investment from improvements made to the sanitary sewer system and wastewater treatment facility. The new components have improved system operability and made the facility more energy efficient. Wastewater operators are able to maintain the plant with ease, and the system meets e. coli effluent limits with no issues. Together, the treatments have resulted in significant cost-savings solutions to the City.

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