This project included extensive rehabilitation and expansion of an existing water treatment plant for the City of Oakland, Iowa, which operates a combination of shallow alluvial and deep wells. The city’s largest customer, a food production facility, consumes the majority of water produced and requires precise water quality control. All water was previously treated by the lime softening process. Water chemistry in the deep wells wasn’t conducive to treatment by the existing lime softening process. In addition to treatment limitations, finished water demand often exceeded rated plant capacity.
Plant upgrades included renovation of selected existing plant components and the construction of a new reverse osmosis (RO) treatment process to effectively treat the deep well water. Shallow well water is treated by the existing lime softening process.
The new treatment system included piping modifications to separate source water as selected by the plant operators. The new plant included pressure filters and sodium permanganate chemical feed for the removal of iron and manganese. Water is then treated with sodium bisulfite to protect downstream treatment equipment from the effects of strong oxidizers added upstream. The new treatment process includes the use of an RO treatment system to provide effective softening and precise finished water quality control.
Water is treated independently by the two processes, utilizing the benefits of each. The RO process provides effective hardness reduction for deep well water but can create water chemistry, pH, and stability concerns. Water treated by the lime softening process is naturally much higher in pH and is blended with the RO effluent to economically boost pH and improve water stability while minimizing additional chemical costs.
Water is blended in a new 600,000 gallon reinforced concrete ground storage reservoir. This 70-foot diameter reservoir provides disinfection contact time and reserve storage capacity. High service pumps then draw water from the new reservoir to be sent to the distribution system.