Minneapolis, Kan., is just 15 minutes north of Salina near the middle of the state. The city’s drinking water is supplied through groundwater sources with high levels of naturally occurring iron and manganese. Over the years, the city had received many red water complaints from the residents, who also complained to their regional Kansas Department of Health and Environment (KDHE) office.
Layne Christensen Co. had a 50-year history of drilling water wells for the city, and, when the city administrator learned that Layne also treated water , a pilot study was contracted to determine the treatment capabilities of the LayneOx media.
The city contracted with a consulting engineer who evaluated Layne’s high-rate iron and manganese removal system against other technologies. The engineer offered the most cost-efficient option for the city over a 20-year life cycle comparison. A design for a 1,050-gal-per-minute (gpm) system emerged with all of the wells piped to the treatment plant location on the East side of town.
Efficient Approach
The city has three wells with iron levels ranging from 1.3 mg/L to 2.0 mg/L. The manganese ranges from 0.9 mg/L to 2.0 mg/L. Based on pilot study results, KDHE approved a LayneOx design for a loading rate of 9.2 gpm/sq ft. This was the highest rate ever granted by the state for a water treatment system.
The plant also uses a backwash recovery system designed by Layne, which recovers most of the dirty backwash water. The backwash tank catches the solids removed from the filter during the cleaning cycle, letting them settle and then returning clear supernate from above the solids back into the influent of the treatment system. This approach results in a plant efficiency rate of 99%.
The plant was complete in February 2007. To date the effluent iron has averaged 0.053 mg/L and the manganese has averaged 0.018 mg/L, which are both considerably below the U.S. Environmental Protection Agency Secondary required levels of 0.30 mg/L for iron and 0.050 mg/L for manganese. Minneapolis received the Kansas Plant of the Year Award in 2007 for its size classification.
