Dewatering for Iron and Manganese Removal

Richard Cavagnaro Jr.

In October 2010, AdEdge Water Technologies LLC was contacted by JVA Inc. to provide an iron and manganese dewatering system for residences in Boulder, Colo.

Raw groundwater contained iron levels between 4.6 and 7.4 mg/L and a manganese level of 4.5 mg/L, well above the U.S. Environmental Protection Agency (EPA) secondary maximum contaminant levels (MCL) of 0.3 mg/L and 0.05 mg/L respectively. Iron and manganese levels need to comply with the EPA MCLs in order to discharge into the sanitary sewer and meet applicable discharge criteria.

Implementing the Treatment System

The treatment system chosen features a skid-mounted AD26 oxidation and filtration unit sized for a maximum design flow of 50 gal per minute. The model APU26-3060CS-4-AVH utilizes AdEdge AD26 media in a four-vessel carbon steel configuration in series.

Each 30-in. diameter treatment vessel contains 13.5 cu ft of manganese dioxide oxidation/filtration media. The product is a NSF 61-certified black filter media used for the removal of arsenic, iron and manganese. The system is equipped with automated control valves and a harness, a central control panel with programmable logic controller (PLC) and a color user interface screen.

System features also include differential pressure switches, a control panel and local gauges, flow sensors and totalizers, and a central hydraulic panel with sample ports for a complete functioning packaged unit. An autodialer was integrated in the treatment system for ease of operation. Prior to the treatment system, two supply pumps were provided by AdEdge.

Measuring Results

An AdEdge AD-IN Chemical Feed module using liquid sodium hypochlorite via an in-line injection was introduced ahead of the filtration system with a chlorine feed and monitoring system to enhance the removal process. The PLC initiates backwashing of the treatment system twice daily, depending on the incoming levels of manganese to remove any suspended solids that may accumulate in the bed. 

In addition to the backwash supply system, the company also provided an H2Zero recycle backwash system that reclaims 100% of the settled backwash water. The settled iron, manganese and suspended solids form a low-percent-solids sludge that can be dewatered and disposed of in a solid waste landfill. After the water is treated by one system, the water is then treated again by a second treatment system.

The model GAC-4260CS-2-MVH utilizes AdEdge GAC (granular activated carbon) in a two-vessel carbon steel configuration in series. Each 42-in. carbon steel vessel contains 30 cu ft of GAC for polishing the water prior to discharge to the sanitary sewer.

The system commenced operations in March 2011. Since then, iron and manganese levels measure below EPA secondary MCLs.

Richard Cavagnaro Jr. can be reached at [email protected] or 678.835.0052.