Simultaneous removal of iron, manganese and ammonia from groundwater: upgrading of waterworks in northeast China

Abstract

The municipal water supply of Songbei District in Harbin, Northeast China, relied on local groundwater which contained high concentration of iron (about 15 mg/L), manganese (about 1.5 mg/L) and ammonium (about 1.1 mg/L). The waterworks had a two-stage filtration process, including the first purification filters for the removal of iron and the second one for the removal of manganese and ammonium. The total treatment capacity was 10,000 m(3)/d. In order to double it to meet the increasing water-supply demand, the upgrading of the waterworks from operation in series to operation in parallel by the simultaneous removal of iron, manganese and ammonium in single biofilter was recommend. After inoculation of bacterial solution, aeration was enhanced from about 4.5 mg/L to almost 10 mg/L, by adding of cascaded aeration and perforated pipe spargers, to meet the oxygen demand in the biofilter. And the filter-layer was optimized, by adopting the dual-media filter, to reduce the effect of ferrous on biofilter for manganese removal. Finally, the waterworks was successfully transferred into the one-stage filtration process and the concentration of iron, manganese and ammonium in the treated water was about 0.20, 0.05 and 0.17 mg/L, superior to the national standards for drinking water (GB5749-2006). Adequate dissolved oxygen and dual-media filter are beneficial to biological manganese removal from groundwater, in the condition of high concentration of ammonia nitrogen and ferrous ion.