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In what is believed to be the most intensively studied application of hypolimnetic aeration in awater supply reservoir, significantly lower concentrations of iron, manganese, phosphorus, sulfide,chlorine demand, and ammonia have been observed since the installation of hypolimnetic aerationsystems in two water supply reservoirs in Virginia. Substantial reductions in sulfide and iron in thelake bottom waters were observed immediately after aerator installation even though dissolvedoxygen concentrations were not maintained in the bottom waters throughout the period of thermalstratification. No reduction and even increases in total manganese concentrations were observed inthe bottom waters of the lakes in the first several years following aerator installation. This trendwas likely related to the increased mixing that occurred due to aerator operation and an increase inhypolimnetic (bottom water) temperature. Following the expansion of aerator capacity (and theamount of oxygen transferred to the lake bottom waters) dissolved oxygen concentrationsimproved in the hypolimnion and manganese concentrations were observed to decrease over aperiod of several years. Water quality improvements associated with hypolimnetic aerationallowed discontinuation of prechlorination at Norfolk's water treatment plants to remove iron andmanganese and the reduction in chlorine demand of the lake water contributed to lower totalchlorine usage. Due to elimination of prechlorination and lower chlorine doses for primarydisinfection, THM concentrations in compliance samples were also observed to decrease followingaeration. Increases in filter run times and concurrent lower filter backwash water losses were alsoobserved leading to an increase in system capacity. Includes 6 references, tables, figures.

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Edition: Vol. - No. Published: 06/01/2006 Number of Pages: 19File Size: 1 file , 1.2 MB