Abstract
Electric arc furnace (EAF) steel slag filters were investigated for their efficiency at reducing the concentration of phosphorus (P) from dairy farm wastewater in Vermont. The primary objective for this study was to examine the use of in series design on filters’ performance in P removal from dairy farm wastewater at subzero temperatures. Other research objectives were to investigate operational parameters such as the effects of total suspended solids (TSS) daily mass loading rates and of alternating feeding and resting periods on EAF steel slag filters’ TSS, dissolved reactive phosphorus (DRP) and total phosphorus (TP) removal efficiencies and filter system life-span. The utilization of in series filter design increased filter DRP removal efficiency by 35%. In series design also allows for alternating feeding and resting periods, which resulted in a 16%, 57% and 74% increase in TSS, DRP and TP removal efficiencies, respectively, by the first filter in series over a single period. Additionally, the system life span was extended 3.25 fold (from 52 to 169 day). Based on this research, we recommend alternate feeding and resting cycles and in series design to be integrated in the design of EAF steel slag filter systems for highly concentrated agricultural effluents in cold climates.
Highlights
Over the past decade the eutrophication of surface waters caused by excess phosphorus (P)pollution from agricultural operations has become one of the major water quality issues worldwide [1,2]
The filters were fed at an average total suspended solids (TSS), dissolved reactive phosphorus (DRP) and total phosphorus (TP) daily loading rates (LR) of 1.08 ± 0.004 g TSS kg−1
The results described here enhances our knowledge of Electric arc furnace (EAF) steel slag filters and further demonstrates their potential for the treatment of milk parlor effluents
Summary
Over the past decade the eutrophication of surface waters caused by excess phosphorus (P)pollution from agricultural operations has become one of the major water quality issues worldwide [1,2]. The use of confined animal feeding operations (CAFOs) results in the concentration of animals, and their associated wastes, wastewater and storm runoff into increasingly smaller plots of land and regions of the U.S This causes elevated levels of nutrients, suspended solids, oxygen demanding organisms and heavy metals in agricultural waste effluents, and poses a threat to surface and ground waters [3]. U.S EPA revised the national Concentrated Animal Feeding Operations (CAFOs) rules to define which farms are required to obtain a National Pollutant Discharge Elimination System (NPDES). Permit [7,8] The result of these revisions was the determination that all medium and large CAFOs are required to obtain a NPDES permit if they have any discharge of agricultural wastewater to any waters of the state [7]. The TMDL regulation requires all CAFOs to implement waste storage or treatment systems to prevent discharges from production areas and ensure that the farm is in compliance with state and federal regulations [8,9]
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