Soil and minespoil fill as media for renovation of nitrogen and phosphorus in domestic wastewater

Abstract

Development of Appalachian coal mining regions of the USA has been severely hampered by lack of domestic waste disposal technologies suited to fills. The suitability of on-site wastewater treatment and disposal systems (OSWTDS) in fill material is uncertain due to the effects of surface mining on soil physical properties. This research was conducted to evaluate the potential for renovation of N and P present in domestic wastewater by fills produced from mining operations. Nitrogen and P were chosen because of their potential adverse environmental impacts. Soil-fill (a mixture of Jefferson, fine-loamy, siliceous, mesic Typic Hapludult and Muskingom, fine-loamy, mixed, mesic Typic Dystrochrept soils) and minespoil (spoil)-fill (blasted rock material associated with the Taggart Marker and Low Splint Bench coal seams of the Upper Middle Wise Formation) were used in this study. Septic tank effluent (STE) and sand filter effluent (SFE) were applied to spoil-fill columns at four loading rates (0, 5.4, 10.8, and 21.6 L m-2d-1) and spoil-fill columns at one loading rate (21.6 L m-2d-1) for a period of 20 wk. Renovation of wastewater was assessed by determining the concentration of N and P present in column leachate. Reduction of inorganic N (NO3- + NH4+), based on N/Cl ratios, ranged from 14.9 to 32.1% after the varying application rates of STE and SFE passed through the soil columns. However, leachate NO3--N concentrations were still above the 10 mg-1 drinking water standard. The quantity of P emerging from the spoil-fill columns (3.0 mg P L-1) was higher than anticipated and may be related to the indigenous P present in the minespoil. Sorption of P in the soil-fill column decreased with increased STE and SFE application (reductions ranged from 99.1 to 74.4%). Results from this study indicate that there is potential for renovating wastewater in OSWTDS in selected soil-fill areas in reclaimed minelands.