Use of Biological Filters for Treating Agricultural Drainage Effluents1
- K. R. Reddy,
- K. L. Campbell,
- D. A. Graetz and
- K. M. Portier
A field study was conducted for 1 year (1979–1980) to evaluate the efficiency of reservoir systems stocked with aquatic macrophytes for reducing nutrient levels of agricultural drainage water. Reservoir R2 containing water hyacinths (Eichhornia crassipes (Mart) Solms), R3 with elodea (Egeria densa Planch), and R4 with cattails (Typha latifolia L.) were connected in series by riser panels. Drainage water was pumped through the plant stands in the order of water hyacinths, elodea, and cattails. Drainage water was also pumped into a reservoir (R5) containing submerged Chara spp. Nutrient removal rates by each treatment system were calculated using water flow data.
Nitrate and ammonium removal rates by the treatment systems were in the range of 1–14 kg N/ha per day and 0.1–2 kg P/ha per day, respectively, while soluble P removal were in the range of 0.05–1.3 kg/ha per day. Reservoirs with aquatic macrophytes were found to be more effective than the reservoir containing Chara spp. About 78–81% of the input NO3− and NH4+, and 54% of the input soluble P were removed in 3.6 d by the R2 reservoir containing water hyacinths. Allowing the water to flow through an additional reservoir, R3, and increasing the residence time by an additional 3.6 d increased NO3− removal efficiency to 91% and soluble P removal efficiency to 71%, but NH4+ removal efficiency was not affected. Allowing the water to flow through the third reservoir (R4) and increasing the residence time by an additional 2.2 d, improved soluble P removal efficiency by an additional 14%.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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