Monday, November 13, 2006

Removal of the Nitrogen, Phosphorus, and Fecal coliform in Dairy Effluent using Multi-Soil-Layer (MSL) systems.

Rosalin Pattnaik, Univ of Hawaii at Manoa, Dept. of Tropical Plants and Soil Sciences,, 3190 Maile Way St. John 102, Honolulu, HI 96822, Russell Yost, Univ of Hawaii at Manoa, Dept. of Tropical Plants and Soil Sciences, 3190 Maile Way St. John 102, Honolulu, HI 96822, and Guy Porter, Univ of Hawaii at Manoa, University of Hawaii-Manoa, 3190 Maile Way St. John 102, Honolulu, HI 96822.

The disposal of dairy effluent in Hawaii is a current concern because of possible contamination of ground water and coastal water. The objective of this study was to quantify the effectiveness of MSL systems in removing nitrogen (N), phosphorus (P), and fecal indicator organisms (Fecal coliform) from the dairy effluent and to explore ways to increase MSL efficiency. Four MSL units were constructed in two treatments with two replications. The two materials for the aerobic layer were commercial Perlite and Leilehua soil (Oxisol). The anaerobic layer was based on the Honouliuli soil (Vertisol). Untreated dairy effluent was applied to the MSL systems during a 12 month period at a rate varying from 272 to 545 L m-2 d-1. The percentage removal of total N (TN) for the first 10 months in both systems averaged to 47% (13-96%) whereas during the last two months, it decreased to 9% and 21% for two-soil and soil-perlite system, respectively. This drop may due to a pause in the effluent delivery or an inefficient denitrification process. The percentage removal of dissolved reactive P (DRP) was greatest in the system with Oxisol in the aerobic zone, an average of 81% (42-98%) in contrast to the soil-perlite system, 39% (3-97%). High P adsorption capacity of the Leilehua soil probably caused greater removal of P in the two-soil system than in the soil-perlite system. The soil-perlite MSL was more effective in reducing fecal coliform bacteria (63%) versus the two-soil system (58%), which may due to the tropical soil, which are known to contain large amount of coliform bacteria. The results indicate that MSL units can be effective in removing N, P, and fecal coliform from dairy effluent with low cost materials while occupying a small amount of space.

Handout (.pdf format, 194.0 kb)