Technical Report No. 1
Reginald H. F. Young, L. Stephen Lau, Nathan C. Burbank
A laboratory study was undertaken to determine the ability of four Oahu soils, Lolekaa, Lahaina, Manana, and Wahiawa, to remove ammonia, ABS, and coliforms from water percolating continuously through saturated soils. The soils utilized were chosen on the basis of their wide occurrence on the island in areas where percolating water may enter directly and in quantity into the ground water body that principally provides the island’s domestic water supply. All four soils had a high clay content and low pH. Laboratory tests were conducted with 10-ml burettes and subject to continuous saturated flow. Each contaminant was applied in solution one at a time to a fresh soil sample. Tap water was used for ABS and ammonia nitrogen while sewage was used to study coliform removal. All soils were effective in the removal of ammonia and ABS. One-hundred percent breakthrough for ammonia occurred after a throughput volume of 345 to 470 times the gross soil sample volume. For ABS it was 15 to 53 times the gross soil sample volume. The total exchange capacity for ammonia ranged from 29.3 to 50.1 micrograms of ammonia per gram of soil. The total adsorptive capacity for ABS ranged from 8.6 to 36.4 micro-grams of ABS per gram of soil. The applied concentration of ammonia was approximately 7.1 mg/l as found in a primary clarifier effluent and that of ABS was approximately 5.5 mg/l as found in a final clasrifier effluent. The results of coliform removal from percolating liquids were not conclusive because of small soil samples and the loading procedures. Preliminary tests verified some of the general principles developed elsewhere for effective coliform removal by ground disposal of sewage. The final clarifier effluent from a trickling filter was passed continuously through a 30″ column of Wahiawa soil and an initial coliform reduction of about 90% was effected.