Report Number: 18
Year: 1980

Laboratory Application of Secondary Sewage Effluent to Argillaceous Limestone

Secondary sewage effluent and river water (control) were applied to a series of laboratory lysimeter containing argillaceous limestone. Nitrates naturally deposited in the limestone were leached after semi-continuous water loading. Mass balance data of river water percolate with low nutrient input levels showed nitrogen removal and phosphorous release. Phosphorous release was attributed to fine particulate matter flushed from the lysimeters. River water leachate was generally high quality. Sewage effluents with high nitrate concentrations leached through the limestone media yielding mean percolate concentrations of 8.0±0.4 and 14.3±8.7 mg/L at a depth of 2.74 m. The limestone was unable to remove nitrogen. Phosphorous was initially stripped from the sewage effluent with 76 to 90% removal after percolating through 2.74 m of limestone media. Phosphorous breakthrough occurred in the top 0.91 m of limestone after 70 L of water loading. The estimated phosphorous adsorption capacity was low at 0.011 kg-P per m3. Coliform bacteria removal efficiencies in the sewage runs were >95% at the 0.91-m depth and >99% at the 1.83-m depth. In relation to the limestone's inability to remove nitrogen and phosphorous, the limestone infiltration/percolation system was concluded to be a disposal option and not a treatment alternative.

Peter A. Cowan
Russell N. Clayshulte