The removal of pollutants present in domestic wastewater by an inorganic medium.

Abstract

The removal of polluting parameters present in domestic wastewater, by the Biolat septic tank was investigated. Results obtained indicate that the Biolat media was responsible for the removal of ammonium and phosphate. Biological and physical processes, within the septic tank itself, were responsible for the removal of nitrate, BOD, COD, suspended solids and E.coli. The adsorption capacity of Biolat for both ammonium and phosphate was determined using Biolat columns and pure solutions of ammonium and phosphate. Investigations revealed that the mechanism of phosphate removal was by physical adsorption into the Biolat matrix. The removal of ammonium was by means of cation exchange. Both adsorption phenomena obeyed the Freundlich adsorption isotherm. Contact time between the Biolat and ammonium or phosphate was important. A retention time of greater than one day was required when influent concentrations exceeded 1000 mg/1 of phosphate or ammonium. Desorption of adsorbed phosphate occurred when water was passed through the saturated Biolat. The desorption process was gradual and necessitated the passage of large quantities of water through the Biolat columns. The desorption of phosphate from Biolat was very efficient because it was merely held in the Biolat matrix by physi-sorption. Some adsorbed ammonium was also desorbed using distilled water. However, the desorption efficiency of ammonium was much lower than for phosphate. The reason for this was due to ammonium being more strongly bound in the Biolat matrix. The effect of pH and grain size on adsorption were also investigated. The grain size of Biolat was important in adsorption only in the initial stages of contact between Biolat and phosphate or ammonium. The adsorption of phosphate and ammonium by Biolat was relatively unaffected by the the pH of the solution.