INVESTIGATION OF SOIL TREATMENT SYSTEMS FOR SEPTIC TANK EFFLUENT. II. SOIL pH, TOTAL CARBON AND NITROGEN
Eight sand filter systems and eight infiltration systems were investigated for soil pH, total carbon and nitrogen. All of the systems have been in use for several years. The soil from the systems was analyzed by standard methods. The soil pH of the sand filter systems clearly reflected the pH of the wastewater. As expected, the amounts of total C in the systems were highest near the distribution pipe and decreased downwards. Also the highest amount of total N, organic N and ammonium N were found near the distribution pipe. Nitrate N is negatively correlated with ammonium N due to improving oxidizing conditions with depth. Differences along the pipe in the systems and between the locations can at least partly be explained by differences in the design of the systems, including the design of the perforated distribution pipe, the slope of the pipe and the loading of the system. It can be concluded that for some of the systems the reduction in N has been relatively good.