Biological Reduction of Nitrate from Secondary Treated Wastewater Using Sulfur-Limestone Reactor

Nebras Hamdan

Abstract: This study evaluates the efficiency of autotrophic denitrification using a sulfur-limestone biofilter in removing nitrates from synthetic wastewater. Four nitrate concentrations (10, 45, 75, and 100 mg/l) were treated to determine the optimal hydraulic retention time (HRT) for each. Results showed that lower nitrate concentrations required shorter HRTs (3-4 hours) to achieve over 90% removal, while higher concentrations required longer HRTs (6-8 hours) for around 80% efficiency. Sulfate levels in the effluent remained below the guideline value of 500 mg/l, and pH levels did not exceed 8.8 due to the buffering capacity of limestone. The method offers a cost-effective and sustainable alternative for nitrate removal without external carbon sources or excessive sludge production.

Keywords: Autotrophic denitrification, Sulfur-limestone biofilter, nitrate removal, Wastewater treatment, hydraulic retention time