Nitrate Removal from Domestic Wastewater by Using Denitrification Limestone Filter

Abstract

Nitrogen is a naturally occurring element that is essential for growth and reproduction in both plants and animals. Excessive concentrations in the water body can cause excessive growth of algae and other plants, leading to accelerate eutrophication of lakes, and occasional depletion of dissolved oxygen. To remove nitrogen conventionally from domestic wastewater requires a high cost technology due to consumption of chemicals, high operational and maintenance cost. Therefore, an alternative low cost treatment technology particularly for nutrient removal including nitrogen removal system has been developed to improve the final effluent quality that is an aerated rock filter system. However, in the previous works in the UK the system was outperformed in removing ammonia nitrogen with limited nitrate removal. Hence, the present study was carried out to investigate the removal of nitrate from domestic wastewater through denitrification process using a lab-scale limestone filter. Domestic wastewater sample used in this study was collected from Taman Bukit Perdana Wastewater Treatment Plant (WWTP), Batu Pahat, Johor owned by IWK. The treatments were run in lab-scale limestone denitrification filter for 10 weeks. Effluent from nitrification filter was passing through the limestone denitrification filter as influent for further treatment. The in fluent and effluent of the filter system have been sampled and analyzed on biweekly basis for selected parameters including pH, alkalinity, temperature, dissolved oxygen, nitrate and ammonia nitrogen to monitor the effectiveness of the filter. Results from this study show that denitrification process has took place even the percentages of nitrate removal were considerably low but it seems promising with some modification of designing the the limestone filter to enhance denitrification process. The highest removal rate was 17.66%. Low removal of nitrate was inhibited within the filter system might be due to the high DO concentration as it was found that the range of DO was 4.75-7.78 mg/L. To permit the denitrification process to take place within the filter system, it is required an anoxic condition in the presence of nitrate with minimum DO concentration. Consequently, some modifications to the filter design will be considered in the future research in order to enhance the removal of nitrate through denitrification process.