BIOLOGICAL AND CHEMICAL TREATMENT OF WATER FOR COMBATING AMMONIA : AN INTEGREATED APPROACH

Abstract

Ammonia pollution in water has become a significant concern for environmentalists, chemists, and biologists due to the health hazards. The elevated nitrogen concentrations in the surface waters have primarily resulted from modern agricultural practices, mainly due to nitrogen fertilizers. However, the nitrogen discharge from the point sources, such as sewage treatment plants and industries, also contributes significantly to riverine nitrogen loading. Ammonia exists in the water in both organic and inorganic nitrogen. Organic nitrogen (ON) includes a wide variety of compounds; derived from natural and anthropogenic sources. The natural sources are principally nitrogenous end products of biological metabolism. Agricultural fertilizers also aid in the anthropogenic cause of organic nitrogen. Many bacteria, such as species of Nitrosomonas, possess the enzyme urease, which catalyzes the conversion of urea to inorganic nitrogen (IN) forms, like Ammonia (NH3) or ammonium ion (NH4 + ), that further oxidize to nitrite by the process of nitrification. The wastewater rich in ammonia nitrogen harms the environment significantly, as the ammonia nitrogen may inhibit natural nitrification, cause water hypoxia, result in fish poisoning, and decrease the water purification capacity. Removal of ammonia-nitrogen from water and wastewater is crucial for water and wastewater treatment operators because it produces potential carcinogenic disinfection by-products when contacting disinfecting agent chlorine. Disinfection by-products (DBPs), in addition to their likely carcinogenic nature, have an objectionable odor in drinking water, such as that of aldehydes and N-chloramines. When chlorine gas is added to water for disinfection, nitrogenous compounds convert to chloramines and are available in water in the form of combined chlorine. The formation of organic chloramines has increased chlorine demand in water and reduced the germicidal efficiency of chlorine and inorganic monochloramines. Organic chloramine includes the species of N-chloramines, N-chloramino acids, N chloraldimines and N-chloramides. Thus, water treatment utilities must have raw water quality that does not have ammonia-nitrogen contamination. Appropriate technology is necessary to accelerate nitrification by which ammonia-nitrogen can be converted to stable compound/s such that its adverse effects can be neutralized. This research focuses on the removal of ammonia-nitrogen from water and wastewater. The present study is based on treating two types of water. i.e., one of the Yamuna river water and second municipally treated sewage effluent. Yamuna river water has less ammonia than the municipally treated sewage effluent. The municipally treated sewage effluent (MTSE) samples were treated with cow dung sludge, yucca extract, and specific zeolites. Though, the v Yamuna river water samples were treated with zeolites only. A Jar Test Apparatus was used throughout the research experiments performed. The initial quality parameters of ammonia nitrogen, nitrite, and nitrate were determined before the experiment. Three types of zeolites were utilized in the ammonia-nitrogen treatment of MTSE samples and the Yamuna river water samples. Studies were also performed with synthetically prepared standard ammonium chloride water. Results showed that ammonia-nitrogen was significantly removed and converted to nitrate using cow dung sludge. MTSE samples had an initial ammonia nitrogen content of 34.78 mg/L when treated with 0.0 g/L (Control Sample), 1 g/L, 5 g/L (cow dung), and 100 mg/L, 500 mg/L (Yucca extract), respectively, reported conversion to 0.00, 0.00, 0.00, 0.00, 0.88 mg/L ammonia as-N; 17.8, 0.18, 0.09, 18.65, 18.85 mg/L nitrite as-Nand 21.8, 110.1, 133.5, 20.5, 20.8 mg/L nitrate as-NO3 respectively. It was found that digested cow dung acted catalytically in eliminating the ammonia nitrogen by converting it to nitrate in a short period of nearly eight days, leading to almost 100 % ammonia conversion. However, the yucca (plant) extract could not remove/ convert ammonia-nitrogen to any significant value. Based on the experimental results with cow dung sludge, a layout plan for the tertiary treatment of sewage effluents has been proposed in this thesis. All zeolites were observed to significantly treat ammonia-nitrogen in synthetically prepared ammonium chloride water without having competing ions interference. The sorption capacity of synthetic zeolite 4A was observed as 4.21, 7.68, 9.67, and 11.76 mg/g with 5.0, 10.0, 15.0, 20.0, and 30.0 mg/L ammonia nitrogen synthetic water. The ammonia nitrogen sorption with Clinoptilolite was observed as 3.82, 5.03, 7.09, 7.74, and 10.92 with 5.0, 10.0, 15.0, 20.0, and 30.0 mg/L ammonia nitrogen synthetic water. The removal capacity of Mordenite was found as 4.56, 5.24, 7.20, 8.29, and 9.85 mg/g with 5.0, 10.0, 15.0, 20.0, and 30.0 mg/L ammonia nitrogen synthetic water. However, because competing ions interfere in natural water, their use limits ammonium ions removal. In the case of the Yamuna-river water, ammonia sorption capacity and uptake (%) were observed with clinoptilolite as 0.212 mg/g and 23.24 % with an initial amount of 0.912 mg/L NH3-N and with mordenite zeolites as 0.42 mg/g and 37.5 % with an initial amount of 1.12 mg/L NH3-N. On the other side, when MTSE samples were treated with zeolites, sorption capacity and uptake (%) were observed. It was observed that with synthetic zeolites, sorption was 5.41 mg/g and uptake was 13.78 %; with clinoptilolite, sorption was 5.19 mg/g and uptake was 13.21 %, and with mordenite zeolites, sorption was 6.46 mg/g, and uptake was 16.45 % with an initial amount of 39.26 mg/L NH3-N. Based on the present study outcomes, this thesis suggested replacing sand media from Rapid Sand Filters and Slow Sand Filters with Mordenite and Clinoptilolite.