BIOLOGICAL NUTRIENT REMOVAL FROM WASTEWATER BY USING SINGLE SBR AND WATER HYACINTH

Abstract

Nowadays, environmental legislation has become more restricted in the nutrient wastewater discharge, especially in the sensitive areas and vulnerable zones. Wastewater treatment technology is posing serious techno-economic problems in cities, particularly in developing countries. So, many studies have been stimulated on the understanding, developing and improving the biological nutrient removal processes. In this dissertation work, the two different methods of treatment have been studied for Saharanpur municipal wastewater. (1) Single Sequencing Batch Reactor (SBR) Process. (2) Purification by water hyacinth (Eichhornia crassipes). - In the SBRs process, aeration was provided by diffused air devices which have the added advantage as mixers or aerators. In this process aerobic digestion by bacteria occurs in the presence of oxygen. Under aerobic conditions, bacteria rapidly consume organic matter and convert it into carbon dioxide. This technology used though appears to be simple yet still achieves a high degree of Biological Nutrient Removal (BNR). The process used in laboratory is a single tank Sequencing Batch Reactor (SBR). The results from the laboratory work are excellent but have to be confirmed in the pilot plant studies. It was found that a certain degree of anaerobic pretreatment can reduce part of the carbon concentration most efficiently while still leaving sufficient Chemical Oxygen Demand (COD) required for successful BNR. Medium-to-low strength wastewater has been supplied in SBR. This was operated with different FILLING/REACTION time ratios. During Filling, fermentation reactions probably occurred and this resulted in up to 86% reduction of the initial dissolved BOD5 concentration. Degradation of waste then continued into the Reaction period. This preliminary assessment showed that the SBR is, potentially, a viable option for wastewater treatment, especially since the aeration time required for treatment to achieve the effluent quality is small. The SBR was operated for 4 months for treating the "Municipal wastewater". In order to have a mixed culture, the system should be able to perform carbon oxidation, nitrification, de-nitrification and biological phosphorus removal. Despite high influent concentrations of approximately 58.40 mg L' N and 4.56 mg L' total P, good effluent quality of less than 1 mg L' N and less than 1 mg L1 total P and high removal of BOD, COD, and TSS in the range of 94.57, 92.12, and 88.34% has been achieved. Furthermore the operation of the small SBR systems has proved to be simple and reliable. - Wastewater purification by water-hyacinth (Eichhornia crassipes), is a relatively new possible solution. This floating plant has been used in aquatic systems for wastewater purification for many years worldwide. A lot of interests have been shown for this plant in last few years in India (Aoi T. et al., 1996). In this study the suitability and effectiveness of water-hyacinth in treating Municipal wastewater has been analyzed. A 28-days experiment was performed in natural conditions. Several parameters were measured and analyzed, including the Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), ammonia and phosphate contents, pH value, DO and turbidity. Laboratory analyses indicated that the water-hyacinth culture drastically reduced the BOD from 101.67 to 31.71 mg L, COD was reduced from 505 to 264.08 mg L' and pH value fell slightly from 7.19 to 6.87. Results obtained from our studies and other papers in using water hyacinth and aquatic systems have been analyzed. These studies and scientific papers also describe this plant as notorious weed and propose different control measures. The final effluent from water-hyacinth could be used for irrigation and recycled to a flowing stream for other uses except for drinking purposes.