Reaction kinetics and validity of BOD test for domestic wastewater released in marine ecosystems

With urbanization of coastal cities, marine pollution is becoming a severe problem. The rates of biodegradation, decomposition, and ratification of pollutants get slowed down due to salinity. The higher temperatures prevalent in tropical regions significantly affect reaction rates. Multiple factors influence the rate of biodegradation, making the process complex. Hence, prediction and evaluation of the assimilative capacity of the marine environment due to wastewater discharges is becoming a difficult task. Biochemical oxygen demand (BOD) is a wet oxidation process, which follows first-order kinetics. The values of kinetic rate constants are expected to differ with varying salinities and temperatures. Research is carried out using glucose-glutamic acid and domestic wastewater to evaluate the impact of salinity on biodegradation of carbonaceous waste at 20°C and 27°C. The findings confirm the hypothesis of slow biodegradation of carbonaceous organic matter in marine waters. An inverse relationship between rate of biodegradation and salinity was observed. BOD exertion at 20°C (5?days) and 27°C (3?days) for the marine environment is comparable at selected salinities thereby confirming the validity of BOD test of shorter duration at elevated temperature.     

Arsenic contamination of groundwater in the Terai region of Nepal: an overview of health concerns and treatment options

A review of published information on the arsenic contamination of groundwater in the Terai regions of Nepal showed that the source was mainly geogenic due to the dissolution of the arsenic-bearing minerals. Clinical observations of patients in the arsenic affected districts revealed chronic arsenic poisoning from drinking water. Half a million people inhabiting the region are believed to have been exposed to arsenic levels greater than 50 microg/L in their drinking water. Thirty-one percent of the population (3.5 million) in the region are estimated to have been exposed to arsenic levels between 10 and 50 microg/L. Iron assisted biosand filters currently distributed and in operation are a suitable alternative to mitigate the interim arsenic standard of 50 microg/L, as set by the Nepal Government. Arsenic biosand filters were also effective in removing bacteria and viruses from drinking water in laboratory and field tests. However, groundwater treatment targeting cluster communities in the Terai region is the sustainable way of mitigating the arsenic problem.     

Assessment of water quality using multivariate statistical techniques in the coastal region of Visakhapatnam,India

The present study was intended to develop a Water Quality Index (WQI) for the coastal water of Visakhapatnam, India from multiple measured water quality parameters using different multivariate statistical techniques. Cluster analysis was used to classify the data set into three major groups based on similar water quality characteristics. Discriminant analysis was used to generate a discriminant function for developing a WQI. Discriminant analysis gave the best result for analyzing the seasonal variation of water quality. It helped in data reduction and found the most discriminant parameters responsible for seasonal variation of water quality. Coastal water was classified into good, average, and poor quality considering WQI and the nutrient load. The predictive capacity of WQI was proved with random samples taken from coastal areas. High concentration of ammonia in surface water during winter was attributed to nitrogen fixation by the phytoplankton bloom which resulted due to East India Coastal Current. This study brings out the fact that water quality in the coastal region not only depends on the discharge from different pollution sources but also on the presence of different current patterns. It also illustrates the usefulness of WQI for analyzing the complex nutrient data for assessing the coastal water and identifying different pollution sources, considering reasons for seasonal variation of water quality.