The present work investigates nitrate and phosphate removal from synthetic treated slaughterhouse wastewater in a novel open raceway pond with sedimentation zone. For this purpose, microalgae Chlorella salina has been cultivated in synthetic wastewater and sedimentation zone has been added to enhance both algae separation in the system and nutrient removal. The effectiveness of Chlorella salina to treat nitrate and phosphate has been tested in open raceway ponds with harvest system. It has been found that Biomass concentration of the Chlorella salina is 1.35 g/L during 11 days of experiment. Also, maximum specific growth rate of the species in the pond has been 0.74 day-1. Throughout the cultivation period, nitrate and phosphate have been analyzed to show that their average removal efficiencies were 100% and 45%, respectively. It can be concluded that the growth of Chlorella salina in novel open pond system is an effective way to reduce nitrate and phosphate levels in slaughterhouse synthetic wastewater. Also, wastewater is suitable for algal growth.

River Ganga is one of the prime sacred National Rivers of India, closely associated with economic, social, and cultural heritage of Indian people. Recently, it has been subjected to immense degradation and pollution as a result of receiving huge amounts of domestic and industrial wastewater as well as religious ritual activities and surface runoff. The present study attempts to study spatial and temporal changes in water quality of River Ganga while calculating its Water Quality Index (WQI) by analyzing 9 physico-chemical, 7 trace metal, and 4 microbiological parameters at eleven sampling stations, on the basis of River Ganga index of Ved Prakash. Thus it can assess water’s suitability for drinking and irrigation purposes along with other human uses. The study is directed towards the use of WQI to describe pollution level in the river for a period of 1 year (from January to December 2014). It has been shown that index values as per CPCB class range between medium to good, while the ones as per NSF Index range from bad to good water quality. The study also identifies critical pollutants, affecting the river water quality within its course through the city. Finally, pH, DO, BOD, DO, EC, and FC have been found to be critical parameters for the stretch in each season of this research.

Groundwater plays a pivotal role as the largest potable water sources in Bangladesh. As agriculture is widely practiced in Bangladesh, potential nitrate (NO3¯) pollution may occur. Besides, excess amount of arsenic (As) has already been found in groundwater in many parts of Bangladesh including the present study area. Thus, this study was conducted to assess the NO3¯ status along with some trace metals and associated human health risk in the Central Bangladesh. A total of 99 groundwater samples were analyzed to assess human health risk due to high level of NO3¯ and other trace elements i.e. arsenic (As), iron (Fe), and manganese (Mn). Concentration of NO3¯ was determined using column chromatography and inductively coupled plasma optical emission spectrometer (ICP-OES) was used to measure As, Fe and Mn concentrations. It was found that the mean concentration of NO3¯ 253.17 (mg/L) in the groundwater samples exceeds the recommended guideline value by the WHO (50 mg/L). Moreover, this study area also characterized with elevated concentration of As (19.44 μg/L), Fe (811.35 μg/L), and Mn (455.18 μg/L) in the groundwater. Non-carcinogenic human health risk was calculated by justifying HQ (Hazard Quotient) and HI (Hazard Index) and attributed potential conjunctive human health risks due to NO3¯, As, Fe and Mn in the study area. Child (9.941) is more vulnerable than adult (7.810) considering non-carcinogenic human health risk. Moreover, high carcinogenic risk was found due to As contamination in the groundwater samples and children (1.94×10-3) are more susceptible to carcinogenic risk compared to adults (9.2×10-4).

Effective denitrification of water using photocatalytic reaction of active TiO2 particles doped with different oxides and metals has been the subject of numerous studies. For a particular research area, the potential of silica bond and its silicate based matrices with titanium dioxide and improving the photocatalytic performance using more economic methods is still challenging, and research in this field is attractive and ongoing. In this study, the effect of cement matrix and its complex bonds with industrial grade TiO2 particles was evaluated on the rate of water denitrification in a fixed bed circulating flow photoreactor. For this purpose, silica fume was substituted for cement in constant percent of 10 as a rich source of amorphous silica. Industrial grade TiO2 was added to the mix as5, 10 and 15 percent weight of cementitious materials (CM). Nano TiO2 was considered as a supplementary photocatalytic material with a constant 1% weight of CM in two mix designs. The results implied that the addition of 5% TiO2 increased the rate of nitrate concentration reduction by up to 10 times. Also, the specimen including 10% TiO2 increased denitrification rate by 107% compared to the previous content, which had much less impact. Also, the addition of nanoTiO2 increased denitrification rate up 113%.

Nitrate is a major contributor to water contamination, which can affect humans' and animals' health. Due to increased sewage production, growth of agricultural activities, and development of urbanization, recent years have seen an increase of Nitrate in water resources. Drinking water resources in both rural and urban areas of Jiroft City are supplied by water wells, scattered throughout the region. Thus the present research analyses the Nitrate pollution of 31 drinking water wells in summer and winter of 2016, in the urban area of ​​Jiroft City and by means of GIS as well as statistical analysis, presents the results as zoning and survey maps. It also studies and evaluates the effect of rainfall and soil type on the amount of Nitrate. Results from statistical analyses show that the amount of water pollution to Nitrate is independent from the type of land use as well as the soil type. Furthermore, statistical results show that the amount of Nitrate in the wells under test is affected by precipitation, being higher in the winter. Therefore, considering the agricultural density in this area and the untapped use of nitrogen fertilizers, it is necessary to take into account the use of chemical fertilizers for proper management, scientific and practical control, and maintenance of the wells' health safety.

Nitrate pollutants increase the growth of algal bloom, resulting in fresh water eutrophication. The high nitrogen level in wastewater has become a growing concern, which has risen the necessity to develop efficient nitrogen removal techniques. Biological denitrification, which is the reduction of oxidized nitrogen compounds like nitrate or nitrite to gaseous nitrogen compounds, is the most important and widely used method to treat nitrate wastes as it enables the transformation of nitrogen compounds into harmless nitrogen gas. As such, this study collected samples from Eutrophic Lake, picking isolates of bacterial strain with good growth rates in the nitrate medium. The selected bacterial strains were cultured on media 1and 2 and by means of UV-visible spectrophotometer, the nitrate removal efficiency and growth were detected at 410 nm and 600 nm OD respectively. After comparing three bacterial strains, it was found that RN1 had a higher efficiency in nitrate removal at 1000ppm nitrate concentration. At an optimum temperature of 37°C, pH of 7, and agitation of 121 rpm, after 432 hrs of the treatment, RN1 showed an optimum growth, equal to 0.1859 OD in 1000ppm nitrate solution with dextrose. Also the spectral analysis of RN1 strain showed 85% removal efficiency, thus making this strain the best one. Confirmed and identified as Bacillus species, it can be recommended for the bioremoval process of nitrate from wastewater.