The goal of this paper is to review the technologies used for nitrate removal from water intended for human consumption. It also reviews the effects of nitrates on human health and the various legislative provisions in different states. The treatment technologies that will be detailed are: reverse osmosis, ion exchangers, biological denitrification and electrodialysis. For every technology, the following information will be provided: advantages, disadvantages, process performance and cost. Furthermore, there will also be examples of water treatment plants across the Globe that use these types of technologies for nitrate reduction.
Ammonium is an inorganic compound present in water at pH<9. Ammonium has no toxic effects on human health, but its presence in water can indicate a water pollution. The presence of ammonium in groundwater source can be largely determined by the reducing conditions from the aquifer, while in surface water sources it is found only in polluted waters. In water supply systems, the presence of excess ammonium in raw water is not desirable because it can generate problems such as: unpleasant odors, microbial development in the water distribution system, reducing the efficiency of chlorine disinfection and increased chlorine consumption. Over time, several methods have been developed to reduce the concentration of ammonium from water, these being physical, chemical, biological or a combination of these methods. The article presents a review of the technologies currently used to reduce /oxidize ammonium from water. These mainly includes: ion exchange and adsorption, biological filtration, air stripping, breakpoint chlorination and reverse osmosis.
Diffuse pollution is a major source of contaminants to surface waters in urban areas. Land use activities and the degree of imperviousness have a strong influence on the pollutant loadings and the pattern and distribution of the pollutograph. Uncontrolled discharges of contaminated urban storm water runoff contribute to impairments of water quality in receiving waters. In this study, grab samples of storm water runoff were collected from a small high-density residential catchment area in Bucharest. The pollutant concentrations were analysed for several water quality physical and chemical parameters including pH, conductivity, oil and grease, nutrients, pathogen indicator bacteria and some heavy metals. The storm events were monitored through grab sampling. The sample results for this representative residential catchment area in Bucharest were then compared with data reported from other regions of the world. The analysis demonstrates that the characteristics of the urban runoff quality from residential areas in Bucharest were comparable with data obtained from other areas in the world.
Wastewater treatment of the food industry by using a combination of the anaerobic-aerobic process as a pre-treatment and the bioreactor treatment represented by MBR system has been proven as an efficient single step process to treat industrial wastewater and produced an excellent effluents quality suitable for reuse. In this study, three phases of anaerobic biodegradation were used as the first step of biological pre-treatment, with the time of fermentation 5, 10 and 15 days respectively. At each phase, the aerobic biodegradation process was performed to activate sludge at periods of 2, 4, 8, and 24 hours, respectively, with the MBR system using hollow fibre membrane type ZW-10 that's operating under a low-vacuum. NaOCl solution has been adding in the bioreactor tank during the backwashing process. Twenty-eight of samples were collected from the influents and the effluents during the biological and bioreactor treatments. The samples were tested for eight water quality tests: temperature, Dissolved Oxygen (DO), pH, Turbidity, Total Suspended Solids (TSS), Mixed Liquor Suspended Solids (MLSS), Chemical Oxygen Demand (COD), and Biochemical Oxygen Demand (BOD5). The results indicated that the bioreactor system can be used efficiently to treat the effluent of food industry from meat processing. The results of the first phase PI (after 5 days of fermentation) considered as the best phase, which provided the excellent removal efficiency of TSS, BOD 5 , and COD to reached 98.31%, 94.53%, and 95.56% respectively at HRT 24 h.
The overall aim of this search investigated the effect of DO, alkalinity, and pH on nitrification in biological aerated filter system BAFs. The laboratory experiments by three identical pilot-scales downflow of BAFs using three different sunken materials types, 0.78±0.60 mm activated carbon-based material bed, 0.95±0.58 mm sand-based material bed, and 3.28±2.14 mm ceramic particle-based material bed, as attached growth zone in the treatment of municipal wastewater. As results of the experiments showed that activated carbon-based material bed when the mean concentration of dissolved oxygen was 6.76±2.25 mg/L and the mean alkalinity concentration was 77.25±2.60 mg CaCO3/L and the mean pH value was 7.21±0.20 the mean nitrification efficiency has reached of 90.11%. In the sand-based material bed when the mean concentration of dissolved oxygen was 7.33±1.82 mg/L and the mean alkalinity concentration was 77.56±2.77 mg CaCO3/L and the mean pH value was 7.22±0.20 the mean nitrification efficiency has reached of 87.74%. In the ceramic particle-based material bed when the mean concentration of dissolved oxygen was 6.37±1.84 mg/L and the mean alkalinity concentration was 77.31±2.71 mg CaCO3/L and the mean pH value was 7.22±0.20 the mean nitrification efficiency has reached of 85.17%.
The removal of nitrogen compounds in wastewater is receiving wide attention and the effluent standards will be tougher in the near future. The overall aim of this article is a review of biological aerated filter systems BAFs for removal of the nitrogen in wastewater. The BAFs technology is based on the principle of biofiltration where can be operated either in an upflow or downflow mode depending upon the position of the influent feed, where the media which attached growth zone can be either denser than water to give sunken media or less dense than water to produce floating media. The BAFs combines biological treatment and ammonia-nitrogen and solids removal in one reactor unit, where accumulated solids are removed from the BAFs through backwashing.
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