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Due to the extensive application of artificial nitrogen-based fertilizers and animal manure on land, many water agencies face problems of increasing concentrations of nitrate in groundwater. The contamination of groundwater by nitrate may pose a significant public health problem. The threat of methemoglobinemia is well documented and reflected in the US drinking water standard of 10 mg/L as nitrate-nitrogen. Approximately 45% of Saskatchewan's population use groundwater for drinking purposes, out of which, approximately 23% (230,000) are rural residents. The water used is made available from over 48,000 privately owned wells in regions where there is an extensive application of chemical fertilizers. Biological denitrification, ion exchange, and reverse osmosis (RO) processes were selected for a field study. Field studies were conducted on these processes. The sulfur/limestone autotrophic denitrification (SLAD) process was selected to achieve biological removal of nitrate from groundwater. The feasibility of the system was evaluated under anaerobic conditions. An ion exchange study was conducted using Ionac A554 which is a strong anion exchange resin. In the case of groundwater containing low sulfate concentrations, A554 offered high nitrate removal. However, the disposal of regenerant brine can be a problem. A reverse osmosis unit with Filmtec membrane elements (FT30-Element Family) was used in the study on nitrate removal. The unit effluent average nitrate concentration was less than the maximum allowable concentration.

A sulphur/limestone autotrophic denitrification process was used to achieve the biological removal of nitrate from groundwater. The feasibility of the system was evaluated under anaerobic conditions using laboratory-scale batch reactors. The optimum sulphur/ limestone ratio was determined to be 1:1 (wt/wt). Different initial nitrate-nitrogen concentrations (94, 57, and 10 mg NO 3 --N/l) were used during the batch tests to examine nitrate removal efficiencies. The results showed that the higher the initial concentration, the longer it takes before nitrate removal commences. Both total suspended solid (TSS) and mean size of particles increased with time, which may be related to bacterial growth in the system.

Fluoride concentrations in drinking water in excess of 1.5 mg L-1 are unsafe for human consumption. To reduce excess fluoride intake, developing countries must use low-cost, point-of-use defluoridation techniques. Although previous work has extensively assessed defluoridation using bone char (BC), most of the advanced studies have been based on the use of fluoridated distilled water as a feed solution. In the present study, BC columns were challenged with a range of model solutions, mimicking various pretreatment options. As a result, the relative impact of dissolved organic carbon (DOC) and suspended solids (SS) on the performance of BC filters was assessed. In addition, the performance of a gravity-driven, hollow fibre ultrafiltration (UF) module was examined with regards to the potential for use as a pretreatment option. SS were observed to severely clog the columns and cause the complete cessation of flow. The subsequent removal of SS by UF improved the general filter performance as well as increasing the BC lifetime by 50 %. The UF module achieved a reduction in DOC of 34 ± 6 %, resulting in an additional 30 % increase in the lifetime of the BC column.

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