Current online water quality monitoring methods and their suitability ...

5.3 Inorganic parametersThere are a number of inorganic ions that are required to be monitored in the PRW system to ensurethat its integrity is maintained. For example, fluoride is measured because it is an IPR contaminant ofconcern and may pose a health risk if not treated appropriately, whereas alkalinity needs to bemonitored as it is a COP point in Barrier 5 for water stabilisation and a critical point that may have animpact on Barrier 6. There are also additional parameters that need to be measured for compliancemonitoring purposes. The inorganic parameters required to be measured at each treatment barrierwithin the WCRW project are listed in Table 4.Table 4Inorganic parameters required at each treatment barrier within the WCRW project.Parameter B1 B2 B3 B4 B5 B6 B7 CommerciallyAvailableSodium √ √ √ √ YesPotassium √ √ √ √ YesFluoride √ √ YesCalcium √ √ √ √ YesIodide √ √ √Silica √ √ √CyanideAlkalinity √ √ √ √ YesSulphate √ √ √ √Chloride √ √ √ YesCurrently there are online commercially available sensors for most of these parameters, e.g: Hach: Alkalinity - colorimetric; sodium - ISE; Hardness (CaCO 3 ) – colorimetric; Fluoride ISE.There are other companies that also produce these online sensors. However it should be noted thatcurrently they are all based on standard laboratory methods. Therefore, these systems require frequentcalibration and regular maintenance, especially in Barriers 2, 3, 6 and 7 where the sample matrix canbe more changeable. Barrier 1 may also be problematic due to the nature of the sewer network andhighly turbid nature of the samples.Recommended: - Sodium analyser for Barriers 4 and 5.- Fluoride analyser for Barriers 5 and 7 (when fluoride is introduced into the SEQwater grid).Research and DevelopmentElectronic tongues offer a potential option for monitoring inorganic ions simultaneously and mayeliminate the need for multiple analysers. For example, Rudnitskyaya et al. (2001) 58 demonstrated thefeasibility of using an electronic tongue based on non-specific potentiometric sensors to determinesodium, chloride and calcium in addition to some heavy metals such as copper and zinc, with limitedsample pre-treatment being required. Guttierrez et al. (2008) 79 demonstrated using an electronictongue for measuring calcium, sodium and potassium, in addition to ammonium and nitrate ions. Thiscould be an option for online analysis in the future, which would reduce the number of analyserswhilst maximising the number of parameters that could be determined. This approach couldsignificantly reduce the costs and maintenance presently associated with online monitoring. However,issues associated with membrane fouling, signal drift and matrix interferences may still need to beaddressed, as the PRW system encompasses a diverse range of monitoring environments.√Current Online Water Quality Monitoring Methods and Their Suitability for the Western CorridorPurified Recycled Water Scheme Page 23