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

Therefore online analysers that are prone to fouling, blockages, matrix interferences and signal driftmay not be suitable for this measurement barrier due to high costs associated with maintaininginstruments to obtain reliable data.Barrier 3Barrier 3 will use Micro-Filtration (MF), which is designed for the removal of viruses, bacteria andprotozoa with a minimum log removal efficiency of 3 Log 10. If treatment is successful, it will thenbe used as the feed water to Barrier 4, Reverse Osmosis (RO). Online analysers used in Barrier 3 mustoperate reliably in a relatively closed measurement environment with one defined entry and exit point.The online analysers will have to function reliably at the inlet where there may be source watervariations, and after subsequent pre-treatment steps will operate in a more controlled measurementenvironment than at Barrier 2.At Barrier 3, online analysers must have the following characteristics: Function reliably at the raw water inlet, in addition to the MF raw water and permeate. This isespecially important for Bundamba AWTP that will receive raw water from four WWTPswithin the scheme. Maintain their calibrated status irrespective of sample matrix conditions. For example, at theBundamba AWTP, analysers must be capable of functioning accurately in a changeablemeasurement environment, as the raw source water is derived from four different WWTPs. Operate reliably at low concentration levels.It is preferable for maintenance and calibration to be minimal, particularly as there are a number ofonline monitoring systems employed at this treatment barrier.Barrier 4Barrier 4 involves treatment using RO, which is designed to remove turbidity, organics, viruses,bacteria, and protozoa from the feed water through a molecular size exclusion process 9 . Once the ROpermeate is treated to the required specification it will be subject to Advanced Oxidation (AO) inBarrier 5 for the purpose of producing Class A + PRW. The online analysers operating in thismeasurement environment must be capable of reliable, high sensitivity measurements in a relativelyconsistent measurement environment, with one defined entry and exit point.Online analysers must have the following capabilities:Barrier 5Operate reliably in a high purity water matrix.Have adequate sensitivity for low level contaminants.It is imperative that sensors can function accurately and are capable of providing reliableinformation that can detect a decline in treatment performance or identify if a hazard iscompromising the system.Preferable for maintenance and calibration requirements to be minimal, as large numbers ofonline analysers are employed for operational monitoring purposes.Barrier 5 uses AO to produce water of a higher quality than conventional water treatment processes,and will remove trace organics, pathogens, viruses, and protozoa in addition to NDMA and 1,4-dioxane. The treatment process has one defined entry and exit point. Once the PRW has been treatedand the water stabilised and disinfected, it will be transported through the western corridor pipeline fortreatment in the natural environment (Barrier 6). It is very important for Barrier 5 to maintain itsintegrity, and online analysers must be capable of reliable, continuous measurements to monitor thequality of PRW produced before it is released to Barrier 6.Current Online Water Quality Monitoring Methods and Their Suitability for the Western CorridorPurified Recycled Water Scheme Page 8