Greater Sydney Filtration Plants Enhanced Coagulation Jar Testing for NOM Removal
In response to changing raw water profiles across the Greater Sydney catchment, CWT undertook an extensive jar test research project investigating the potential for Enhanced Coagulation (EC) to improve the removal of NOM for the Nepean, Woronora and Illawarra WFPs.
- Raw water analyses on the Nepean, Woronora and Illawarra raw water sources
- Replication of current WFP ferric chloride and coagulation pH conditions for each WFP
- Identification of the optimal EC ferric chloride dose and pH for each WFP
- Investigation of the impact of PAC addition and contact time on NOM adsorption for each WFP
- Investigation of disinfection byproduct and THM formation potential for each WFP
- Coordination with external laboratories for the analysis of organic speciation via rapid fractionation and HPSEC, DOC, and THMs.
The Nepean, Woronora and Illawarra WFPs are direct filtration processes with limited scope to operate for prolonged periods under elevated filter stress which typically rules out EC as a treatment option for the removal of NOM. However, if the Illawarra, Woronora and Nepean WFPs were upgraded by the addition of a high rate settling process, such as an Actiflo clarifier, then EC could be applied and the removal of NOM expected to improve by a significant amount. Further, the application of twin Actiflos with the first unit operating in EC mode and the second in the ActifloCarb process with recycled PAC, would be expected to achieve a large additional reduction in NOM.
To achieve this CWT undertook an extensive jar testing program targeting maximum NOM reduction, simulating the respective current WFP treatment processes against the NOM removable achievable using both EC alone as well as EC followed by PAC dosing.
The results and recommendations of the study allowed Veolia and Sydney Water Corporation to make informed planning decisions regarding future WFP augmentation needs for the three sites while also informing of the current optimal operating conditions.