The ADWG prioritises the removal of microscopic pathogens (and the toxins some produce) from public drinking water supplies to prevent large scale outbreaks of illness. This principle underlies the importance of adhering to consistently high standards of water treatment plant (WTP) operation and maintenance. This Guide refers primarily to the conventional WTP processes of chemical pre-treatment, coagulation, flocculation, clarification, filtration and disinfection; and establishes target criteria and critical limits for each step in the treatment process. The Guide is designed to provide water utility managers and operations staff with a concise reference document to optimising the WTP processes that produce microbially-safe drinking water and additionally supports the establishment of microbial Health-based targets.

Cyanobacterial blooms in surface waters are a source of cells, taste and odour compounds, and a range of toxins. This research optimised treatment processes for the removal and control of cyanobacteria and their metabolites from a range of source waters. It was concluded that pre-chlorination is not advisable when cyanobacteria are present, but that in some situation’s potassium permanganate is a viable alternative. Although all three tested coagulants; ferric chloride, aluminium chlorohydrate and aluminium sulphate (alum) removed 90 to 95% of cells, alum at pH 6.3 was the most cost-effective. Maintaining pH > 6 reduced cell lysis and metabolite release. Since cyanobacteria in sludge remained viable for 2-3 weeks it was recommended that sludge detention in the clarifiers should be minimised.