P5.2.1.6 Check strength of Supplier’s No supplier’s Check chemicals supplied certificate of certificate. calculations. Chemicals of and calculate analysis. poor quality. Elevated turbidity Adjust dilutions required Coagulant, and colour in dilutions for dosing. flocculant filtered and/or dose and as Calculation necessary. checks not signed chemicals. off. Dilution records. Check chemicals Change supplied for No supplier’s supplier. Supplier’s presence of certificate for certificate of significant chemical chemical analysis. contaminants. composition. Chemicals of Chemicals of possible potential health health significance significance exceed 50% of following their MAVs in the dilution. treated water. PARTICLES NOT REMOVED cont’d P5.2.1.7 that mixing of Coagulant, Elevated turbidity Review coagulant, flocculant and colour in treatment Inadequate flocculant and and filtered water. plant mixing of pHadjusting hydraulics to chemicals. Turbidity of water chemicals is chemicals. provide leaving the adequate over the improved Plant flow clarifier in the range of flow rates mixing of rate. range of 25 NTU. through the plant. chemicals. Turbidity. Post filter: turbidity is Colour. more than 0.2 Visual NTU inspection of colour is more floc stability. than 10 TCU Turbidity of aluminium clarified residual is more than 0.15 Frequency mg/L of filter elevated backwash. residual levels of other coagulants. P5.2.1.8 mixing times (See P5.2.1.7.) (See P5.2.1.7.) Review are adequate for treatment Insufficient effective plant contact time coagulation and hydraulics to for floc flocculation over the provide formation. range of flow rates improved through the plant, contact time and that carry over during to the filter is not coagulation excessive. and flocculation.
P5.2.1.6 Chemicals of poor quality. Check strength of chemicals supplied and calculate dilutions required for dosing. Supplier’s certificate of analysis. Coagulant, flocculant and chemicals. Dilution records. Supplier’s certificate of analysis. Chemicals of possible health significance following dilution. No supplier’s certificate. Elevated turbidity and colour in filtered Calculation checks not signed off. No supplier’s certificate for chemical composition. Chemicals of potential health significance exceed 50% of their MAVs in the treated water. Check calculations. Adjust dilutions and/or dose as necessary. Check chemicals supplied for presence of chemical contaminants. Change supplier. PARTICLES NOT REMOVED cont’d P5.2.1.7 Inadequate mixing of chemicals. that mixing of coagulant, flocculant and pHadjusting chemicals is adequate over the range of flow rates through the plant. Coagulant, flocculant and chemicals. Plant flow rate. Turbidity. Colour. Visual inspection of floc stability. Turbidity of clarified Frequency of filter backwash. Elevated turbidity and colour in filtered water. Turbidity of water leaving the clarifier in the range of 25 NTU. Post filter: turbidity is more than 0.2 NTU colour is more than 10 TCU aluminium residual is more than 0.15 mg/L elevated residual levels of other coagulants. Review treatment plant hydraulics to provide improved mixing of chemicals. P5.2.1.8 Insufficient contact time for floc formation. mixing times are adequate for effective coagulation and flocculation over the range of flow rates through the plant, and that carry over to the filter is not excessive. (See P5.2.1.7.) (See P5.2.1.7.) Review treatment plant hydraulics to provide improved contact time during coagulation and flocculation. significant
treatment-dissolved-air-flotation-feb14-v2.docx