Event: LOSS OF PROCESS CONTROL (primarily coagulation, due to variation in the combined raw water/waste water composition). Possible hazards: Germs and health significant chemical determinands. Level of risk: Low–moderate P4.4.2.1 Routine controller Maintenance Maintenance Identify cause and pump log. log not signed of fault and Controller or maintenance off. rectify. pump schedule. malfunction Sudden (see Guide change in P10). coagulant demand. P4.4.2.2 Ensure Flow and rate of Coagulant Install flow reintroduction rate waste stream demand not proportional Rate of is proportional to reintroduction. proportional to controller. reintroduction the flow, not fixed flow rate. is not rate. proportional to the raw water flow. P4.4.2.3 Ensure coagulation Turbidity. Elevated Re-site dose control (eg, turbidity, coagulant Control of Colour. turbidity, colour, colour and dose control. coagulation Particle charge streaming current residual processes streaming – detector) sited so coagulant in does not take current. that it responds to filtered account of the the combined composition of stream, not just the the combined raw water. raw water and waste stream. P4.4.2.4 Avoid waste Colour natural Elevated Stop – treatment organic matter. reintroduction Poor or no conditions that of of waste control of Polymers/ contaminants stream. waste stream monomers. contaminants. in combined composition. Alter waste pH. raw water treatment. waste stream. Metals, Ensure waste Alter waste including Elevated treatment treatment. aluminium if coagulant adequately and used as the demand. consistently coagulant. Elevated separates solids Bacteria and coagulant from the aqueous protozoa. demand. phase using, for example, polymers, Turbidity, centrifuge, press, particle content. gravity thickeners. Colour natural – organic matter. Polymers and monomers. Metals, including aluminium if used as the coagulant.
Event: LOSS OF PROCESS CONTROL (primarily coagulation, due to variation in the combined raw water/waste water composition). Possible hazards: Germs and health significant chemical determinands. Level of risk: Low–moderate P4.4.2.1 Controller or pump malfunction (see Guide P10). Routine controller and pump maintenance schedule. Maintenance log. Maintenance log not signed off. Sudden change in coagulant demand. Identify cause of fault and rectify. P4.4.2.2 Rate of reintroduction is not proportional to the raw water flow. Ensure reintroduction rate is proportional to the flow, not fixed rate. Flow and rate of waste stream reintroduction. Coagulant demand not proportional to flow rate. Install flow proportional controller. P4.4.2.3 Control of coagulation processes does not take account of the composition of the combined raw water and waste stream. Ensure coagulation dose control (eg, turbidity, colour, streaming current detector) sited so that it responds to the combined stream, not just the raw water. Turbidity. Colour. Particle charge – streaming current. Elevated turbidity, colour and residual coagulant in filtered Re-site coagulant dose control. P4.4.2.4 Poor or no control of waste stream composition. Avoid waste treatment conditions that contaminants. Colour – natural organic matter. Polymers/ monomers. pH. Metals, including aluminium if used as the coagulant. Bacteria and protozoa. Turbidity, particle content. Colour – natural organic matter. Polymers and monomers. Metals, including aluminium if used as the coagulant. Elevated of contaminants in combined raw water waste stream. Elevated coagulant demand. Elevated coagulant demand. Stop reintroduction of waste stream. Alter waste treatment. Ensure waste treatment adequately and consistently separates solids from the aqueous phase using, for example, polymers, centrifuge, press, gravity thickeners. Alter waste treatment.
treatment-waste-liquor-reintroduction-feb14-v2.docx