Process Instruments (UK) Ltd.

Transcription

1 Process Instruments (UK) Ltd. Coagulation Control; Past, Present and Future Mike Riding Process Instruments (UK) Ltd.

2 What We Sell Biofilm ph Conductivity Dissolved Oxygen Free & Total Chlorine CRONOS CRIUS ORP TSS Chlorine Dioxide Ozone Streaming Current Particle Counter UV254

3 Coagulation The use of chemicals to make very fine particulates gather or clump together so they will settle out of the water and be of a more filterable size. - - Alum

4 Coagulation Mechanisms Charge neutralisation and destabilsation (Colloids and NOM) Complexation and precipitation (NOM) Enmeshment (Colloids) Adsorption (NOM)

5 Charge Neutralisation Al 3+ Soluble Cation Species e.g. Al(OH) 2+ Colloidal Hydroxide Precipitate Al(OH) 3(s) Amorphous Hydroxide Precipitate Al(OH) 3(am) NOM NOM NOM NOM Neutralisation / Complexation Microfloc Formation/ Adsorption Enmeshment / Flocculation

6 Parameters That Impact Coagulation Changes in: Coagulant Dose/Makeup Turbidity Organics Disinfection/Oxidation ph Temperature Physical

7 Coagulation Control in the past Manual Control ph Control Turbidity Control Streaming Current Control UV Control

8 Manual Control Jar Tester - Alum

9 Manual Adjustment Coagulant Pumped Coagulant Demand Manual Pump Adjustments

10 Chemical Feed Automatically Controlled Coagulant Demand Coagulant Pumped

11 Benefits of Automatic Control Improve Overall Plant Performance: Consistent, High Quality Finished Water Optimise Organics Removal Reduce Chemical Costs Reduce Soluble Aluminum Carryover Increase Length of Filter Runs Less Sludge Generated Less Sludge Disposal Costs

12 Coagulation Past and Present Single Parameter ph (Raw) ph (Post Coagulation) Turbidity (Raw) Turbidity (Settled) Streaming Current (Post Coagulation) Colour/UV254 (Raw)

13 Coagulation Control in the past Manual Control ph Control Turbidity Control Streaming Current Control UV Control

14 Dosing Alum Terrible soluble Best highest charge Floc little charge left

15 Coagulation Control in the past Manual Control ph Control Turbidity Control Streaming Current Control UV Control

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17 Coagulation Control in the past Manual Control ph Control Turbidity Control Streaming Current Control UV Control

18 Charge Neutralisation - - Alum

19 Charge Measurement Streaming Current Technology Reciprocating Piston Probe With 2 Electrodes Embedded In Annulus Colloidal/Ionic Adsorption High Flow Velocity Causes Ion Displacement Difference In Potential Arises Between Electrodes

20 Streaming Current Streaming Current responds immediately to changes in raw water conditions (e.g. turbidity, organics, flow). Measures what it is we are trying to do, which is neutralise charge. Feedback control. Gives immediate alarm if coagulant feed is disrupted or lost. By defining and controlling to an optimum setpoint streaming current value, coagulant dosage adjustments are made much faster and more reliably than jar testing.

21 Coagulation Control in the past Manual Control ph Control Turbidity Control Streaming Current Control UV Control

22 Using light absorption Many chemical compounds have specific absorbance characteristics at different wavelengths of light By measuring the light absorbed by a water sample at particular wavelengths, the concentration of a contaminant can be determined

23 Coagulation Optimisation

24 Coagulation - Past Multi Parameter ph (Raw) ph (Post Coagulation) Turbidity (Raw) Turbidity (Settled) Streaming Current (Post Coagulation) Colour/UV254 (Raw)

25 What should an automatic control system be? Modular yet bespoke (affordable) Multi Parameter (one at a time?) Capable of using existing plant instrumentation Affordable for smaller plants Simple (not sentient!)

26 Future Coagulation Control Controller Charge UV Turbidity ph Temp

27 Conventional WTP CRIUS UV254 NTU SCM ph/ Temp Cond.. UV254 ph Adj Coag Poly Cl MIXING FLOC BASIN SEDIMENTATION FILTRATION FINISHED

28 One size fits all?

29 Better Tools Laboratory Charge Analyser (Streaming Current) 5 Min Dosage Determination Clear End Point, No Risk Of Subjective Interpretation

30 Process Instruments (UK) Ltd. Thank you!

31 Jar Testing What is the standard test used in water treatment to determine the optimum coagulant dosage? By standard methods, 30 to 45 minutes to perform. More complicated as number of additives increases. Possibility of subjective interpretation.