4. Clarifier

4. Clarifier

The operation of the Clarifier is dependent upon the amount of settled sludge in the cone of the Clarifier and the performance of the jar test samples taken before the inlet to the Clarifier.
Before starting up the system, ensure the clarifier sludge is being directed back to the piping before the microscreen and not out to the lagoon.

The inlet jar samples will allow an operator to be able to determine if the chemicals are performing correctly, give an indication of the suspended solids at the Clarifier outfall, as well as allowing the operator to determine the appropriate sludge pump flow rates. The measurement of the settle sludge TSS from the three sludge valves located on the side of the cone allows an operator to be sure that the sludge pump is removing enough sludge from the Clarifier, so the solids don’t back up into the plate area and get carried over into the effluent.

Below are diagrams of Clarifier inlet jars that show correct settling of solids. The top portion of the liquid can be clear, grayish, yellowish or orange depending upon the amount of organics present in the manure. The liquid can be completely transparent to a murky translucent appearance. Normal readings for the supernatant liquid (liquid at the top of the inlet jar) can range from 0 – 800 ppm.


Below are diagrams of Clarifier inlet jars that show partially settled solids. The top portion of the jar can be clear, grayish, yellowish, or orange. There can be different levels of solids floating in the jar.
There can be small pieces of solids floating in the jar.



There can be a layer of solids floating on the top of the jar.
Info
Note: A few small pieces of solids floating on the top of the jar will not impact the operation and can be considered normal.


There can be a layer of solids floating on top the jar with a settled layer of solids on the bottom of the jar.

Info
Note: A few small pieces of solids floating on the top of the jar will not impact the operation and can be considered normal.




CLARIFIER WEIR TSS MEASUREMENT
Once liquid is flowing over the weirs at the top of the Clarifier, a TSS measurement should be completed. Typically, any TSS measurement under 1.5% of manure TSS and doesn’t cause rapidly increasing differential pressure across the cartridge filters is suitable for processing by the RO system. A TSS measurement that reads higher than 1.5% of manure TSS but doesn’t cause rapidly increasing differential pressure across the cartridge filter is suitable for processing by the RO system. If an increasing differential pressure across the cartridge filters is noticed, then additional chemical treatment is required – refer to the First Wave Manual to optimize microscreen operation.

CLARIFIER SLUDGE VALVE TSS MEASUREMENT
After the system has been in operation for 30 minutes and the system has stabilized, the sludge level in the sludge hopper will need to be assessed. A beaker of liquid is drawn off each valve (Top/Middle/Bottom) and the TSS is measured with the colorimeter. Open the valve and allow a small volume (300mL) to go to drain before taking the sample; this will allow the sample port to purge any liquids that may give a false reading. The TSS of the top and middle valves should be similar in concentration (+/- 200ppm). The bottom valve should have a TSS measurement that’s higher than the top two valves. The only exception to this is if the TSS at all three valves (Top/Middle/Bottom) are the same and are equal to the Clarifier weir TSS measurement.
Alert
Do not allow the TSS of the top valve to reach the same TSS as the bottom two valves. This means the sludge levels has risen to the top of the cone and solids are being carried over into the effluent. The Clarifier will need to have the plate area pumped out and the system reset.

CLARIFIER SLUDGE LEVELS RISING IN HOPPER
If the TSS at the middle valve rises beyond 200ppm of the top valve then the sludge levels are starting to rise in the hopper. The sludge pump flow rate should be checked against the inlet jar results to ensure it is set at the proper flow rate first. If the sludge pump is correctly set as per the inlet jar, then increase the sludge pump flow rate by 0.5gpm. Resample the inlet jar to ensure the Clarifier operation is stable and after 20 minutes resample the Clarifier sludge valves to see if the TSS at the middle valve has started to drop.


JAR TESTING CLARIFIER INLET WATER AND SLUDGE PUMP SETTINGS:

  1. Twice a day a jar of the water entering the fine solids separator should be taken and allowed to settle to measure how efficiently the separator is working and at what flow rate the sludge should be removed.
  2. A jar should be taken at the sample valve just prior to the separator inlet.
  3. The jar should be placed on a level surface and allowed to settle without being disturbed for 30 minutes. After 30 minutes the level of solids in the jar should be recorded in the log book and the TSS of the liquid above the solids should be measured and recorded.
  4. The screen filtrate flow rate will be required to set the sludge flow rate. The filtrate flow rate can be read directly from FQIT-1702B;
  5. The corresponding solids level indicates the flow rate that the sludge pump should be set at. i.e. A solids level of 1” in 5” is measured after 30 minutes with a screen filtrate flow rate of 10 gpm. By dividing 1” into 5” you get 0.2 or 20%. By multiplying the inlet water feed rate by the previously calculated percentage, you get the corresponding required sludge pump flow rate. So 10gpm * (0.2) = 2 gpm of sludge flow.
  6. The sludge pump flow rate is adjusted by adjusting the P-220 VFD. The minimum sludge pump VFD setting is 10Hz. Sometimes, the sludge pump flow rate is easier to adjust when the pump discharge has 25-30 PSIG of back pressure on it. The back pressure can be adjusted by throttling the discharge valve on the pump. Once the back pressure is set, then adjust VFD to set the flow rate.


CLARIFIER INTERNALS AND PLATE CLEANING:

  1. Some solids/scale will gradually build up on the vessel internals and separator plates. This will require periodic cleaning by the operator. The vessel should be cleaned ONCE A WEEK.
  2. The system will need to be shut down for the cleaning.
  3. Direct the clarifier sludge out to the lagoon and pump down the vessel until the level is below the bottom of the plates.
  4. Place boards across the top of the Clarifier to allow an operator to lift the plates out and set them on.
  5. Each plate should be pulled up half way and pressure wash both sides of the plate with a pressure washer to remove any solids. Once done fully remove the plate and place across the boards. During the cleaning and removal process, inspect the plate for damage.
  6. Once all the plates have been removed and set aside, use the pressure washer to wash down the vessel internals to remove any solids build up.
  7. Use the sludge pump to pump the washed off solids out of the vessel.
  8. Fill the cone half way up with clean water.
  9. After cleaning the plates they can be lowered carefully back into place.
  10. Restart the system.

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