HRSCC Clarifier Tank
High Rate Solid Content Clarifier ( HRSCC Clarifier Tank ) is used to settle the Sludge and separate from the clear treated water after Electro-Coagulation process. The Flash mixer forms an integral part of the HRSC Clarifier tank. The outlet water from the Lander of the HRSC Clarifier is clear, Colorless, and also with very low BOD and COD values. The Sludge collected at the bottom is pumped to a Sludge tank from where the sludge is handled by either centrifuge Hydro Extractor or Filter press.
Main use of HRSC Clarifier Tank
- To increase the faster settlement
- For sludge separation from the clear water
- To reduce the suspended solids very rapid level
- To improve the performance of the pressure sand filter
- To get crystal clear water in outlet
- To reduce the turbidity
LANGLIER SATURATION INDEX – LSI
- LSI is a method of reporting the scaling or corrosive potential of low TDS brackish water based on the level of saturation of calcium carbonate.
- LSI is important to boiler water and municipal plant chemists in determining whether a water is corrosive (has a negative LSI) or will tend to scale calcium carbonate (has a positive LSI).
- LSI is important to RO chemists as a measurement of the scaling potential for calcium carbonate.
- The LSI value is calculated by subtracting the calculated pH of saturation of calcium carbonate from the actual feed pH.
- The LSI value can be lowered by reducing pH by the injection of an acid (typically sulfuric or hydrochloric) into the RO feed water.
- A recommended target LSI in the RO concentrate is negative 0.2.
- A polymer-based antiscalant can also be used to inhibit the precipitation of calcium carbonate.
- Some antiscalant suppliers have claimed the efficacy of their product up to a positive LSI value of 2.5 in the RO concentrate (though a more conservative design LSI level is +1.8
- According to Reverse Osmosis, A Practical Guide for Industrial Users LSI is estimated as the difference between the current pH of the water ( pH ) and the pH at which calcium carbonate reaches saturation ( pHLSI ) :
LANGLIER INDEX LSI = pH – pHLSI , RYZENER INDEX RI = 2 pHLSI – pH
Where
pHLSI = (9.3 + A + B) – (C + D)
where
A = (log(TDS) – 1)/10
B = -13.12 * log( Temp(K)) + 34.55
C = log[Ca as CaCO3]
D = log [Alk as CaCO3]
| CONDITIONS | |||
| INDEX | NEUTRAL | TO SCALE | TO CORROSIVE |
| LSI | 0 | ABOVE 0 | BELOW 0 |
| RI | 6.8 | BELOW 6.8 | ABOVE 6.8 |
SILT DENSITY INDEX – (SDI)
- The SDI is a popular method for determining feed water quality in RO
applications.
- It is based on the time required to filter a volume of feed water
through a 0.45 μm filter pad at a feed pressure of 30 psig.
EQUIPMENT SETUP
- Assemble the test equipment per its drawing
- Locate a sample tap on the feed water piping and install the test
equipment.
- Adjust the pressure regulator to 30 PSI
- Use a fresh filter for the actual test.
NOTE : FOR BEST RESULT
- Use dull tweezers when positioning the filter to prevent puncturing
the filter.
- Ensure that the O-ring is clean and in good condition, and is properly
Positioned.
- Avoid touching the filter with fingers.
- Flush the apparatus to remove any contaminants that may be held
With in it.
SILT DENSITY INDEX – (SDI)
TEST PROCEDURE
- Take the temperature of the feed water. The temperature should not
vary more than + 1 °C between the start and end of the test.
- Bleed any entrained air in the filter holder. Depending on the model
of the filter holder, either open the bleed valve, or loosen the filter
holder while cracking the ball valve. Then close the bleed valve or
filter holder.
- Place a 500 ml graduated cylinder under the filter to measure the
amount of water that passes through the filter.
- Open the ball valve fully, and measure the time required to collect
100 ml and 500 ml* from the time the ball valve is opened. Record
these times, leaving the valve open for 5 minutes and letting the flow continue.
- After 5 minutes, repeat the time measurement required to collect 100
ml and 500 ml samples. Repeat again after 10 and 15 minutes of
elapsed time.
- If the time required to obtain a 100 ml sample is greater than about
60 seconds, pluggage will be about 90%, and it is not necessary to
continue the test.
- Measure the water temperature again to ensure that it did not vary
by more than 1 °C from the initial temperature.
- After completing the test and disconnecting the apparatus, the filter
paper may be saved in a plastic bag for future reference.
SILT DENSITY INDEX – (SDI)
CALCULATIONS
SDI = P30 / Tt = 100 * (1 – Ti / Tf) / Tt
Where SDI = Silt Density Index
P30 = % pluggage at 30 psig feed pressure**
Tt = Total test time in minutes
Ti = initial time in seconds required to obtain sample.
Tf = time required to obtain sample after 15 minutes (or less).
NOTES
- Time to collect 500 ml should be approximately 5 times greater than the time to collect 100 ml. If 500 ml collection time is much greater than 5X, SDI should be calculated using 100 ml collection times.
- For accurate SDI measurements, P30 should not exceed 75%. If P30 exceeds this value, re-run test and obtain Tf at a shorter time, (T).
- Hrscc clarifier tank is used in ETP
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