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Wastewater Suspended Solids - The 4 Types & How to Measure Them

In this article I explain in brief about what solids are in suspended form in wastewater and how they are measured.
I have also given a range of values for the wastewater suspended solids found during the activated sludge process for a quick comparison of test results.
Mixed Liquor Suspended Solids (MLSS) The MLSS is the amount of solids present in a mixed liquor containing wastewater.
This liquor contains both forms of wastewater suspended solids, namely the organic solids as well as those that are in mineral form.
Microorganisms are also found in this liquor.
Hence, while estimating the quantity of solids present in suspended form, the dried concentrate of the wastewater suspended solids is weighed.
To calculate the weight, first an aliquot of the mixed liquor is filtered.
It is then dried at a temperature of 105 degrees C.
Once completely dry, it is weighed.
Range Of Values Of Mixed Liquor Suspended Solid Particles In Activated Sludge Conventional = 1,500 - 3,000 MLSS (mg/l) Step Aeration = 2,000 - 3,500 MLSS (mg/l) Extended Aeration = 3,000 - 6,000 MLSS (mg/l) Pure Oxygen System = 6,000 - 8,000 MLSS (mg/l) High Rate Aeration = 4,000 - 10,000 MLSS (mg/l) Mixed Liquor Volatile Suspended Solids (MLVSS) If the mixed liquor contains concentrations of particulate solids then the mixture is called as MLVSS.
It is the same as MLSS, except that the organic wastewater suspended solids in that liquor is considered as the volatile part and is then called as MLVSS.
This part consists of microorganism living and dead, the non microbial organic forms, and the debris of the cellular organisms.
Dried samples of the solids are used to determine the value of MLVSS.
The concentrate is obtained by filtering the wastewater and then drying them at a temperature of 600 to 650 degrees C.
The ratio of MLVSS to MLSS for activated sludge is in the range of 0.
65 to 0.

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