In table 2.5 was shown the data for MLSS

In table 2.5 was
shown the data for MLSS and in figure 3.8 was illustrated the relationship
between the Mixed liquor suspended solids (MLSS) and  Days of the sample.From the graph was shown
the pattern of the graph was decreased and just at certain days the value of
MLSS was the increase.This is because the suspension of microorganisms was increased
and at the optimum phase which is at third days and the amount is 31mg/L.There
are some errors during this treatment which is the machine was stopped suddenly
for the whole days at sixty days, so it will affect the amount of mass which is
213mg/L that the return pump cannot flow the suspended solids from settler into
the aeration tank.According to the theory, it supposed to decrease which is the
lower the amount of MLSS, the longer the times. (Maine et al., 2013) . 

 

From the source
of USEPA,1999 stated the range of MLSS, mg/L for conventional activated sludge
is around 1500-3000mg/L. From the table 2.9 was shown the highest value of MLSS
is 345mg/L and not around the range of USEPA.it is because the concentration of
raw wastewater was low so the suspended solids that produced also decrease.It
should also be realized that as the MLSS concentration increases, the rate at
which the MLSS will settle in the secondary clarifier actually decreases. The
slower rate of settling, due to a higher MLSS concentration, can then lead to a
higher total suspended solids concentration leaving the clarifier.(Eddy et al.,2014).   

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One rule of thumb
for activated sludge systems is that for every pound of BOD removed in the
secondary system a half a pound of new solids is generated through the
reproduction of the organisms and addition of new organisms from the influent
wastes. If the MLSS concentration is above the desired concentration, wasting
of the excess solids will have to be started or increased. If the MLSS
concentration is below the desired concentration level, wasting should be
decreased or stoppedIncreases or decreases in wasting should be made gradually
around 20 – 25 percent per day. (Tauqeer, 2013)

 

5.2.4 Mixed  liquor Volatile suspended solids (MLVSS)

 

Mixed Liquor
Volatile Suspended Solids is a test for the amount of volatile suspended solids
found in a sample of mixed liquor.Volatile solids are those solids which are
burnt up when a sample is heated to 5500C. Most of the volatile solids in a
sample of mixed liquor will consist of microorganisms and organic matter.As a
result, the volatile solids concentration of mixed liquor is approximately
equal to the number of microorganisms in the water and can be used to determine
whether there are enough microorganisms present to digest the sludge enough microorganisms
present to digest the sludge. (Dharaskar et al., 2015)