Abnormal opration of C.E.T.P.
Draining the sludge from aeration tank
If the sludge has accumulated in the aeration tank Is above the desired level ,
the excess sludge can be removed to the sludge drying beds. Stop the aerator and
allow the sludge to settle. This may be carried out once in 6 or 8 months.
No feed to Treatment Plant
If the feed to the treatment plant has be stopped due to same reasons , the operation
of the equalized wastewater transfer pump has to put off. The collection sump, the
wastewater will overflow the tank. When the treatment plant is ready to receive
the wastewater , wastewater collected in the holding (guard) tank can be pumped
into the plant.
Operational Problems
The concerned operators should record their observations and also day to day performance
including the flow, analysis of raw and treated wastewater power and chemical consumption
in a log book. Any abnormal observation should be brought to the notice of the person
in-charge.
Chemical Treatment
Lab studies should be conducted to optimize/ to check dosage carried out in chemical
Treated Area.
Biological Treatment
The operator should watch for changes in the physical appearance of the system and
relate those changes to the performance of the system. Observations can direct the
operator towards making more specific control tests that will indicate process demands
and determine the type and extent of control adjustments that will be needed.
Aeration Tank
The general appearance of the aeration tank contents has to be observed to determine
if there is any unusual or foam formation.
Mixed Liquor Color
Healthy sludge shows a light brown colour. A dark blackish colour may indicate anaerobic
condition caused by low oxygen or an improper discharge of sludge in the aeration
tank. This situation may require a check of influent flow into aeration tank and
control on sludge recycle.
If the condition persists for a longer period and affects the quality of treated
effluent, stock the feed to aeration tank and continue sludge recycle.
Fresh White Foam
A modest accumulation of fresh while foam is usually a good sign of well operated
system that is producing a good effluent.
Excess Billowing White Foam
Thick billows of white sudsy foam may indicate that the sludge age is too low and
requires an increase by reducing the sludge wasting rate. Stop the sludge wasting
if it is practiced. The presence of detergents or any forth forming compounds like
amines also may cause heavy foaming.
Initially , when the MLSS concentration in the Aeration Tank is less foaming may
be observed . However this will subside when the MLSS concentration in the Aeration
tank increases.
Thick Scummy dark Tan Foam
A dense and somewhat greasy and scummy layer of deep tan brown foam covering the
surface of the aeration tank may indicate an old sludge or one that is over oxidized.
To eliminate this , gradually increase the sludge wasting rate. Trends are Watched
until the difficulties are overcome and the process is restored to normal condition.
Measure the MLSS concentration and gradually waste the sludge and observe the changes.
Clarifier
If the Effluent is clear , it shows the prevailing control policies are adequate.
If the effluent is turbid , contains noticeable solids or is deteriorating steadily
, operating variables have to be reviewed.
Bulking Sludge
Bulking normally is attributed to the presence of filamentous microorganisms many
factors have been blamed for the development of bulking sludge like shock loadings,
ineffective aeration, nutrient imbalance and too low sludge age. Check the wastewater
characteristics to estimate the loading. Stop sludge wasting if the wasting is in
operation. Small dosage of chlorine at reduces bulking sludge.
De-flocculation
It is phenomenon where the sludge breaks up very small particles that settle very
poorly and treated wastewater becomes turbid. De-flocculation may occur because
of acid wastes, inadequate supply of nutrient and excess shear caused by hydraulic
turbulence . However , de-flocculation is normally a temporary phenomenon that will
correct itself over a period of time.
Rising Sludge
At times large masses of sludge will rise in the settling tank, burst and spread
over the surface. If the aeration is sufficient to produce nitrates in the aeration
tank and the dissolved oxygen level in the clarifier is not high enough, denitrication
may result. The oxygen associated with the nitrate is removed and the remaining
nitrogen gas rises to the surface carrying solids with it. Anaerobic conditions
eventually may develop and result in the beginning phases of digestion and gas production
. This also may cause sludge. When floating sludge appears in quantity on the clarifier
, stop the feed and continue sludge recycling till the flocs gradually disappear.
Taxic Materials
The material most commonly toxic to biological systems include lead, zinc, chromium
, copper, cadmium mercury, nickel ,cyanide , highly alkaline or acid discharges.
Oils, fats and greases are used by the bacteria for food but very slowly since they
tend to collect at the water surface , there is less contact between bacteria and
waste and longer break down is required. There materials will collect in the systems
and cause scum problems in process tanks if they are not removed in primary treatment
units.
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