kagal cetp
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.


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.


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.