Wastewater Treatment Trouble Shooting Guide

Cause and Effects of Microbially Related Activated Sludge Problems



Biological Oxygen Demand (BOD)/ Dissolved Oxygen (DO)

Cause of Problem

BOD of effluent corresponds to the amount of oxygen required for aerobic microorganisms to oxidize organic matter to a stable inorganic form.  When BOD levels are high, there is a decline in DO levels. The demand for oxygen by bacteria is high and they are taking oxygen from that which is dissolved in water. If there is no organic waste present in the water, there will be less bacteria present, and BOD will be lower and DO will tend to be higher

Effect of Problem

When BOD levels are high, dissolved oxygen (DO) levels decrease because the oxygen that is available in the water is consumed by the bacteria. Since less dissolved oxygen is available in the water, fish and other aquatic organisms may be stressed.

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Total Suspended Solids (TSS)

Cause of Problem

Undissolved or insoluble matter, floating or suspended in water, imparts a cloudy appearance  (turbidity) to it

Effect of Problem

Aside from its unpleasing aesthetic appearance, high TSS levels can harbour harmful bacteria, such as coliforms. These microorganisms can be fatal when ingested. They can readily attaché themselves on suspended solids, and are not readily disinfected.

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Blanket Rising

Cause of Problem

Denitrification in the secondary clarifier releases poorly soluble H2 gas which attaches to activated sludge flocs and floats them to the secondary clarifier surface

Effect of Problem

A scum of activated sludge forms on surface of the secondary clarifier and on aeration basin anoxic zones.

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Foam/Scum Formation

Cause of Problem

Undegraded surfactants and nocardiioforms, M.parvicella

Effect of Problem

Foam (scums) can float large amounts of SS to surface of treatment units; nocarioforms and M. parvicella foams are persistent and difficult to break mechanically; foams accumulate and can putrefy; secondary effluent SS can be elevated; foams can overflow tank freeboards

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Sludge Reduction

Cause of Problem

Many industrial and municipal wastewater lagoons have limited primary solids removal. In cold temperatures, digestion essentially stops.

Effect of Problem

Accumulations in the ponds can substantially reduce the hydraulic retention time and compromise effluent quality. Sludge accumulates in winter.

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Ammonia

Cause of Problem

Ammonia originates from protein deanimation resulting from bacteria breaking down the nitrogen-carbon bond of an amino group (R-NH3) BCP655

Effect of Problem

Presence of ammonia primarily in sludge processes

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Odours

Cause of Problem

Odor emissions are derived from the volatization of malodorous compounds found in the wastewater or formed most notably during the anaerobic decomposition of organic matter containing sulfur or nitrogen. These compounds include hydrogen sulfide, amines, mercaptans, disulfides and skatole.

Effect of Problem

The emission of specific, volatile malodour compounds depends on the wastewater characteristics and the treatment processes in use.

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Filamentous Bulking

Cause of Problem

Large amounts of filamentous microorganisms present bridge between the flocs or create diffuse flocs, interfering with compaction, settling, and thickening

Effect of Problem

HIGH SVI with very clear supernatant ; low RAS and WAS solids concentrations; in severe cases , the sludge blanket overflows the secondary clarifier; solids handling processes become hydraulically loaded

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