sludge treatment process

8/15/2019 Sludge Treatment Process

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Sludge treatment process

What is sludge?

Sludge is semi-solid slurry and organic matter that produce and settle down in primary and

secondary sedimentation tanks from wastewater treatment processes. Sludge is commonly

disposed of by storing it in tank ( called a digester) where it will go through anaerobic digestion.

Sludge treatment process

Sludge treatment process consist of 3 stage which is thickening, digestion, and dewatering

1. Sludge tickening.

he sludge that comes out of waste water treatment has a higher water content. !n

sludge tickening, the content of sludge is increased by reducing the water content and

thickening means the process of reduction of moisture content of a sludge. hickening

process helps in reducing the capacity of digestion tank and pro"ides control of digestion

conditions.

#ra"ity thickening is one of simplest Ways to reduce the content of sludge by

using less energy. Sludge will be pumped directly into the round tank which

e$uipped with a slowly rotating rake which the function is to break the connection

between the sludge particles and therefore increase the settling and compaction. #ra"ity

thickening helps to reduced the total sludge "olume by e"en %&' from the original

"olume.nits of thickening are gra"ity thickener, floatation thickener and elutriation

thickener.



2. Digestion

igestion or stabili*ation is the reduction of organic content to a minimum.

+esides that, digestion phase helps in impro"ed drain ability and greatly reduces odor of

the pollutant matter. "erall reduction in the "olume of the sludge finally to be deposed.

naerobic digestion and aerobic are most commonly used processes for sludge

stabili*ation. ormally in this industry we will use anaerobic digestion.

naerobic digestiom is the process of con"erting sludge into another form of

matter which is li$uid and gases and also reduces the odor, "olume, putrescence and

produces biogas for energy supply. igestion takes place in one or se"eral reactors, and

the retention time of between /& and /0 days. he minimum retention time is around 12-

10 days that will cause lesser of gas production. he digestion reactor are e$uipped with a

miing and heating de"ices to guarantee good miing and constant temperatures. +acteria

like saprophytic organism are present that react on comple organic matter and

decomposed

emperature of anaerobic digestions consist of mesophilic digestions and thermophilic

digestion.

3. Dewatering

he sludge dewatering process is relati"ely simple4 increasing the dry solids

content of the sludge with different types of e$uipment. his unit process always re$uires

the use of at least some flocculant aid that keeps the ecess sludge flocculated in the

dewatering unit. Sometimes, coagulation chemicals such as iron or aluminium salts are

also added in order to enhance the efficiency of flocculant aids (polymers) and reduce the



consumption of them in sludge dewatering. Some research pro5ects are de"eloping

dewatering methods without any chemicals6 howe"er, the separation effect and reliability

are not yet sufficient (+altic sea region, /&10).

fter dewatering, the dry solids content of the sludge is usually between 1% ' and

3& '. epending on the dewaterabilty, it is possible to reach a dry solid content of up to

2& '. 7ethod of dewatering are di"ede to three which is sludge drying beds,

centrifugation and mechanical methods by "acuum filtration.

Sludge drying beds

rying beds are generally used for dewatering of well digested sludges. ttempst to air

dry raw sludge usually resultimg in odor problems. Sludge drying beds consist of

perforated or open 5oint drainage pipe laid within a gra"el base.

Uses of sludge

fter some treatment and process, sludge will turn to biosolid and sub5ected buffer re$uirements,

but not to crop har"esting restrictions.

sludge treatment process

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