Sanitation Value Chain adopted in Tamilnadu and the way of the Technology suitable for the Sludge Treatment

 

Sanitation Value Chain

The five things that are covered under the sanitation value chain are

1) User Interface

2) Collection/Storage/Treatment

3) Emptying and Conveyance

4) Treatment

5) Use and/or Disposal

 

 

 

 

 

Figure 2: Five Groups of the Sanitation Value Chain

Introduction of the Functional Groups of a Sanitation System

(A) User Interface

Four kinds of user interfaces are poured flush toilet, cistern flush toilet, urine- diverting dry toilet and composting toilet.

(B) Excreta Storage

Twin pits, septic tanks and biogas digesters are used for the storage, collection and treatment of excreta.

(C) Options for Removal and Transport of Faecal Sludge and Septage

          Manual and mechanized techniques like hand tools, vacuum trucks, pumping systems or mechanical augers can be applied for the removal of FS. Four most common types of manually operated mechanical pumping equipment, i.e., the sludge gulper, the diaphragm pump, the nibbler and the manual pit emptying technology may be developed. Fully mechanized technologies such as motorized diaphragm pumps, trash pumps and some types of vehicle-mounted vacuum equipment are powered by electricity, fuel or pneumatic systems

(D) Treatment Technologies for Effluent and Sludge

Before treatment of FS (which is discharged by collection and transport trucks), a preliminary screening is needed for most treatment technologies because of the presence of high content of coarse waste such as plastic, tissue and paper. The treatment part is divided into four steps:

(1) primary treatment (separation of solids and liquids)

(2) Treatment of solid part/sludge (solid which is generated from the primary treatment)

(3) Treatment of liquid part/ effluent (liquid which is generated from the primary treatment) and

(4) Treatment of post-effluent (final treatment of the liquid part).

After treatment, three types of end products will be produced, i.e., screenings, treated sludge and liquid effluents.

Step 1: Technology for Primary Treatment (solid–liquid separation)

          The technologies used for primary treatment are unplanted drying bed (UDB), planted drying bed (PDB), anaerobic digester (AD), centrifugation, settling-and-thickening tank (S&T), Imhoff tank (IT), anaerobic baffled reactor (ABR), belt filter press (BFP) and geobags. After primary treatment, the sludge is removed from the bed manually or mechanically and is used as manure by co-composting. Sludge cannot be used directly as an end product due to the presence of pathogens, and so Step 4 is needed for the final treatment of sludge.

Step 2: Technology for Effluent Treatment (liquid part treatment)

          A liquid part would be produced after primary treatment. This is a partially treated liquid, which needs further treatment before disposal. The technologies used for effluent (liquid) treatment are waste stabilization ponds (WSPs), activated sludge process (ASP), sequence batch reactor (SBR), membrane bioreactors (MBRs), anaerobic filter (AF), anaerobic baffled rector (ABR) and constructed wetland (CW).

Step 3: Technology for Post-Effluent Treatment/ tertiary treatment

          The technologies used for post-effluent treatment are chlorination and ozonation. Post-Effluent Treatment stage is the final treatment of effluent/ liquid which is generated from effluent treatment plant.

Step 4: Technology for Sludge Treatment

          A solid part would be produced after primary treatment. This is a partially treated solid, which needs further treatment before disposal. The technologies used for sludge treatment are composting, vermicomposting, deep row entrenchment, shallow trenches, solar drying, solar sludge oven, lime stabilisation and sludge drying bed. This is the final stage of treatment of biosolids before discharge.