Bangkok:

Wastewater Project

Description

Phase 1 of the Bangkok Wastewater Project covers an area of 38 km² in the central commercial district of the city on the east bank of the river Chao Phraya.

At present all buildings are drained by sewers in the streets discharching into the klongs (canals).

Rain water is collected by the same network.

437 interception points are to form the interface between the existing drainage network and the new facilities, there by limiting the system discharge to 5 times dry weather flow and allowing the excess flow during wet weather to drain to the klongs.

The conveyance system consists of four gravity sewer networks, which are to be constructed using trenchless techniques - i.e. by pipe-jacking or micro-tunnelling; each network will discharge to a 25 m deep interceptor which will convey the wastewater to the single treatment plant located at Mitmaitree Road in the Din Daeng District.

Altogether 866 manholes and shafts are to be constructed using mainly the caisson sinking method.

The treatment works will be fed by a pumping station equipped with 13 submersible units with a total capacity of 20 m3/s incl. three stand-by pumps.

After passing the screening and grit removal facilities the flow will gravitate for secondary treatment, while excess flow will be bypassed to the outfall.

Secondary treatment will be achieved using an activated sludge process with extended aeration carried out in aeration tanks with a diffused aeration system.

To achieve the required rate of nitrification and denitrification, the aeration tanks will have an anoxic zone followed by an aeration zone.

The treated effluent will pass through 15 clarifiers, where the sludge will be separated out, and then discharge to the outfall tunnel.

The sludge will be dewatered and transported to adigestion plant at a landfill area.

The consulting services are being carried out by DORSCH CONSULT (as lead firm) in association with another German and three Thai partners.