Dewatering, waterproofing and drainage - Tunnel Engineering: Basics and Additional Services for Design and Construction - page 204

Table 5-12 Water treatment equipment [62].

Underground Above ground

Transportable settling basin
Intermediate pump sump as a
settling basin
Main pump sump with upstream
treatment basin for settlement
Use of a vacuum suction vehicle

Mechanical process: settling basin

Chemical process: precipitation,

neutralisation

Sludge treatment: chamber filter press

Monitoring equipment: pH meter,

quantity measurement

Underground treatment facilities. Fig. 5-11 shows a possible layout of an underground
treatment plant. The water collected at the face passes through many successive transport-
able settling basins in order to make use of the potential for separation of solids in the tun-
nel. The intermediate pumping sump and the main pumping sump also provide settlement,
and a simple sheet steel container can be equipped as an initial settling basin. The settled
sludge must be cleaned from the basins daily by a vacuum suction vehicle.

Figure 5-11 Main pump
sump underground [62].

Treatment facilities above ground. The design of a treatment plant above ground (Fig.
5-12) should be based on the following constraints:

- Max. water inflow in l/s.
- Stay time at max. throughput.
- Construction of at least two settling basins, which can be operated independently (in
order to clean one of the basins).
- Consideration of other process stages depending on the required cleaning effect (pre-
cipitation, neutralisation, sludge dewatering).