Page 548 - Industrial Wastewater Treatment, Recycling and Reuse

518 Industrial Wastewater Treatment, Recycling, and Reuse

13.5.3.2.4 Sludge Thickener
Excess sludge from SBR-I and SBR-II is periodically pumped to the sludge
sump, which delivers it to the sludge thickener. The thickener is a hopper
bottom circular tank with a centrally driven mechanism where suspended
solids become settled at the hopper bottom and the clear liquid comes
out as overflow which is then recycled back to the SBR-I feed tank.

13.5.3.2.5 Thickened Sludge Sump
The thickened sludge from the thickener bottom is sent to the thickened
sludge sump.

13.5.3.2.6 Decanter
The thickened sludge from the thickened sludge sump is now pumped to the
sludge decanter for dewatering. The centrate from the decanter centrifuge is
again taken back to the SBR-I feed tank for further treatment. The
dewatered sludge is sent for further disposal.

13.5.3.2.7 Filter Feed Tank
Overflow from SBR-II is collected in this tank and provided with adequate
retention time. It is then pumped to the PSF and activated carbon filter
(ACF) via filter feed pumps.

13.5.3.3 Pressure Sand Filter
The filter feed pump transports effluent from the filter feed tank to the sand
filter. The suspended solids present in the wastewater get trapped in the sand
media, and clear water goes to ACF for further treatment. Online NaOCl
dosing is achieved via the inlet feed line to the activated carbon column. The
filter backwash water is then fed back into the SBR-I feed tank for further
treatment.

13.5.3.3.1 Activated Carbon Filter
The filtered water from the sand filter is fed into the ACF. Activated carbon
uses the physical adsorption process whereby attractive van der Waals forces
pull the solute out of solution and onto its surface. This filter helps to reduce
dissolved solids, color, and odor from the wastewater. The filter backwash
water is fed back into the SBR-I feed tank for further treatment. Outlet
parameters for this process are given in Table 13.7. Installation photographs
of the plant are shown in Figure 13.16.