Page 547 - Industrial Wastewater Treatment, Recycling and Reuse

Zero Liquid Discharge Solutions 517

• Condensers designed with multiple passes to ensure high velocity and to
minimize scaling inside tubes
• Preheating of feed aid the process of stripping ammonia from the water.

13.5.3.1.4 Online Acid Dosing System After Stripper
An online acid dosing system is provided after the stripper to decrease the
effluent pH before it proceeds to the aerobic biological treatment system.

13.5.3.2 Sequential Batch Reactor (I and II)
13.5.3.2.1 SBR-I Feed Tank
Effluent from the pH correction tank is collected in the SBR-I feed tank, the
where it is retained for a sufficient period of time. The effluent is then
pumped to SBR-I from the feed tank.

13.5.3.2.2 Sequential Batch Reactor (ECOCAT-SBR)
The SBR uses an activated sludge process operated in batch mode with pre-
cise sequencing and control. The complete process takes place in a single
reactor. No additional settling unit or secondary clarifier is required. The
complete biological operation is divided into cycles, during which all treat-
ment steps take place.
A basic cycle comprises the following four steps:
• Fill and aeration
• Aeration
• Sludge settlement
• Clear liquid decanting.
Occuring in sequence, these phases constitute a cycle, which is then repeated.
The time required for each phase depends on the characteristics of the effluent.
During various phases, the operation of the equipment, such as the feed
pump, sludge recycle pump, air blower, and decanter, is controlled automat-
ically using on-off control valves, a variable frequency drive, and a DO
meter, with the help of a DCS/SCADA system (DO Meter - Dissolved
Oxygen Meter; DCS - Distributed Control System; SCADA - Supervisory
Control & Data Acquisition).

13.5.3.2.3 SBR-II Feed Tank
Treated effluent from SBR-I is decanted into the SBR-II feed tank, where it
is provided with adequate retention time. The effluent is then pumped to
SBR-II for further treatment.