Polishing/Tertiary Plant
Process Descriptions


The pre-treated water is pumped to the aeration pond. In the pond, the BOD and COD is re-aerated with a surface aerator.

The pre-treated water is pumped with controlled flow from the aeration pond to the polishing unit.

In the reaction and flocculent tank, coagulant and polymer is added to get an optimal flocculation and separation of particles during agitation.

Equipment: Agitators is running continuously. Dosing pumps for coagulant and polymer is running when the Inlet pump is running.

In the Lamella Separator the sludge will be separated.






Sludge pump will be operating with Paus-running time when the Inlet pump is running.

The sludge will be pumped to a 2 phase decanter to separate water from the sludge.

The overflow flow from the Lamella Separator is running by gravitation to the continuous Sand Filter. In the Sand Filter the waste water is filtrated.

The Sand filter is a continuously operating filter. The fluids flow through a sand bed in which suspended particles are trapped. Purified filtrate is removed above the filter bed. Small amounts of contaminated filter sand is pumped from the bottom of the filter, to a washing device, and then returned to the top of the filter bed. This in effect, moves slowly downwards while the fluid passes upward through the filter.

The filtrated water runs by gravitation from the Sand filter to UF-feed tank.

The filtrated water is pumped to the ultra-filtration unit. The level control in UF-feed tank start and stop the pump.

Continuous backwash sand filter

Continuous backwash sand filter

Lamella Clarifier



Ultra Filtration Unit


In the ultra filtration unit the final polishing of the waste water is done. The ultra-filtration unit is equipped with 24 filter units. 16 units are always in operation. 8 units are running in an automatic CIP sequence. This means that we always are running a clean ultra-filtration unit, without clogging problems.

The clean water is delivered to the Clean water tank.

From the Clean water tank, the water is pumped to outlet.

The tank is also working as a buffer tank for the back wash of the filtration unit. The Backwash pump is stopped at low level in the tank.

The reject water from the ultra filtration unit and Sand filter is send to a sump in the floor, to be sent back to the aeration pond.

* Click the following graph for larger view

PID Sketch

Polishing Plant for 30M . HR Capacity

P&I Drawing & Schematic Plant Layout

Schematic Layout of Polishing Plants




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