FIELD OF INVENTION
The invention relates to a method for recycling of cooling tower blow-down water by
using the recycled water as make-up for cooling tower. More particularly, the invention
relates to a method for recycling of blow-down water back to the cooling tower as
make-up water after being treated in a Cooling Tower Blowdown Recycling Plant
comprising of Pre-treatment plant and Reverse Osmosis plant.
BACKGROUND OF THE INVENTION
The heat dissipation in Cooling Tower is based on the principle of evaporation which
leaves behind dissolved solids in the system. In a Closed Circuit Cooling Water System,
the same water being circulated again and again the dissolved solids get accumulated
in the system. To avoid fouling of condenser and other heat exchanger tubes due to the
built up of dissolved solids in the system, some quantity of circulating water (which is
called as C T blow-down) is taken out from the system and replaced with less tower
dissolved solid (TDS) water known as cooling tower make-up water which makes up for
the water lost from the system due to evaporation, blow-down and drift loss. This
Cooling Tower blow-down is normally disposed off to the plant drain system as the
water cannot be used due to the high concentration of salts and suspended solids after
recirculation of the cooling water. Hence, there is a huge loss of water through

drainage. It is therefore, a necessity exists to find a process to combat with the loss to
reduce plant water consumption. This high tower salt and suspended solid water (TSS)
and high TDS water can be treated in a Cooling Tower Blowdown Recycling Plant
comprising of Pre-treatment plant and Reverse Osmosis plant and can be reused as a
make-up to cooling tower.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose a method for recycling of cooling
tower blow-down water which eliminates the disadvantages of prior art.
Another object of the invention is to propose a method for recycling of cooling tower
blow-down water which is capable of reducing plant water consumption.
A still another object of the invention is to propose a method for recycling of cooling
tower blow-down water which is capable of reusing the blow-down water as make-up
water
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
Fig.l - It shows the method for recirculating the cooling water using pre-treated
cooling tower blow-down water as make-up water

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
As shown in fig.l, a cooling tower (D) is equipped with cooling water pumps (E) for
discharging the cooled water to heat exchangers (HE) through main delivery line F. The
cooling tower blow-down water (A) is being drawn in from cooling water pump
discharge header for treatment in pre-treatment plant (B). After being treated in plant
B, the CT blow-down enters reverse osmosis plant C while the sludge from plant B is
disposed of. From plant C, the rejected water goes to drain while treated CT blow-down
water goes back to the cooling tower (D). The cooling water pumps (E) delivers the
cooling tower water to cool the heat exchangers (HE). The cooling tower is used to cool
the cooling media (normally water) which in turn is used to cool the process fluids,
utilities etc. in the heat exchangers and coolers in the industries. The cooling water is
cooled through ambient air in the cooling tower. This cooling water is circulated to the
various heat exchangers, coolers etc. through the cooling tower.
Cooling towers (D) are being used in almost all types of industries to cater to the
cooling needs of various equipment in the power plant. In order to cool the process
fluid heat exchangers (HE) water is used as a cooling medium. This cooling medium i.e.
water is in-turn cooled in the cooling towers (D). The cooling tower (D) works on the
principle of evaporation cooling where the cooling medium i.e. water is cooled with the

help of ambient air. The cooling water is sprayed from the top of cooling tower
through fills in order to increase the surface area and contact time for better cooling.
This
cooled water is circulated to the various heat exchangers (HE) by means of circulating
water pumps. In the process of evaporation and drift loss the concentration of
suspended solids, salts etc. increases in the recirculating cooling water. In order to keep
the level of salts, suspended solids etc. in the recommended limits, a certain amount of
water is blown down. This loss of water (evaporation and drift loss and blow-down loss)
is made-up continuously with fresh water in the cooling tower (D). Normally the cooling
tower blow-down is routed to plant drain as it is contaminated with salts.
The invention is focused on the reuse/recycling of this blow-down water back in the
cooling tower as make-up water, after treatment in a Cooling Tower Blowdown
Recycling Plant comprising of Pre-treatment plant (B) followed by reverse osmosis (RO)
plant (C).

WE CLAIM
1. A method for recycling of cooling tower blow-down water comprising the steps
of:
discharging cooled water to heat exchangers (HE) by the cooled water
pumps (E) through main delivery line (F);
drawing of CT blow-down water form cooling water pump discharge header
from main delivery line (F);
passing the CT blow-down water to a Pre-treatment plant (B);
disposing the sludge from plant (B);
passing the pre-treated CT blow-down water into a reverse osmosis plant (C);
draining the reject from plant (C);
delivering the pre-treated salt and sludge free CT blow-down water into
make-up water line (G);
delivering the make-up water to the cooling tower (D); characterised in that
the loss of water is made-up continuously with fresh water in the cooling
tower (D).
2. A method for recycling of cooling tower blow-down water, as claimed in claim 1,
wherein the treatment is done in Cooling Tower Blowdown Recycling Plant
comprising of pre-treatment plant (B) followed by reverse osmosis plant (C).

A method for recycling of cooling tower blow-down water as make-up water for cooling
tower (D) to reduce plant water consumption consists of discharging the cooled water
to heat exchangers (HE) through main delivery line (F) while CT blow-down water is
drawn from the main line (F) to pass it through pre-treated plant (B) and reverse
osmosis plant (C) and delivering it to make-up water line (G) to deliver fresh water to
cooling tower (D). The slug is disposed of from plant (B) and reject from plant (C) is
drained out. The loss of water is made up continuously with fresh water in the cooling
tower.