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Table 0.2 Survey of potential secondary plants in the municipality of Herlev and their need for

process water.

Secondary plants Need for process water

m 3 /year

Process

Iron and steel manufacturer 4.400

Cooling water

Water for phosphatizing process

Steel heat treatment 7.000 Cooling water

Lock factory

5.000 – 7.300

Water for chromium-plating process

PVC manufacturing enterprise 4.200 Water for cleaning of process air

Service station 2.500 Car washing

Municipal store house 600 Cleaning of vehicles

The identification of highly water consuming enterprises has indicated that a number of

industries would be willing to accept a reduced quality of the supplied recycled water compared

to the normal drinking water quality. These enterprises are listed in Table 0.2.

Based on a distance and water volume matrix a number of possible couplings between the

selected potential primary and secondary plants were evaluated in order to find the optimum

conditions in relation to exchange of heat volume and geographic proximity. The two

most obvious scenarios were:

Scenario 1: The Central Pharmacy (P) – Northor A/S (S)

Scenario 2: The swimming bath “Hjortespringbadet” (P) – Papyro-tex A/S (S)

In scenario 1 the need for upgrading of the water quality is insignificant, as the quality of

the water exchanged in this case is close to that of drinking water. The water, which consists

of surplus distillation water and a dilute concentrate from an Reverse Osmosis plant is

supposed to be slightly aggressive but this can be remedied by means of a pH adjustment

and by adding calcium oxide, if necessary. The water is primarily meant to be used in

cooling water and phosphatizing processes at Northor, which is an iron and steel manufacturing

enterprise situated approx. 100 m from the Central Pharmacy. It should potentially be

possible to exchange approx. 4.400 m 3 /year if an equalizing tank at a size of 10 m 3 is established

near the Central Pharmacy in order to counterbalance the flow variations. Since the

water quality is high, no crucial working occupational health problems need to be taken into

consideration. Based on a logistic review of indoor and outdoor conditions at the enterprises

in question in relation to the establishment of a complete grey water exchange system,

the economic situation was analysed. Thus, the total construction investment was

calculated to 509.575 DKK not counting the yearly expenses of 15.690 DKK for maintenance

and operation of the system. The water savings correspond to 89.900 DKK/year

based on a water price of 20,43 DKK (exclusive of VAT and water charge), resulting in a

net present value of the investment of 52.600 DKK/year during a depreciation period of 20

years with a real interest rate of 4%.

Scenario 2 deals with exchange of shower water collected from the bathrooms of the

swimming bath “Hjortespringbadet”. The water is transported to the company Papyro-tex,

which is a hot-pressing enterprise (manufacturing PVC foil) using water for cleaning of

process air. The distance between the two enterprises is approx. 250 m. It was required by

Papyro-tex that no particles, which might cause a blocking of the sprinkler jets, were allowed

in the grey water. Furthermore, it was important to ensure that no odour nuisances

could arise during recycling of the water. The swimming bath uses approx. 5.500 m 3 /year

of water for showering and approx. 1.200 m 3 /year for filter rinse while Papyro-tex for the

time being only needs approx. 3.500 m 3 /year, which can be covered by grey water from the

“Hjortespringbadet”. In order to equalize the difference in flow variations it will be necessary

to establish an equalizing tank of 15 m 3 .

For treatment of the grey water a combination of a pressure sand filter and a UV-system

was suggested to remove particles and inhibit the microbial growth in the equalizing tank.

In addition, a cartridge filter should be installed at the drainage for further removal of part icles

in the water flow. Thus the treatment system was not designed for a complete treatment

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