WO1995014826A1

WO1995014826A1 - Method of achieving the uniform quality of water

Info

Publication number: WO1995014826A1
Application number: PCT/FI1994/000527
Authority: WO
Inventors: Kari Saarikoski
Original assignee: Aquasoil Oy
Priority date: 1993-11-24
Filing date: 1994-11-24
Publication date: 1995-06-01
Also published as: EP0731864A1; FI94654B; FI942527A0; FI94654C

Abstract

The objective of the invention is a method of achieving the uniform quality of water, in which water is fed to the network, having several water consumption points, network nodes (2-9, 11-21, 23 and 24), with a water pipe (34) in between, through which the water is fed from the feed pipe (21) to the water consumption points. The invention is characterized in that the water is circulated in the network independent of the consumption, by e.g. a pump (33) placed in the network, in order to achieve the uniform quality of the water.

Description

METHOD OF ACHIEVING THE UNIFORM QUALITY OF WATER

The objective of the invention is a method of achieving the uniform quality of water, favorably drinking water, in a water distribution system.

The water distribution network is often built and dimen¬ sioned bigger than consumer demands, due to e.g. fire safety regulations. The pipework is also dimensioned according to maximum demand. These factors, together with low consump¬ tion, cause standing of the water in the pipes. When the consumption is at minimum, the water flows slowly in the pipes, which means that there is no flow at all in several pipes.

When the consumption is low, the water does not move every¬ where in the pipes, causing that the water is no longer of uniform quality all over the network. In such cases is generally referred to the age of the water, which means how long the water stays in the pipes before consumed. When the water is old, the chlorine added in the water purification plant might have been used up, and the water is no longer hygienically acceptable. The low flow of the water can moreover cause increased scaling on the pipe walls. This leads to blockage of the pipes due to e.g. lime or rust formations, or causes corrosion on the pipe surface or enhanced microbiological activity.

The strict quality specifications for water put the water- works and the water distributors in awkward positions if the water quality is not within these limits. The use of addi¬ tional disinfectants increases the costs of chemicals. Substantial use of chemicals can cause side-effects, i.a. health risks. One way of affecting the water quality is to flush the water out of the pipework when the consumption is low, thus wasting valuable water.

A considerable improvement of the above mentioned disadvan- tages is achieved with the solution according to the inven¬ tion. The invention is characterized in what is presented in Claims.

The benefits of the invention are i.a. improved uniform quality of the water, and that the age distribution of the water stays favorably equivalent throughout the distribution network. The quality differences of the water between dif¬ ferent consumption points become even. The water flow pre- vents the deterioration of the water. No scaling is formed in the pipes causing corrosion and blocking of the pipes. The dosage of additional disinfectants can be considerably reduced because the quality differences of the water are minimized. Water is saved, as no flushing outside the pipe- work is required to secure the water quality.

The method according to the invention is described with reference to the enclosed drawing, in which:

Fig. 1 presents a model example of an distribution net¬ work area with no circulation pumping.

Fig. 2 presents a model example of a distribution network area using a circulation pumping according to the invention.

Fig. 3 presents a drawing illustrating the water flow as three-dimensional with the values of table 3, when no circulation pumping has been used.

Fig. 4 presents a drawing illustrating the water flow as three-dimensional with the values of table 2, when circulation pumping according to the invention has been used.

The invention is illustrated by a model example of a distri¬ bution network. Fig. 1 presents a water distribution network of a small-house area, comprising the nodes 2-9, 11-21, 23 and 24 and the pipes 34 connecting these nodes. The total consumption of the area is in the example 2,17 1/s, which quantity thus flows via the node 21. The water inflow to the area takes places via the node 21, in which the age of the water has been assumed to be zero. The table 1 of the model presents a calculation of the flow times in different con¬ sumption points without circulation pumping. Table 1 pre¬ sents moreover the water flow times in different consumption points with the circulation pumping according to the inven- tion. The circulation pumping is provided in node 23, in which has been installed the pump 33, from which the water is pumped along the line 23-24-17-18-19-20. The pipe lines 16-17 and 15-19 have in the calculation example been closed by the closing valves 31 and 32. It can be observed that the age of the water becomes substantially even in the consump¬ tion points due to the circulation pumping. The circulation pump is favorably placed in a spot where the age of the water would be highest without circulation pumping. To cause the water to flow in the whole network area, a closing valve or a valve capable of regulating the flow, has to be placed in certain points of the pipework, in order to achieve the desired water circulation. The existing pipework or part of that serves in the example as the return line 34A, wherefore additional pipe building is not required. The piles close to the return line 34A show the water flow direction.

In the example above, the network nodes have been assumed to be the consumption points. In reality the pipes to the consumption points start from any place along the pipe 34 or from the node. The node itself can be a consumption point. These pipes have possibly different branches, having at their ends or along themselves a consumption point or points. From these consumption points there is generally no return line to the distribution network.

The water flow in the network can be made more effective by a regulation valve, favorably valves controlled by the water flow. Thus, by controlling the water flow in the different branches of the pipework, the age variations of the water can be levelled, resulting in an uniform water quality.

The table 2 presents the water pipes, the begin and end nodes of the pipe lines, the length and dimension of the pipe as well as the flow velocities vl, illustrating the flow velocity without circulation pumping, v2, illustrating the flow velocity during the circulation pumping. The - sign indicates that the flow direction is opposite between nodes. According to the calculation example, the flow velocities v2 have in almost all pipe lines increased substantially, and especially in the lines lacking flow, the velocity has increased substantially. The uniform water quality is achieved in a closed circuit without flushing the water out of the water network.

Figs. 3 and 4 illustrate the velocity changes without circu¬ lation pumping and with circulation pumping. The flow veloc¬ ities of the network water have increased substantially, resulting in lower ages of the water in the different branches of the pipework than without circulation pumping. The invention requires the forming of a return line. The return line has to be build in connection with tree shape networks.

Cold water can be circulated between household consumption points inside the house, if a return pipe is formed. At least two service pipes are provided for the water circu¬ lation between the distribution network and the house.

The above described network can be connected and usually is connected to the other network or networks, e.g. through the node 21, said networks also having separate circulation systems by means of a pump or pumps within the network.

The networks function under pressure which usually varies according to the ground level. The pressure e.g. in the Nordic countries is normally c. 3 to 5 bar. In the invention the circulating of the water is achieved by conducting the water by means of the flow achieving means at least partly to the direction which is opposite to the original flow direction without circulation. The water or at least a part thereof, which is forced to circulate through the outlet of the pump, usually flows back via return pipe or other pipes, if not consumed during the circulation, back to the inlet of the pump. Thus, it is formed a ring or circle like loop into the network.

Table 1

N

Claims

1. A method of improving the uniform quality of drinking water, in which water is fed to the network, having several water consumption points, network nodes (2-9, 11-21, 23 and 24), with a water pipe (34) in between, through which the water is fed from the feed pipe to the water consumption points, characterized in that the water is forced to circulate in the network by a flow generating means (33) which secures the uniform quality of the water in the net¬ work.

2. A method according to claim 1, characterized in that the water is circulated by at least one pump (33), favorably placed in a spot where the water flow is known to be lowest.

3. A method according to claim 2, characterized in that at least some branch close to the pump (33) is closed by a valve, favorably a closing valve (31, 32) in order to con- trol the water flow.

4. A method according to claim 3, characterized in that the valve (31, 32) is controllable.

5. A method according to claim 1, characterized in that the water flow is controlled by at least one valve placed in the network, which is controlled by the water flow.

6. A method according to any of the claims above, characterized in that the water is circulated by at least one pump (33) and the flow is controlled by at least one valve (31, 32).

7. A method according to any of the claims above, characterized in that the water is circulated by at least one pump (33), and the flow is controlled by at least one valve, which favorably is controlled by the flow, and/or by the valve (31, 32) .

8. A method according to any of the claims above, charac¬ terized in that the water is circulated independent of the consumptio .

9. A method according to any of the claims above, characterized in that the cold water is circulated between the household consumption points inside the house.

10. A method according claim 9, characterized in that for the circulation of the water between the distribution net¬ work and the house there are provided at least two service pipes.

11. A method of achieving the uniform quality of drinking water in the water network, which comprises pipes in which the water is under pressure, nodes in the predetermined places of the pipes, at least one point through which the water is fed to the network, consumption points which are connected through said nodes or separate connections to the network acting as outlets of the network, characterized in that said method comprising the step of forcing the water to circulate in the water network by a flow generating means (33) provided in the network to secure the uniform quality of the water.

12. A method according to claim 11, characterized in that circulating water or at least a part thereof, which is forced to circulate through the outlet of the pump, usually via return pipe or other pipe, if not consumed during the circulation, back to the inlet of the pump.

13. A method according to claim 12, characterized in that circulating the water or a part thereof through a ring or circle like loop formed into the network.