The Utilization of Rainwater

The Utilization of Rainwater

When I think about how to economize water resource in order to provide more drinking water for the world people, neither the reuse of wastewater nor the desalination of sea water is cheap enough. However, the utilization of purified rainwater might be afforded by the public. This supposition is verified by the accessible information. It's said that the cost of purification systems of rainwater is only a third of the cost of desalination of seawater, and the infiltration trenches can save as much as 10%-20% of the cost of stormwater disposal. Besides the lower cost, precipitation in some countries, which are most in need of drinking water, such as Singapore, is very plentiful. Set China as an example, which has a mediate precipitation, rainfall in every 22 square meters is enough for 200,000 people to use.

Utility Designs

As the rainwater is relatively pure, it can be saved and purified by the gardens or pools on the top of high buildings. The pool should be an ecosystem made up with soil, vegetations and other component if necessary. It can keep the water fresh and pure. When the rain is pouring, we can open the brake of the drainage to let the water go down to the road. After some disposal of filtration and disinfection, the water in pools can be drank directly.

Secondly, the rainwater could replenish the underground water through infiltration disposal. It is required that the road be paved with both bricks with grass and gravel with holes, and more grass should be planted. Besides, we could pave more infiltration trenches and improve the infiltration capability of the earth. In these ways, rainwater will help solve the underground water crisis caused by overuse. The feasibility of this design lies in the cheap, effective and efficient infiltration disposal.

To carry out the infiltration design, it's necessary to ensure that the rainwater does not pollute the underground water. The harmful substances in the rainwater are mainly heavy metals, microbes, ammonia, nitrogen, cations and anions. But according to some researches, a infiltration of rainwater will not cause pollution. Because the heavy metals cannot penetrate deep in the earth. Some 99% of the heavy metals will be kept in the surface, and thus be broken down there by the effect of adsorption, ion exchanging, etc. The microbes cannot either, only 0.07% of which exist 3 meters below. The cations and anions are dissolved in the earth and are absorbed by plants with their roots. The concentration of the ammonia and the nitrogen reduce to 30mg/L when reaching the underground water. The other factors such as COD and TSS are also purified by the earth. In a word, the rainwater could be used to replenish the underground water. However, the rainwater near hospitals shouldn't replenish the underground water, and the underground water near headwater should not be replenished for security reason either.

Thirdly, with the increasingly more constructions of wastewater reuse centers', and the more developed technology in this aspect, rainwater can be caught to supply the wastewater in more countries.

In addition, we could utilize the rainwater directly, though more expensive. It requires building rainwater catchments on the roof, under ground, and building more multi-storage buildings. After the collected rainwater is processed in certain physical, chemical and biological ways, it could be used directly, like washing toilet. But this method is actually not very good, for the channel construction is costly and some negative change will be brought about to the structure of buildings.

Suggestions on Extensive Use of Rainwater

In order to make better use of rainwater, we suggest that roads be built with infiltrated bricks and gravel, more grassland and raised flower beds be developed so that rainwater could get down and replenish the underground water more easily. Secondly, we could use environment friendly materials for the roof, and keep the road clean so that the rainwater quality will be improved. Thirdly, the utility systems could be operated in the new constructed communities, villas, hotels and schools first, where the technical basis is good. Besides, we could cooperate with developed countries, from which we learn the utility techniques. Last but not least, we could treat the rainwater differently. For example, the first flush is dirtier than the latter flush, and the rainwater on the roof is generally clearer than the water on the ground, so they can be saved in different tanks, processed in different manners and finally be used in different ways.

At last, I believe that by utilizing rainwater, we will provide more people in the world with drinking water. To see their smiles, who suffered from thirst and diseases, is forever my supreme pleasure!