Stormwater

Rain water is water from precipitation in liquid form, the rain. Rainwater as a product of the rain, constituting an essential element of the hydrological cycle of the earth

Storm water runoff

The infiltration rate of water (and other liquids in snow during defrosting ) into the considered substrate is designated by the infiltration rate and measured. Their size depends on the existing saturation of each soil and its chemical, physical, biological and mechanical characteristics. Here, in agriculture, the method of tillage and the respective planting considerable influence on the porosity of the substrate ( bottom culture). The machining with large and therefore heavy machinery promotes soil compaction. The colonization by living organisms plays a certain role: Numerous occurring earthworms loosen the topsoil to a considerable extent on. In vineyards, the system of transverse grooves promotes the retention capacity of more or less inclined layers. ( Heavy rain ) surface runoff will occur, the lower is the capacity of a soil, the faster with stronger rainfall.

Not versickertes water collects in depressions. Running this on, the water flows above ground next deeper point. Depending on the temperature, solar radiation, wind speed evaporates some of the water.

When fastened or sealed surfaces, the proportion of seepage is small (possibly evaporates at low rainfall the moisture). Most of the water flows more or less completely from above ground. In the drainage of roads outside of towns, rainwater is often passed over the shoulder directly sideways into a ditch or a depression in. If the conditions of the terrain or the contamination of the rainwater will not let the water through gutters and gullies is directed into a storm sewer.

The so-called separation system the rainwater gutters and gullies is directed into a storm sewer, while the dirty water of which is derived separately in dirty water channels within towns. In highly polluted areas, the rain or surface water due to the high pollution levels ( high-traffic streets - DTV - value ) is removed contrary to the normal derivative in a sewer.

The so-called mixed system, rainwater is also collected via gutters and gullies, but together with the dirty water ( mixed ) in a combined sewer derived. Since the peak discharge can not be treated in the treatment plant during heavy rains, combined sewer overflows are at suitable locations built on which forwarded mixed water on the order of two or three times the wastewater flow to the treatment plant and the remaining diluted water is released into a water body. Most of these relief is combined with a stormwater treatment.

For individuals, there are special rainwater collector, which can absorb at least 60 % of the rainwater. Such a device can be incorporated into standard zinc drainpipes around 100 millimeters in diameter.

Flood

Due to the increasing surface sealing occurs in heavy rains repeatedly overloading the sewage systems and flooding, as the water runs down motion immediately and can not seep into the ground. In the sewers or drains and surface waters from stormwater retention facilities be built to achieve a more uniform discharge to receiving waters and an attenuation of peak flows.

Pollution from stormwater

Rain water in the atmospheric and the drain on paved surfaces and in the storm sewer or combined sewer pollutants of various origins:

• Atmospheric pollutants and harmful substances (such as dust, water-soluble salts and acids see acid rain, radioactive fallout)
• Recorded at the surface materials
• From the housetops detached substances (eg, copper salts or asbestos fibers)
• Wastewater constituents of the dry weather runoff
• Resuspended materials from channel deposits
• Eroded Sielhaut

In combined sewer systems occur rather higher concentrations of particulate suspended matter, organic ingredients as well as nitrogen and phosphorus compounds than in separate sewer systems. There occur in some high concentrations of suspended solids, which may exceed the values ​​of combined sewer systems significantly.

The concentrations are very different depending on the catchment area, rainfall duration, rainfall and other factors. In the order, however, the contamination of rainwater from the rainwater sewers and unloaded mixed water are equal.

Stormwater treatment

For a minimization of environmental damage to water, is introduced into the rainwater, measures its purification ( stormwater treatment ) must be provided and constructed in rainwater sewer sedimentation tanks. In combined sewer overflow basins are established.

Use of rainwater

The use of rainwater as process water to conserve drinking water, enjoying increasing popularity. Rainwater is derived from this collection surfaces, for example on rainwater collectors, rainwater filter, etc. and collected in underground or above ground rainwater storage tanks, such as cisterns or rain barrels. Over-pumping the rainwater is transported from there to the individual taps. A four -person household can save about 70,000 liters of drinking water, for example, per year through the use of rain water. The actual amount depends on the location ( rainfall ) and the size of the usable roof area. In Germany rainwater can be used for flushing toilets, washing machine and garden irrigation. Even in industry and commerce, there are numerous uses.

However, the economy should be checked prior to purchase of a rainwater cistern, as a cistern in respect of fresh water, although ostensibly can save money, but the investment must be offset economically. It should be noted that, if necessary, fees for the wastewater to be paid and may be a fee for the installation of separate lines for the gray water.

More and more cities now go on to regard the waste water from rainwater harvesting systems as " positively influenced waste water" that would have been one way or introduced into the channel. Since in such cases for the rainwater often no sewage fee is payable, a reasonable sized rainwater harvesting system can in the course of her long operation ( cistern virtually unlimited filters / tubes 50 years and more, pumping more than 20 years) were expected certainly. This is especially true if there are grants by the municipality and the cistern is equal considered when building a house. In many places, this is now also part of the building regulations. In addition, for years the prices for fresh and waste water increases markedly in some municipalities. Rainwater use in the commercial sector is almost always economical because of the rain yield is determined by the size of roof areas and usually is given a large, constant water demand.

The ever given prompt dissemination of rainwater cisterns can reduce the risk of flooding in some sealed, channelized areas, because of the sudden, extreme increase can be sufficiently delayed with brief heavy rain or even completely retained (eg almost empty tanks after prolonged dry periods). The risk of flooding by this typical flows can be reduced in continuous rain, of course, hardly.

The use of rain water in rainy areas like the DACH countries has no advantages for remote arid areas, as the water balance in these countries does not change because of that. The use of rainwater is nevertheless classified as an environmental protection measure, as reduced in the immediate vicinity of the water use and groundwater extraction. Many large cities draw their very high water demand some from distant mountains (Frankfurt / M, for example, from over 50 km away Vogelsberg ).

Shipwrecked, the collection and use of rainwater as drinking water survival permit (see the corresponding self-experiments of Alain Bombard and Hannes Lindemann ).

Watering plants rain water is due to its low lime content ( low water hardness ) is more advantageous than, for example tap water.

Waste water fee

From impervious surfaces (roofs, parking lots, roads ) into the public sewer run-off and abgeführtes rain or surface water is not yet generally recognized as waste water ( only as a supplement to the fee for the dirty water ). His transfer was co-financed through the collected municipal wastewater charges. These in turn were calculated according to the freshwater consumption (probability scale). Only if a split wastewater fee for water and wastewater is collected, the sealed area is considered as a benchmark.

Meanwhile, multiply the nationwide assessments of the necessary calculation of the water and wastewater charges after a "split " fee.

A wastewater fee rainwater must turn only be paid if the impervious areas are actually connected to the public sewer. In the provinces, there are different ways to keep the rain water on the property. In some cases, the entire rainwater is recovered or seeps on the property. Then no stormwater fee must be paid.