Rainwater harvesting, water re-utilisation and ecological sanitation – further developments

Increasing anthropogenic environmental noxious, the change of soil exploitation and the climate change show a risk to the availability of water resources. Also the insufficient water resources in the single countries, various states of sophistication, social aspects and in many areas the low standard or a not even excisting water and public sewage systems in different parts of the world are responsible for the mean supply of water. Experiences have shown that the water supply as well as the sewage water systems and clearings can not be treaten separately. Even Germany with its high level of technology has to face many problems in this point. The costs of preservation of the physical structures and systems for turning water into drinking water to such a standard which is requested in the German rules are very high. Main reason therefore is the increasing contamination of groundwater and the resulting efforts for the cleaning of "rohwasser". The traditional water-carried waste disposal as a kind of transport medium for faeces- becomes 
a critical look in fact of the sustainability. Comparing to the European countries which discuss the sanitary risk already at the point of  using rainwater for toilet flushing and washing machine, most other countries will be content to dispose water in such a quality as the mentioned drinking water.

Based on these facts different technical innovations for a lasting water resource management and sewage systems have been developed. Main aspects were the responsible commerce of water, which means a lower consumption and decrease of water contamination as well as a consistent partical flow management.
Whilst Europe focus mainly on technologies for saving water and efficiency of water recycling in all processes - biological, chemical and physical – different parts of the world are still in work for water and public sewage systems in general.
The constitution of new systems also means to renew all kinds of inspections and the modification to the already existing administrative guidelines. In Germany there exist e.g. the "Anschluss- und Benutzungszwang" for properties to the public infrastructure. Therefore many different administrative proceedings will have to be settled for any kind of technical innovations of the water resources management for communities.
So far main points in Germany were to reduce the consumption of drinking water. Technical installations as water saver fittings were a success in the sanitary area. A further important part is the rainwater harvesting and water re-utilisation. Through the substitution of drinking water by rainwater or different systems of grey water recycling, drinking water can be saved in one single household up to 50 %.

Rainwater Harvesting – State of the Technology

Systems of rainwater harvesting were used all around the world with different technical efforts. Reservoirs and transport of water in mainly used in the agricultural area. The utilization of rainwater in the domestic area constantly increases. While in developing countries the rainwater in general is collected on a low-technical standard for domestic applications and on the regional level also as drinking water and for personal hygiene, in other countries the collection of rainwater, predominantly to the industrial countries, becomes a substitution of drinking water, which then will be used for various ranges of application as toilet flushing, washer and garden irrigation. The technology of the rainwater harvesting offers numerous products for different application cases and installation sizes. A wide range of products are manufactured and are offered in the mean time.
The following Illustration 1 shows a rainwater installation used in the domestiv area/household according to the state of the technology.

Illustration 1: Rainwater Harvesting System with Ground Reservoir 

This installation is essentially based on 2 modules. The illustration shows a central rainwater system in a domestic area, combining a pump, a supplemental feed module and the system control unit. It also shows reservoir modul, which integrates the reservoir, quiescent supply, removal line, overflow and filter completely.
The modular construction enables complete, industrially prefabricated arrangements parts finished with connection in different equipment variants and price ranges to produce. So far the possibility is given to combine different components which are to be started if necessary with alternative sanitary systems meaningfully. Numerous physical-chemical and hygienic examinations/tests prove that the quality of the rainwater from these kinds of installations is suitable according to the state of the technology to use the water for the toilet flushing, washing machine, the garden irrigation and for cleaning purposes.

Turning Rainwater into Drinking Water

With water treatment systems as e.g. of Aqua Sure, The Netherlands rainwater can be proceeded into drinking water quality. Through the storage of rainwater and subsequent proceeding, these systems offer possibilities to construct public drinking water systems to smaller communities and villages or at least at the domestic area. These systems are mainly designed for regions, which do not dispose of a drinking water infrastructure. The following pictures show a water treat system, which works with the usual process of drinking water recycling as pre-infiltration, adsorption, ion exchange and disinfection. The tool is build up on a modulare basis an works on a 40 l/h capacity. This is equal to satisfy the daily supply of a family.

Illustration 2: Rainwater Treatment Technology RainPC, Type AquaSure bv, The Netherlands 

Whilst countries with sufficient water resources the supply with drinking water does not show the main problem, regions with less water resources rainwater these becomes an important aspect referring to the daily water supply. By using the new developed, dezentral Wasseraufbereitungsgeräten rainwater can be turned into drinking water.
The use of rainwater in addition /as a supplement to process water, for cool systems and cleaning purposes and other applications in the commercial or industrial areas is already implemented in a lot of cases. Here, first of all, economic reasons were the clincher. Dependent on the fees for drinking water water and the connection on the public sewage water systems these investments amortize themselves in relatively short intervals.
The image shows a sample of an installation for the commercial area. 

Illustration 3: Rainwater Harvesting, an example for a commercial area

Grey water-reuse – State of the Technology

An increasingly more important role is ascribed to the grey water reuse by the development of a sustainable water resource management. Water recycling in the domestic area is not basically new, but the comfort claims and the lifetime habits concerning water and body hygiene have strongly changed compared to the past times. The water-consumption has risen in this area definitely.
Today water recycling means to grasp and to treat slightly loaded domestic sewage water (grey water) and sewage contaminated with faeces (black water) separatly. Typically grey water is such water as the drain of bathes and shower sewage, washing table and the washing machine. In a water-saving household in Europe approx. 50 to 55 l of grey water are consumpted per day and person.
In fact of the low nutrient content a simple biological cleaning will satisfy the expectations. Based on the daily personal hygiene grey water continuous comes up not depending on any kind of weather influences. The arisin grey water can be grabed to quality of process water, which gives the possibility to use this water for toilette flushing, washing machines as well as for watering demands. Grey water systems can be implemented decentralized as well as centralized. Decentralized grey water installations are, e.g. installations which process the grey water in the point of origin during central arrangements will bring the water from several housing units together and process them. The grey water use assumes a functioning drinking water supply system to use the water by cycle guidance repeatedly. The following image shows a grey water installation in a new built housing area with 120 units at Bejing, China.

Illustration 4: Grey water system with system control unit, Type (IRM®-MAX) in Beijing, China

Ecological Sanitation

The ecosan concepts is based on a consistent separation of partical flow. The recycling of nutrients taken from the sewage of domestic areas is most important. Analyses of partial flow show, that the nutrients are from the human excretions urine and faeces. For the further use of these nutrients special technologies are necessary to reduce and avoid the dilution of the partial flow. By the use of special sanitary systems as separation toilets, vakuum toilets and compost toilets the separation of the partial flow can be guaranteed. In an optimal case a complete recovery/retrieval of nutrients in the sewage water taken from the domestic area will happen. A further combination of systems for solids und also power generation under assistance of biogas reactors is also possible and have successful happened.

Furter-oriented combinations of rainwater harvesting, grey water utilization and ecosan technologies

Sytems of process water and rainwater harvesting and grey water recycling are already in use and proceeded in different countries. Similar systems are already in use for the ecosan technologies. It is recommendebal to avoid any kind of administrative restraints for the implementation and realisation of new and further oriented innovations in the denzentral 
solutions Actual there are multifaceted technologies, which can be accommodated to the individual financial situation of the particular country.
So far systems of rainwater and process water harvesting were successful used in main regions showing an existing drinking water infrastructure and public sewage system. Possibilities of combinations of the suggested systems have to be proven accordingly to the different contraints. For countries with lower rainfall the question of the quantity of collected and stored rainwater has to be clarified. It will also be important to get further information about the annual spread of rainfall, roof and collecting areas/fields as well as about the possibilities to collect and store this water.
It has to be taken care in general that countries which will investigate ground for further communities or villages, especially the developing world with a low budget of water resources, should not work with any kind of Schwemmkanalistaion. The combination of ecosan technologies and grey water recycling should be preferred. The grey 
water can be drained in a dezentral soil filter and be trickled down or can be drained into the Vorfluter.
It other regions with other constraints it has to be proven which kind of combination of the single systems will be the most effective. Additional it should be considered that the installations should only use as less energy as possible so this may guarantee that regions without any infrastructure can use this installtions dezentral by photovoltic or biogas installations.

It is also possible that in the sense of economical aspects and in view of an already excisting infrastructure, the combination with rainwater harvesting and grey water recyclingshoul be continued. For the development of the responsible treat with water in municipales in general, the elements of ecosan technologies as well as rainwater harvesting and water re-utilisation systems will become more and more important. The combination of both strategies will be a new task field referring to the planning, installation, operation and maintenance. Therefore further research projekts and modell test are required.

Dietmar Sperfeld