Worldwide, there is a disastrous situation in the field of wastewater collection and treatment: About 2.4 billion people have no access to adequate sanitation, 2.8 billion people use simple pit latrines and many countries, the conventional wastewater treatment works insufficiently. Many surface waters are polluted with raw wastewater and untreated faeces which present a big danger for the population. This situation contributes highly to the 5 Million people who die every year due to water borne diseases.
Additionally water scarcity increases more and more as well as soil degradation.
Also for the Eastern European countries, these issues are of crucial importance and alternatives are urgently required. For rural and peri urban areas, alternative, innovative solutions have been developed, applied and are available today (Ecological Sanitation).
The principles of these Ecological Sanitation (EcoSan) concepts are source control and hygienisation of the wastewaters followed by water and nutrient reuse in agriculture.
The mayor objective for sanitation is minimizing hygienic risks. New systems should be better than conventional sanitation systems which have a good hygienic standard for inside the houses but in most cases not for receiving waters. But also in terms of costs and benefits, the new systems must show advantages as the conventional sanitation and wastewater system (flush and discharge principle) requires high costs for investment, particularly for the sewerage, but also for operation, mainly the technical aeration, which cannot be covered by the citizens without high subsidies.
Thus, a closer look at the wastewater itself can help finding the right solution.
Wastewater from different sources has different distinctive characteristics. Thus, household wastewaters are described by colors: grey for little polluted water from kitchen, washing, etc., black for toilet wastewater, which can be divided further into brown (faeces) and yellow (urine) [Otterpohl 2001]. The most important parameters are shown in Table 1.
Table 1. Characteristics of the main components of household wastewater
Table 1 leads to the following conclusions (Tettenborn & Otterpohl 2004):
Most of the soluble nutrients (N, P, K) of domestic wastewater are contained in the comparably small volume flow of "yellow water". Separately collected urine, converted for agricultural usage, is the biggest step towards nutrient reuse, highly efficient water protection, and improved wastewater treatment. Moreover, urine contains trace metals required for plant growth. Thus, yellow water has to be taken into consideration as fertilizer. It is related to the nutrient cycle rather than to the water cycle.
The increasing focus on residual organic pollutants like pharmaceuticals, which are distributed by human wastewater in the surface waters, is supporting the installation of the source separation. With separation of the urine the widely spreading of these components in the natural environment can be avoided.
The hygienic danger of wastewater comes almost exclusively from pathogens contained in faecal matter. - Faeces suspended in the huge volume flow of greywater means spreading the pathogens in a large volume of water, making the reclamation for reuse more expensive. Separation and low or no dilution opens the way to excellent hygienisation. - "Brown water" contributes greatly to the phosphorus load of domestic wastewater and thus can also be considered as fertilizer. The organic solids make brown water an excellent soil conditioner after suitable treatment. Therefore, also brown water belongs to the nutrient cycle which should not be mixed with the water cycle.
Wastewater that is not mixed with human ’waste’ (faeces and urine) -so called "grey- water"- is the biggest volume part of all. Because of its low contribution to the mass flow of the nutrients, greywater represents a splendid source for high quality reuse. Greywater contains nearly half of the organic load of domestic wastewater. Removing these pollutants before eventual reuse of greywater is far less expensive than additional removal of nutrients, as it is realized in modern wastewater treatment plants. Bio-sandfilters and membrane technology open cost-efficient ways of production of secondary water - on-site, local, or regional scale can be appropriate.
Rainwater runoff is one of the reasons for building sewerage systems. Local infiltration or trenches to surface waters for relatively unpolluted rainwater is often feasible and can be combined with usage.
Any sanitation system aims to a hygienically sound situation as efficient as possible. In sustainable/ecological sanitation concepts this is achieved by separating the water cycle from the nutrient cycle, and closing both loops.
Two Examples of Sustainable/ecological sanitation
Many examples worldwide, as well in industrialized as in developing parts, prove not only the feasibility, but show how beneficial these concepts are [GTZ 2003]. Here are presented two EcoSan systems, one in Germany and one in Ukraine.
An advantageous low-cost and low maintenance system with a potential of full resources recovery for smaller villages and single houses is based on urine sorting flush toilets (no-mix-toilets). Yellow water is collected without dilution and is used after storage directly in agriculture. Brownwater is treated in a two-chamber separation unit (Rottebehaelter) where each chamber is used for half a year and left without further charge the other half. The produced compost can be used for improvement of long term soil fertility. The filtrate from the separation unit is low in nutrients due to the previous separation of urine. Therefore, the filtrate can be treated together with the greywater (except if high quality reuse of greywater is planned).
A pilot project of this system is operated in an ancient water-mill museum ’Lambertsmühle’ in Germany. In connection with the restoration of the building, this sanitation solution has been developed. The urine sorting toilets collect the urine undiluted (Roediger) or little diluted (Gustavsberg) (see Figure 1). The faeces are flushed with an appropriate volume of water (2 - 6 l per flush).
Figure 1. Urine sorting toilets, left German company Roediger,
Greywater from the kitchen, bathroom etc. is treated in a constructed wetland and then discharged to the receiving water.
A scheme of the sanitation concept regarding to the water and the nutrient cycle is shown in Figure 2.
Figure 2. Scheme of EsoSan concept Lambertsmühle [Otterpohl 2001a]
An sanitation system which is particularly reasonable in regions with no central water supply and no proper sanitation system is the application of dry urine diverting toilets.
The principle and use of these urine diverting toilets (or variations) has been established for many years in countries like Mexico, China and Vietnam. This kind of toilet consists of a toilet room with a seat riser or slab for urine diversion. For each toilet there are two (double vault) easily accessible faeces-chambers with a sealed floor made from concrete. The vaults are designed such that one vault is in use for minimum 1 year, then allowed to rest for one year while the other chamber is used. Ventilation pipes are installed from the faeces-chambers to above the roof to supply the vault with oxygen and avoid odour and flies.
The urine from the toilets and the waterless urinals is collected in two urine tanks and can be applied in agriculture.
In Stepanovka, Ukraine, it could be shown that the installation of double vault urine diverting toilets is a low cost, very fast, and easy to realise solution to protect the groundwater and to improve health conditions [Deegener & Wendland 2009].