In nature everything operates in cycles. For wastewater treatment reuse and recycling becomes important issues when ecological thinking is applied.
Minimizing the reliance on fossile fuels is another criteria which may influence design and selection of system type. Ecological thinking also means to tailor the wastewater treatment system to local conditions beeing natural, economical, social, or religious.
This means that ecological sanitation is not fixed to any one system, but essentially considers all available sanitary systems. In order to design a sustainable system we need to have a holistic systems approach based on ecological thinking.
However, recycling may be facilitated if the wastewater is source separated into black- (toilet waste – urine and faeces) and greywater (water from showers, sinks, kitchen) becauce the majority of the resources (plant nutrients as nitrogen phosphorus and potassium and organic matter) in wastewater are present in our excreta. Hygienizing excreta opens interesting possibilities for cotreatment with other organic waste from households and/or agriculture and generation of bioenergy.
The simplest natural (ponds, wetlands, soil infiltration) systems can operate by gravity alone and may not need mechanical devices, hence, they are often favored because of low energy requirements. Ecological sanitation is therefore often associated with natural systems and systems that utilize source separation (i.e. urine divertion) in order to reclaim and recycle resources in wastewater as plant nutrients, organic matter and water. The main focus of wastewater research in UMB is connected to natural and source separating recycling systems.
Conventional sanitary systems (centralized collection system and a technically complex treatment processes) can produce a better ecological result by optimizing resource gains and minimizing resource use. Energy can be obtained from wastewater through the use of heat pumps and biogas generation from sludge. When optimized in this way, conventional systems are not necessarily ecologically inferior solutions.
It is unlikely that one single system can solve all future sewerage problems. Large investments have been made in conventional sewage systems which will be in operation for decades, but conventional systems will evolve as the principles of ecological thinking are communicated to the engineering society.
Totally new systems, as well as hybrid or combination systems, will appear. Schools that teach ecological engineering and consultants and companies that implement ecological engineering will have advantages in the market because they can offer a broader range of solutions and solutions that more easily fulfill local requirements, and a variety of systems are needed to meet the natural constraints of different regions, differing legislation, different sociological aspects, different budgets, health considerations and personal needs and preferences (read more).