 |
Simulation Studies · New Sanitation Strategies · Integrated Technology for Residential Areas |
Sustainable Sanitation Systems
Introduction
Technical principals
Options for developing countries
Practical Solutions
|
Simulation Studies · New Sanitation Strategies · Integrated Technology for Residential Areas |
Sustainable Sanitation Systems
Introduction
Technical principals
Options for developing countries
Practical Solutions
The problem of conventional sewerage systems is the mixing of the food and water cycles. Central sewerage systems not only consume high amounts of freshwater but also dilute nutrients (phosphorus, nitrogen) and organic substances to such an extent that only a small part can be reclaimed for agricultural use.
The nutrients are washed away with the purified wastewater and are emitted to rivers and the sea where they are extremely harmful (eutrophication). In turns, more nutrients have to be produced for agriculture, causing depletion of fossil resources and high energy demand.
The purpose of sustainable sanitation systems is the closing of the water and nutrients cycles, taking into account that the main task of sanitation is to assure highest hygienic standards in a cost- effective, environmental sustainable way, saving both water and energy and keeping soils fertile.
This can be achieved by separating different qualities of waste from human settlements: Blackwater (toilet wastewater), greywater (washing, cleaning), stormwater runoff, biodegradable and non- biodegradable waste.
Such sanitation reduces the freshwater consumption considerably and produces fertilizer for agriculture instead of waste. Maximum recycling of nutrients is the basis of sustainable food production and sanitation systems.
Conventional Sanitation System
· End of pipe technologies - linear throughput economy
· High input of matter (resources) and energy for fertilizer production
· High loss of nutrients (phosphorus and nitrogen) due to solution and washing
out (only about 30 % can be recovered from excess sewage sludge)
· Accumulation of nutrients in surface waters cause eutrophication
· High water consumption due to central sewerage systems
· High costs and energy demand for construction, operation and maintenance of
central sewerage systems
· High energy demand for the degradation of organic wastewater contents
(carbon)
· High amount of non recyclable waste and therefore high demand for expensive
treatment facilities (incineration plants and landfills)
Sustainable Sanitation Systems - Technical Principals
Centralized sewerage systems, water flush toilets and aerobic wastewater treatment plants should not be considered as the only possible solution for sanitation. Advanced systems with source control can avoid many problems of the conventional end-of-pipe technology by respecting different qualities of wastewater and waste and by treating them for reuse.
Classification of Domestic Waste and Wastewater for Sanitation
|
Waste Stream |
Treatment |
Related Cycle |
|
Kitchen waste and blackwater of low-diluted feaces (high nutrient content) |
anaerobic digestion or composting |
food cycle |
|
Brownwater, blackwater without urine or yellowwater |
anaerobic digestion or composting |
food cycle |
|
Yellowwater, urine from no-mix-toilets and urinals (with or without water for flushing) |
long-term storage, drying, treatment with acid |
food cycle |
|
Greywater from bathrooms, washing and kitchen (low nutrient content) |
aerobic treatment by biofilm technology or plants |
water cycle |
|
Stormwater run-off (very low nutrient content) |
local discharge or infiltration |
water cycle |
|
Non-biodegradable solid waste (small fraction with reuse of packages) |
processing to raw material |
material cycle |
· Kitchen waste and blackwater (group 1) contain nearly all
of the nitrogen and phosphorus nutrients. In blackwater, the majority of
nutrients is concentrated in urine thus making separate treatment feasible.
· Greywater (group 2) contains few nutrients as long as phosphorous free
detergents are used. It can easily be treated to a reusable quality as it had no
contact with toilet wastewater. Biofilm systems like trickling filters, rotating
disk or sand filters (technical or as constructed wetland) can recycle nutrients
released by of biomass.
· Stormwater (group 3) infiltration has become increasingly popular in many
countries in recent years. The advantages - the recharging of groundwater,
maintenance of the local water cycle, smaller sewerage system and cost reduction
- are obvious.
· If collected separately non-biodegradable solid waste (group 4) can be
reduced and easily recycled.
Sanitation systems, based on this classification and on source control can be designed in many variations to meet local demand and technologies. Their principles are easy to understand and their performance meets highest standards of hygiene and economy.
Sustainable Sanitation System
· Closing and separating the cycles of water and nutrients;
avoidance of hygienic problems due to the separation of faeces from the water
cycle
· Reclamation of nutrients (phosphorus and nitrogen) for agricultural use and
hence saving of resources and energy (for the production of artificial
fertilizer)
· Considerable savings of freshwater through the use of water saving toilet
systems (vacuum, separating or dry toilets)
· Energy production (biogas) instead of energy consumption (for carbon
degradation in sewage plants)
· Savings of construction, operation and maintenance costs compared to the
conventional central sewerage systems
· Sophisticated modular system, which can be adapted perfectly to local social,
economical and environmental conditions
· Easier operation and maintenance compared to centralized technology; local
job creation
Options for developing countries
Conventional central sewerage systems are not only questioned in industrialized countries but even more so in many developing countries due to their economic, environmental and health situations. Shortages of clean drinking water and health hazards arising from inadequate or absent sanitation facilities, demand alternative solutions.
Sustainable sanitation systems are most appropriate for human settlements where no sanitation systems exist, in particular rural settlements and low income quarters of big cities, as well as refugee camps in disaster areas, where hygienic problems due to water pollution from faeces can undermine relief operations.
All components needed for a sustainable sanitation system (appropriate toilets and latrine components, biogas plants and greywater treatment facilities) are readily available and have been tested in practice.
An optimized system can be planned for any community, taking into account local conditions, the climate, the agricultural and environmental situation, technical requirements and available financial resources.
The modular components can be selected and combined from a wide range of solutions ranging from high-tech solutions (as described for the German pilot project) to low-tech-low-cost solutions (as desiccation latrines and biogas plants which do not have to be heated in warm climates).
The wide range of existing technical solutions makes this concept adaptable to various local conditions, ranging from sanitation concepts for urban and rural areas to disaster relief measures and the rebuilding of infrastructure after natural disasters and wars.
Two examples show the practical implementation of sustainable sanitation concepts:
Ecological settlement Lübeck- Flintenbreite
An integrated sanitation concept with vacuum toilets, vacuum sewers and a biogas plant for blackwater as well as greywater treatment in reed-bed filters; under construction since 1999
Pilot project "Lambertsmühle zu Burscheid"
Sanitation concept with urine separating toilets and waterless urinals, brownwater treatment in a rotting chamber/compost separator, greywater treatment in reed-bed filters
For more information please see
List of references
or List of
publications