SANSED PROJECT
1
General Scope
Substrates from decentralised water
management may supply nutrients to agroecosystems. But to apply these substrates
they have to be hygienically safe and match site specific demands depending on
soil and plant production. A new interdisciplinary approach is described how
water management may be linked with agriculture.
The general aim of the project is
the use of substrates from rural (decentralised) waste water treatment in
agriculture in an economical and ecological
sensible
way and to implement decentralised waste water treatment as an essential part of
rural water management systems. The experimental region will be the Mekong
Delta.
In a first step the ecological
demands of characteristic and representative agroecosystems in the Mekong Delta
will be analysed. Based on
these information suitable
fertilisers for the agricultural production are defined, i.e. fast/slow release
fertilizer, consistence (e.g. liquid, sludge, solid). Depending from the kind of
fertilizer identified, decentralised WWTS are recommended. Besides the analysis
of nutrient fluxes and agroecological studies this systemtic approach includes
also hygienical and socio-economic project groups. In
Part 1 of the project this approach
will result in a Handbook that can be used as a basis for future planning of
waste water and drinking
water facilities.
In Part 2 of the project, systems
for water management will be implemented and tested.
These technologies should help to
perform sustainable food production in terms of nutrient cycling, hygienic
considerations and pollution.
The proposal is based on the
announcement of the BMBF „Dezentrale Wasserver- und Entsorgungssysteme“
(Decentralised systems for drinking water supply and waste water treatment)
The project wants to develop a
general applicable decision tool for engineers to design an appropriate
decentralised WWTS, that
(i)
Treat the
WW reliably in terms of hygienic aspects
(ii)
provide
adequate fertiliser for agriculture
(iii)
minimise
the loss of nutrients
The studies will be performed at
two sites in the Mekong Delta in Vietnam which is a highly populated and
agricultural intense used / exploited area. In an interdisciplinary “bottom up”
approach we will analyse the present water management situation:
-
technology of drinking water supply
and waste water treatment
-
drinking water quality
-
tradition of inhabitants
(how and how much water is used, is there an acceptance for new technologies?)
-
costs of drinking water
supply
-
fluxes of nutrients
through the sites (imports and exports of nutrients and pollutants)
-
cropping system and
fertilizer demand
-
geoecological conditions (e.g. soil
quality)
Figure 1 shows the
nutrient fluxes that have to be analysed and the involved disciplines.
In Part 3 the working programs are
described in detail.
Figure 1: Fluxes and planned processes to be
optimised; the diciplines refer to the detailed workplan (see Part 3: Hy:
Hygiene (HyÖG), Ae: Agriculture (IPE), I: Industry (ith), S: Sociology (Soz.),
Wb: Water engineering (LWK), Geo: Hydrogeology (U+Oe).
The Mekong-Delta (MD) in
Vietnam is populated by about 17 millions of inhabitants on about 4 million
hectar land. In this area the main part of the vietnamese production of rice,
vegetable and fish takes place.
About 40-50% of the
inhabitants have access to fresh water and only about 30-35% access to treated
water (Lam Minh Triet and Nguyen Thanh Hung 2001). Most of the drinking water
plants are situated in bigger cities. If you look at the remote areas, only
about 9% of the population can get safe drinking water (Research Institute on
Strategy and Policy for Science and Technology Development. 2000. Challenges in
rural development in Vietnam). The reasons are low nfrastructure and relatively
high costs for water supply systems (Pollard & Hoang Thi Hoa, 2000).
Sustainable water supply
and water treatment does not only mean providing hygienically safe drinking
water and cleaned waste water. It also means recycling of nutrients (N, P, K)
and organic substance.
In developed countries
water treatment eliminates nitrogen, carbon and phosphorus. Here there are
mainly central plants in combination with a costly infrastructure. In areas
where there is not yet water supply and water treatment, decentralised concepts
are more advisable. It is sensible to implement water supply and waste water
treatment at the same time.
In developing countries
production of plants resp. food is the basis for living and income for the
majority in rural areas. To get a reliable and high agricultural production it
is necessary to use fertiliser and return organic carbon to the soils especially
for intense cultures like vegetable but also for rice. For low input agriculture
inorganic fertiliser is hardly affordable.
On the other hand the
use of black water as a fertiliser in tropical and subtropical agriculture is
hygienically unsafe especially when it is applied directly in the garden or when
irrigation water passes the rice field and runs directly into the river. If this
water is used for drinking water supply, there is a severe health risk for
humans.
Substrates of waste
water treatment are potential resources in developing countries that should be
used in agriculture (Sanchez et al., 1989). A treatment that provides -dependent
on the agricultural demands- the nutrients for agricultural will help farmers to
reduce their health risk (clean surface water for drinking water) and the use of
inorganic fertiliser (nutrients of the waste substitute inorganic fertilizer) (UNDP,
1996; Richter et al., 1995).
This is not only true
for low-input agriculture where appropriate substrates from waste water
treatment are a substitute for mineral fertiliser (Becker et al., 1995), but
also in high-input agriculture on minor places (e.g. areas of the Mekong
Delta). Organic substance can meliorate the soil by buffering acids, increase
the binding capacity for nutrients and improve the water retention potential (Mabeye,
1994).
The Mekong Delta, like
many developing countries faces big problems in waste water treatment and
drinking water supply. Waste water and organic waste seep into surface water or
fields without any pre-treatment. This means that
-
Organic fertiliser is lost.
-
Soil and surface water are contaminated
with pathogens.
-
Only part of the population have access
to drinking water which quite often is hygienically unsafe.
-
As a result this causes economic
problems like loss of income during illness and expensive cost for water and
fertiliser.
-
Additionally this causes ecological
problems: contamination of surface and ground water, use of precious ground
water, infiltration of uncontaminated ground water by connection between
different groundwater layers as a result of uncontrolled building wells, soil
degradation.
For drinking water,
different sources are used.
Rain water
is used as drinking water. Problems can occur when collection or storage lead to
any inoculation with pathogens. Also the availability of rain water may be too
low during the “sunny season”.
Ground water
out of uncontrolled wells in the Mekong Delta is frequently used as drinking
water. Usually there is no examination whether these wells provide suitable
dinking water. Neither there is a periodic control of the water. Aquifers close
to the surface are contaminated with agrochemicals like fertiliser and
pesticides (Le Quy An 2000, Tran Duc Kham 1988, Minh et al. 1997a). For deeper
layers uncontrolled wells represent a big risk of contaminating ground water by
connecting non-contaminated with contaminated groundwater layers.
The increase of saline
ground water also shortens the amount of available drinking water (SIWRMP
1995).
Furthermore the flooding
of big areas in the Mekong Delta ( about 1,2-1,9 Mio. ha) which occurs every
year can also lead to a contamination of ground water wells by polluted surface
water.
Surface water
is used for irrigation, aquaculture and drinking. The multiuse of surface water
may lead to user conflicts i.e. aquaculture may pollute surface water and lead
to restriction in its use as drinking water. On the other hand aquaculture which
provides most of the proteins for the population is very sensible when to faecal
contamination
There are a lot of
negative effects caused by the yearly flood like destruction of houses and
pollution of groundwater wells. Some positive effects result out of
sedimentation (input of nutrients) and the washing out of acids of acid sulfate
soils which reduces their toxiticity (Minh et al. 1997 b).
In rural and poor areas
decentralised systems may improve the health situation, soil fertlility and
agricultural production. Additionally they may be implemented much faster
compared to centralised systems that need high investments.
2.4
Summary
Drinking water supply
So far water is treated
with aluminiumsulfate for flocculation and heat. However boiling cannot remove
all pathogens reliably. Thus, other systems may be introduced, i.e. a
combination of different filtring systems or UV-desinfection.
Waste
water treatment
For Black Water there
are several applicable technologies: anaerobic digestion, composting, urine
separation, vermiculture. These technologies have been used for animal
excrements first. Additionally (i.e. anaerobic digestion) some of them have been
extended to treat human excrements. However there is no knowledge about nutrient
fluxes and the use of the substrates as fertilisers.
Especially the existing
methods neglect the specific demands of the soils for agricultural production.
§
So far there is no integrated concept regarding
decentralised waste water and waste in the Mekong Delta
§
There are existing methods for decentralized
water management. These methods should be optimized in a way that drinking water
should be hygienically safe and substrates from waste water should contain as
much nutrients as possible for agricultural production. The WWTS have to match
the agroecological demands.
[
Intro |
College of Technology |
Office Information ]
|
