Download EDWARDS 2008 Volume III Wastewater and excreta use in aquaculture

Volume III: Wastewater and
excreta use in aquaculture
Peter Edwards
Guidelines overview
1.
2.
3.
4.
5.
6.
7.
8.
9.
Introduction
The Stockholm Framework
Assessment of health risk
Health-based targets
Health protection measures
Monitoring and system assessment
Sociocultural, environmental and economic
aspects
Policy aspects
Planning and implementation
Definitions
„
Wastewater and excreta (waste)
„
„
domestic sewage without significant industrial effluents
excreta
„
„
faeces and urine
faecal sludge, septage and nightsoil
„
Direct and indirect use of waste
„
Aquaculture
„
„
fish, non-molluscan shellfish (crustaceans) and aquatic
plants
filter-feeding molluscan shellfish not considered
Historical overview
„
Waste-fed aquaculture centuries old in several countries in
East, South and Southeast Asia, especially China
„
Developed mainly by farmers and local communities to use
nutrients to produce aquatic food
„
Engineered wastewater treatment systems with aquaculture
„
„
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Germany from end 19th century
India from 1930s
China from 1950s
Vietnam from 1960s
Very few engineered systems developed recently
Wastewater-fed fish ponds in Munich, Germany
Wastewater-fed fish ponds with primary sewage
distribution canal in foreground in Kolkata, India
Wastewater-fed fish ponds in Wuhan, China
Wastewater-fed fish ponds in Hanoi, Vietnam
Overhung fish pond latrine in south Vietnam
Waste-fed aquaculture strategies
Harvesting fingerlings raised on wastewater in
Hanoi, Vietnam
Harvesting fish from a wastewater-fed fish pond in
Kolkata, India
Discharge of wastewater and water spinach
cultivation in Phnom Penh, Cambodia
Harvesting duckweed from a pond fertilized with
polluted surface water, Taiwan
Major hazards of waste-fed of waste-fed aquaculture
Hazard
„Excreta-related
pathogens
- Bacteria e.g.
Relative
importance
- Low to
medium
- Always high concentrations in gut
- Cross-contamination in kitchen
greatest risk
- Hygienic processing and cooking
reduce risk
- Low to high
- Risks lower for fish than plant
producers and consumers
- Nil to high
Restricted geographical ranges
- Risk where endemic and fish or
plants eaten raw
Salmonella
- Soil transmitted
helminthes e.g.
Ascaris
- Foodborne
trematodes
e.g. liver flukes
- Schistosome
trematodes
e.g. Schistosoma
Comments
- Nil to high
- Restricted geographical ranges
- Transmitted through water contact
Major hazards of waste-fed aquaculture (continued)
Hazard
Relative
importance
Comments
- Low to
medium
- Same as bacteria
- Viruses e.g.
hepatitis
- Low to
medium
- Same as bacteria
„Skin irritants
- Medium to
high
- Contact dermatitis
- Cause likely due to microbes and
chemicals
„Vector-borne
- Nil to
medium
- No specific risk associated with
aquaculture
„Excreta-related
pathogens
- Protozoa e.g.
Giardia
pathogens e.g. malaria
Major hazards associated with waste-fed aquaculture
(continued)
Hazard
Relative
importance
Comments
„Chemicals
- Antibiotics
- Nil to low
- Heavy metals
- Low
- Halogenated
hydrocarbons
- Low
- Not usually used in waste-fed
aquaculture
- May accumulate in fish or aquatic
plants but rarely to un safe levels
- Wastewater and excreta generally
low concentrations
Microbial quality targets for
waste-fed aquaculture
Health protection measures
Group
Measure
Produce
Worker &
consumer family
Wastewater and excreta treatment
Produce restriction
Waste application witholding periods
Control of trematode intermediate hosts
Depuration
Hygienic food handling, preparation
Post-harvest processing
Health and hygiene promotion
Produce washing, disinfection, cooking
+
+
+
+
+
+
+
+
+
Local
community
+
+
+
Health protection measures
(continued)
Group
Measure
Chemotherapy and immunization
Use of personal protective equipment
Safe drinking water at pond site
Sanitation facilities at pond site
Disease vector and intermediate host
control
Reduced vector contact
Restricted access to pond site
Produce
Worker &
consumer family
+
Local
community
+
+
+
+
+
+
+
+
+
+
+
+
Health and control measures in
waste-fed aquaculture
Produce restriction
„
Fingerlings
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High-protein animal feed
„
„
„
waste use in aquacultural nurseries to produce seed
seed grow-out to full-size table fish in separate systems without use
of wastes
waste use to raise duckweed or tilapia
feed to fish or livestock in separate systems without use of wastes
Benefits
„
„
reduced public health risk
‘lengthening of food chain’ may increase social acceptability of
waste use
Tilapia raised on septage as high-protein animal feed
Duckweed raised on wastewater to feed fish in
Khulna, Bangladesh
Trematodes - schistosomes
„
Schistosomes (blood flukes) infection by larvae penetrating
skin of people entering water for domestic, occupational or
recreational purposes
„
Complex life cycles involving intermediate hosts, mainly
snails
„
Restricted geographical range so present a risk where
endemic
Trematodes – schistosomes
(continued)
„
Global health burden of 200 million people, mostly in SubSaharan Africa
„
Limited direct waste-fed aquaculture in Africa but
indirect use occurs
„
Pockets of disease in Asia
Health protection measures for
trematode schistosomes
„
„
Difficult to control
„
domestic and wild animals may act as reservoirs
„
molluscides adversely affect fish
Protection achieved by combination of different
health protection measures
„
removal of vegetation effectively controls intermediate
host snail populations
„
chemotherapy effective against trematode infections
Sociocultural aspects
„
Positive correlation between occurrence of traditional waste
use in societies and their population densities in recent past
„
nutritional imperative in poor societies e.g. East Asia
(China), South Asia (West Bengal, India) and Southeast
Asia (Java, Indonesia)
„
better chance to introduce waste-fed aquaculture in poor
communities to contribute towards increased incomes
and food security?
Poor wastewater-fed fish farmers, Kolkata, India
Transport of small fish harvested from wastewater-fed fish
ponds by poor traders for consumption by poor people,
West Bengal, India
Marketing low-cost fish from wastewater-fed ponds
in Kolkata, India
Socio cultural aspects (continued)
„
Reluctance or opposition to waste-fed aquaculture in
societies with improved social and economic status
„
Best example is China where waste-fed aquaculture is
traditional and previously widespread practice
„
nightsoil transported from cities to ponds in rural and
periurban areas
„
wastewater-fed ponds in periurban areas
Recent and dramatic decline in waste-fed
aquaculture, especially in China
„
Reduced availability of nightsoil through improved
sanitation
„
Domestic wastewater contaminated with industrial
sewage
„
Rapid urban expansion so land prices risen
„
Intensification of aquaculture reduced demand for
fertilizer
„
Consumers demand high-value fish rather than low-value
fish from waste-fed ponds (often tainted with phenols)
Pumping nightsoil into a barge for transport to farms
in rural areas in the mid 80s, Shanghai, China
Modern intensive aquaculture in Hangzhou, China
Domestic wastewater used to farm fish contaminated
with industrial sewage in Hanoi, Vietnam
Urban encroachment on waste-fed aquaculture in
Hanoi, Vietnam
Environmental benefits
„
Reduction of surface water pollution
„
Conservation or more rational use of water,
especially in arid and semi-arid areas e.g.
Australia and the Middle East
„
Reduction of risk of flooding in urban areas
as extensive pond areas act as buffers during
heavy rain
Economic and financial feasibility
„
Especially important for appraisal of viability of new schemes for waste
use in aquaculture
„
Some economic considerations
„ waste-fed aquaculture may be considered as low-cost waste
treatment system
„
„
costs of waste treatment offset by sale of fish or aquatic plants
Examples
„ model developed to calculate revenues for wastewater-fed
aquaculture in tropical and subtropical areas based on R & D in
Lima, Peru
„
integrated agriculture/forestry – fish culture in Kolkata, India
R & D on wastewater-fed
aquaculture in Lima. Peru
Vegetables and trees fertilized with wastewater-fed
fish pond water in Kolkata, India
Recommended wastewater-fed fish
pond design (Annex 1)
„
Concept of minimal wastewater treatment in stabilization
ponds for maximal production of microbially safe fish
„
Design takes into consideration extremely rapid die-off of
enteric bacteria and viruses in ‘green water’ ponds
„
No maturation ponds, only anaerobic, facultative and fish
ponds
„
Total pond area of 6.25 ha is 7X larger than a conventional
WSP to treat wastewater only