Transcript Blanca Jimenez Treatment and Reuse Group Institute of

GUIDELINES FOR THE SAFE USE OF
WASTEWATER, EXCRETA AND
GREYWATER
Volume 2
Wastewater use in agriculture
Blanca Jimenez
Treatment and Reuse Group
Institute of Engineering, UNAM-Mexico
70 % of the world water extracted is used for agriculture
75% of the irrigated area is located in developing countries
There is a high dependence on irrigation for food
production
(United Nations 2003)
Agriculture Freshwater Withdrawal in
2000
Blue water scarcity for 2025
Pumping Sewage on Crops for Fertilizer
Source: Harper’s Weekly, 1890, Photo IV.1;
from The Search For The Ultimate Sink by Joel A. Tarr,
The University of Akron Press, 1996
In 2006, still is a practice but…..
Strawberry Farm, Irvine, CA
The Mezquital Valley, México
At least 20,000,000 ha in 50 countries are irrigated with raw or
partially treated wastewater and
> 1/10 of the world’s population consumes crops irrigated with
wastewater.
Worldwide more than 800 million farmers are engaged in urban
and peri-urban agriculture (UNDP, 1996).
Background
WHO (World Health Organization) (1973), Reuse of Effluent:
Methods of Waste-water Treatment and Health Safeguards,
Technical Report 517, WHO, Geneva.
WHO (1989) Health Guidelines for the Use of Wastewater in
Agriculture and Aquaculture. Report of a WHO Scientific
Group, Technical Report Series No. 778, WHO, Geneva
Need
to update the guidelines taking into account recent
scientific evidence of effects, include changes in population
characteristics, changes in sanitation practices, better
methods for evaluating risk, social/equity issues and socio
cultural practices
WHO (2006) GUIDELINES FOR THE SAFE USE OF
WASTEWATER, EXCRETA AND GREYWATER
Objectives
To have criteria accepted worldwide
 (No more California Title 22 vs WHO)
To USEFUL, FLEXIBLE, LOCAL ADAPTED AND
IMPLEMENTABLE criteria to be used World wide
Main Characteristics
DIFFERENCES
It is a methodology to set up standards
 No guidelines values but health goals
Very explicitly recognized advantages of reusing
wastewater
Considers local capabilities and constraints
SIMILARITIES
Still proposed a high level of health protection
Structure
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Assessment of health risk
Health based targets
Health protection measures
Monitoring and system assessment
Socio cultural Aspects
Environmental Aspects (Positives and
Negatives)
Economical and financial Considerations
Policies aspects
Planning and Implementation
Basis
The Stockholm Framework
Integrated approach that combines risk assessment and risk
management to control water related diseases
Health concerns when wastewater is
reused to irrigate
The risk will
only be of public
health
importance IF it
increase the
incidence or
prevalence of
disease
i.e., importance
or impact is
different in each
region
Group
exposed
Infections risks
Helminths
infections
Bacterial/
viruses
Protozoa
Consumers
Significant
Increased if >104
TC/100 mL
No direct
evidence
Farm workers
and their
families
Significant
Increased if >104
TC/100 mL
Insignificant
Nearby
Communities
Not studied
for
sprinklers
Significant
with flow
and furrow
irrigation
Increased for
sprinkler
irrigation if >106-8
TC/100 mL
< 104-5 TC/100 mL
not associated
with viral
infections
No data for
sprinkler
irrigation
Difference in primary risks
Diarrhoeal disease incidence per person per year
Region
Developed
0-4 years
0.2-1.7
Developing 2.4-5.2
World
3.7
5-80+years All ages
0.1-0.2
0.2-0.4
0.4-0.6
0.4
0.8-1.3
0.7
For regions with low sanitation level and poor conditions:
Helminthiasis (several kind)
For regions with high levels of sanitation and public health:
Viruses, but as well some emergent diseases
Source: WHO, 2006 (adapted from Mather et al., 2002)
Definition of a tolerable risk
Based on local conditions (Public health level)
Priorities (types of diseases and relative
importance)
Capabilities (institutional, economical, social)
Assessment of Health risks
An actual risk exists if (ALL):
a) An infective dose of a pathogen reach a crop
or a a pathogens that arrive into a crop
multiplies on it to reach an infective doses
b) The infective doses reach a human host
(directly or indirectly through a vector)
c) The human host become infected
d) The infections doses cause disease or further
transmition
Type of
agriculture
Recommendation for
viruses, bacteria and
protozoan pathogens
Guidelines for Helminth ova
Unrestricted
≤10−6 DALY loss pppy
≤1/L (arithmetic mean) )
Restricted
≤10−6 DALY loss pppy
≤1/L (arithmetic mean)
Localized
≤10−6 DALY loss pppy
(a) Crops growing in or near
the soil :
≤1/L (AM)
(b) No recommendation for
crops growing above soil and
grown with drip irrigation
Microbiology
Epidemiology
METHODOLOGY
(QMRA)
SEVERAL OPTIONS to control risk
Quantitative Microbial Risk Analysis (QMRA)
The amount of pathogens that can be ingested
without exceeding a tolerable risk
As result, the permissible number of
microorganisms per L of wastewater that can be
used to irrigate a certain type of crop is obtained
Based on
A probabilistic calculation of catching an infection
from a single dose (d) of a certain pathogen (P),
i.e. evaluating P1(d) during several exposures
Done using mathematical models (Exponential
dose-response and the Beta-Poisson model) but
other models or different constants can be used
CONSULT Prof. Mara’s web site
http://www.personal.leeds.ac.uk/~cen6ddm/Reuse/Reuse%204_published/Wa
stewater%20reuse%204_files/Default.htm
Element/compound
Soil concentration
Organic compound
(mg kg−1)
Soil concentration
(mg kg−1)
Antimony
36
Dichlorobenzene
Arsenic
8
2,4–D
0.25
Barium*
302
DDT
1.54
Beryllium*
0.2
Dieldrin
0.17
Boron*
1.7
Dioxins
0.00012
Cadmium
4
15
Heptachlor
0.18
1.40
Fluorine
635
Hexachlorobenzene
Lead
84
Lindane
Mercury
7
Methoxychlor
4.27
0.89
12
Molybdenum
0.6
PCBs
Nickel
107
PAHs (as benzo(a)pyrene)
16
14
Selenium
6
Pentachlorophenol
Silver
3
Phthalate
13,733
Thallium*
0.3
Pyrene
Vanadium*
47
Styrene
0.68
Aldrin
0.48
2,4,5–T
3.82
Benzene
0.14
Tetrachloroethane
1.25
Tetrachloroethylene
0.54
Chlorodane
3
Chlorobenzene
211
Toluene
Chloroform
0.47
Toxaphene
12
0.0013
Definition of the tolerable risk
To standardized the acceptable
risk caused by different agents in
different norms (Drinking water a
risk of 10-5 for cancer while in
irrigation a risk of 10-3 for
diarrheas)
DALY = Disability-adjusted life year
1 Daly = 1 lost year of healthy life
and the burden of disease as a
measurement of the gap between
current health status and an ideal
situation where everyone lives into
old age free of disease and
disability
It combines in one measure the
time lived with disability and the
time lost due to premature
mortality.
WHO recommendation: ≤ 10-6 DALYs
lost
Is extremely safe, as people expect their
drinking water to be extremely safe
<<< than the actual incidence of diarrhea
disease in the World that is of 0.7, i.e, 10-1
For 1 person is equal to loose 31.5
seconds in a year ¡¡¡¡
But for a community means to loss 1 year
per million people
The desired level of protection can be reached
through a combination of management control
options such as:
–
–
–
–
Wastewater treatment
Crop restriction
The irrigation method
Food preparation
•
•
•
•
Washing
Disinfection
Peeling
Cooking
– Hygienic practices at food market
– Vaccines and medication, etc…..
Hence
– Methodology/criteria defines the total
removal/inactivation efficiency needed to be achieve
(examples are provided in Vol 2)
– How to reach it is a national decision
Pathogen reduction (log units) achieved by health
protection control measures
Control Measure
Pathogen
log
reduction
Wastewater treatment
1-6
Notes
The required pathogen removal in a WWTP depends on the
combination of the health protection measures
Localized irrigation
(low-growing crops)
2
Root crops and crops such as lettuce that grow just above, but
partially in contact with the soil
Localized irrigation
(high growing crops)
4
Crops, such as tomatoes, the harvested parts of which are not in
contact with the soil
Spray/sprinkler
drift control
1
Use of micro-sprinklers, anemometer controlled direction switching
sprinklers, inward –throwing sprinklers, etc
Spray sprinkler
buffer zone
1
Protection of residents near spray or sprinkler irrigation. The buffer
zone should be at least 50-100m
Pathogen die-off
0.5-2 per
day
Die-off on crops surfaces that occurs between last irrigation and
consumption. The log unit reduction depends on climate
(temperature, sunlight intensity , crop type, etc.)
Produce washing
1
Washing salad crops, vegetables and fruit with clean water
Produce disinfection
2
Washing salad crops, vegetables and fruit with a weak disinfectant
solution and rinsing with clean water
Produce peeling
2
Fruit and root crops
Produce cooking
5-6
Immersion in boiling water until the food is cooked ensures
pathogen destruction
Examples options for the reduction of viral, bacterial and protozoan
pathogens that achieved a health based target of ≤10-6DALYS pppy
Less treatment maybe more economical
Washing = More public involvement
California Title 22 ≤ 2.3 FC/100
ml (virtually Zero) ONLY with
Developing countries
treatment
Developed countries
Less treatment implies more supervision sites
Monitoring WWTP at T level
Involuntary soil ingestion from farmers
•
Because normally microorganisms content in wastewater is very high what it is defined is log
removal/inactivation
Monitoring
Urban areas: 1 sample each two weeks for E.
coli and 1 sample per month for Helminth ova
Rural areas: 1 sample each 1−6 months for
helminth ova
For pathogens, instead of measuring an
INDICATOR (Thermoloterant coliforms) can be
used
Helminth eggs
≤ 1 Helminth egg/L for both restricted and
unrestricted irrigations
 EXCEPT for drip irrigation+high growing crops (crops
not growing down or on the soil), for this case there is
NO recommendation
When children under 15 are exposed to
wastewater in farmer fields additional control
measures (antihelminthic chemotherapy) are
recommended to be followed IF there are
evidence of damages
(b)
Data from full scale
plants
(c) Theoretical efficiency
based on the removal
mechanisms
(d) Data from tests with up
to 2 log units initial;
removal might be greater
than that reported or not
(e) Data from Laboratory
Tests
•
•
•
•
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•
Chapter 8 Environmental Aspects
Wastewater as an important source of water and nutrients
Uses soil capacity to remove pollutants
Can cause side effects if not planed
Has Negative but also POSITIVE impacts
Chapter 9 Economical and financial consideration
(for encouraging safe use of wastewater)
Chapter 10 Policy Aspects Clear National Policy
Appropriate legal framework, Adequate Institutional
Framework, Appropriate and implementable regulations,
Chapter 9 Planning and Implementation
Strategies including elements on communication and
interaction with stake holders and the collection and use
of data for retrofitting
Summarizing
Not fixed values but a Methodology to set up
standards
Each countries can select the disease caused
through agricultural irrigation in their region to
control
Each country can even vary the level of
protection desired based as long as it
progressively tends to the goal proposed
Flexibility to control risks allows economical
costs optimization
End Notes
WHO criteria is to protect HEALTH, and had nothing to
do to protect soil, groundwater can crop productivity
(attention need to be put when wastewater contains
important amount of industrial wastewater)
Who guidelines recognizes the beneficial reuse of
wastewater to increase crop production as long as health
is protected
The 10-6 DALYs goals is still very protective and may
not be unachievable in some countries as first step
HO are a key parameter to control, BUT, since the 1989
guidelines the lack of capacity to measure this parameter
is evident in several countries