Blanca JimenezBlanca JimenezTreatment and Reuse Group Treatment and Reuse Group

Institute of Engineering, UNAM-MexicoInstitute of Engineering, UNAM-Mexico

GUIDELINES FOR THE SAFE USE OFWASTEWATER, EXCRETA AND

GREYWATERVolume 2

Wastewater use in agriculture

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 FertilizerSource: 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).

BackgroundWHO (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 standardsNo 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

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

The Stockholm FrameworkIntegrated approach that combines risk assessment and risk management to control water related diseases

Basis

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 diseasei.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 mLNo 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 0-4 years 5-80+years All ages

Developed 0.2-1.7 0.1-0.2 0.2-0.4

Developing 2.4-5.2 0.4-0.6 0.8-1.3

World 3.7 0.4 0.7

Source: WHO, 2006 (adapted from Mather et al., 2002)

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

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

MicrobiologyMETHODOLOGY (QMRA)

Epidemiology

SEVERAL OPTIONS to control risk

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 onA 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 sitehttp://www.personal.leeds.ac.uk/~cen6ddm/Reuse/Reuse%204_published/Wastewater

%20reuse%204_files/Default.htm

Quantitative Microbial Risk Analysis (QMRA)

Element/compoundSoil concentration

Organic compoundSoil concentration

(mg kg−1) (mg kg−1)

Antimony 36 Dichlorobenzene 15

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 Heptachlor 0.18

Fluorine 635 Hexachlorobenzene 1.40

Lead 84 Lindane 12

Mercury 7 Methoxychlor 4.27

Molybdenum 0.6 PCBs 0.89

Nickel 107 PAHs (as benzo(a)pyrene) 16

Selenium 6 Pentachlorophenol 14

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

Chlorodane 3 Tetrachloroethylene 0.54

Chlorobenzene 211 Toluene 12

Chloroform 0.47 Toxaphene 0.0013

Trichloroethane 0.68

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.

Definition of the tolerable risk

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

Notes

Wastewater treatment 1-6 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

• Because normally microorganisms content in wastewater is very high what it is defined is log

removal/inactivation

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

Less treatment implies more supervision sites

Washing = More public involvement

Involuntary soil ingestion from farmers

Developing countries

Developed countriesCalifornia Title 22 ≤ 2.3 FC/100 ml (virtually Zero) ONLY with

treatment

Monitoring WWTP at T level

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

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 standardsEach countries can select the disease caused through agricultural irrigation in their region to controlEach 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 stepHO are a key parameter to control, BUT, since the 1989 guidelines the lack of capacity to measure this parameter is evident in several countries