Africa Water, Sanitation & Hygiene Africa Water & Sanitation & Hygiene Nov-Dec 2017 | Page 24

Wastewater Use
Box 1: Tunisia: Water Reuse
Tunisia, with per capita freshwater availability of about 450 cubic meters a year, is recognized as a leader
in the area of treated wastewater reuse. From 1996 to 2030, the share of treated wastewater as a per-
centage of total available water resources is projected to more than double from 4.4 percent to 10.9 per-
cent. Despite strong institutional support, including the 2002 consolidation of the Ministry of Agriculture,
Environment, and Water Resources to oversee integrated water management and water reuse, only 18
percent of reclaimed water is currently used.Treated wastewater use has faced several constraints�social
acceptance, salinity levels too high for some crops, restrictive regulations, and volumetric pricing in the
range of US$0.02 to $0.05 per cubic meter (between 50 percent and 95 percent of the cost of freshwa-
ter for irrigation)� and these have limited its full potential for development.Through its carefully phased
approach to treated wastewater use and the concomitant development of a regulatory framework pro-
hibiting untreated wastewater use,Tunisia has significantly mitigated environmental and public health risks
associated with the practice elsewhere in the world.
Source: Authors.
Key to the success of planned strategic reuse programs
are a coherent legal and institutional framework with
formal mechanisms to coordinate the actions of multi-
ple government authorities; policies to reduce waste
loads through application of the “polluter pays” princi-
ple; appropriate practices for wastewater use through
crop choice, landscaping, and the like; public aware-
ness campaigns to establish social acceptability for
reuse; and consistent government commitment over
the long term.
The private sector can play an important role in promot-
ing treated wastewater reuse. It would be even more
attractive for the private sector to invest in wastewater
treatment when markets for the treated effluent exist.
This arrangement requires policies and regulations that
allow the private sector to function and provide reliable
services. For example, in Australia, the private sector,
under a contract to the city government, constructed a
treatment plant and pipeline (the “Virginia pipeline
scheme”) to transport treated wastewater to farms for
irrigation at an agreed tariff. This commercial solution
was successful, and the private investor considered fur-
ther investment to expand the treatment plant to serve
other irrigated areas.
LESSONS LEARNED
Based on international best practices, the following
should be borne in mind when developing wastewater
investment plans.
• Wastewater treatment must result in water quality
that is suitable for the particular reuse application—
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for example, nutrient removal may be counterproduc-
tive unless enrichment or eutrophication of surface or
coastal waters is a risk.
Guidelines linked to reuse must adequately protect
human health. The international standard WHO
guidelines (WHO 1989) are being revised, based on
the Stockholm Framework encouraging flexible, step-
wise implementation of guidelines that consider other
sources of risk.
Source control of contaminants is a must, particularly
for industrial wastewater; otherwise reuse programs
will be unsustainable.
Cultural values play an important part in the accept-
ability of water reuse, particularly where religious
views on ritual purity are highly articulated, for exam-
ple in Islam and Hinduism.
Sustained, long-term public awareness campaigns
among the reuse target group (such as farmers or
urban landscaping authorities) are needed for accept-
ance of water reuse.
Irrigation methods must be suitable for the type of
reclaimed water (high suspended, dissolved solids).
Where possible, highwater-productivity drip irrigation
should be encouraged. Sprinklers can lead to airborne
transmission of viruses and other contaminants. It
should be stressed that to save water, reuse must sub-
stitute for an existing use.
Crop restrictions applied sensibly may be essential,
particularly in view of increased phytosanitary con-
trols required in export agriculture.
Institutional coordination is essential among various
government authorities, civil society, and farmer asso-
ciations of water user groups.
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Africa Water, Sanitation & Hygiene • November - December 2017