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Wastewater reuse for agriculture irrigation –
a sustainable solution for a better tomorrow?
Yuh Nien Chow, Lai Kuan Lee, Nor Azazi Zakaria, Keng Yuen Foo, Researchers, River Engineering and Urban
Drainage Research Centre (REDAC) and School of Industrial Technology, Universiti Sains Malaysia (USM), Malaysia
T
he pressing need for clean, potable water, due to
climate change, demographic growth, economic
development, rising living standards and envi-
ronmental pollution, has become the most critical global
agenda. In some parts of the world, water demand has
been rising more than twice as fast as population growth.
Annual water withdrawal has suffered in excess of a six-fold
increase, from less than 600km
3
/year at the beginning of
the twentieth century to greater than 3,800km
3
/year at the
beginning of the twenty-first century. Agriculture uses the
largest amount of water, accounting for approximately 75%
of the available water supply. The dominance of agriculture
has been unquestioned up until recently, but the lack of
fresh water resources is expected to intensify problems of
water scarcity, food security, water sanitation, and health.
These global changes have urgently prompted the possibil-
ity of wastewater reuse as the best available option for food
crop irrigation practice. Implementation has been widely
practiced in developed cities including Berlin, London,
Milan and Paris, with approximately 20m ha of agricultural
land irrigated with untreated, partially treated or treated
wastewater. In developing regions such as Pakistan and Viet
Nam, more than 26% and 80%, respectively of national crop
production is supported by wastewater from the urban and
peri-urban areas. Similarly, in Ghana and Mexico, informal
irrigation using diluted wastewater has been performed on
plantation areas exceeding 11,500 and 260,000 ha, respec-
tively. In Malaysia, the agricultural sector has been a driver
of economic development, accounting for 9.3% of national
GDP. With annual rainfall of more than 2,800mm/year, and
a total surface water volume of 566bn m
3
, this is sufficient to
meet domestic, industrial and agricultural demands.
In addition to the huge saving and preservation of fresh water,
a wastewater reuse strategy would help reduce waste effluents
and preserve fresh water ecosystems. Nevertheless, it is possi-
ble that the available water resources, which rely primarily on
river water, could be severely polluted by a wide range of devel-
opment projects. According to Datuk Hanapi Mohamad Noor,
former director of the Department of Irrigation and Drainage
(DID), Malaysia, the major rivers in Malaysia, notably the
Klang, Juru, and Pahang rivers, are heavily polluted by domes-
tic and industrial discharges, but have been the primary source
for irrigating a variety of food crops.
These sewage and industrial wastewaters that contain
a broad range of organic pollutants and heavy metal ions,
including zinc, copper, lead, manganese, nickel, cadmium,
and chromium ions, have been associated with the long term
accumulation of toxic contaminants in the soil structure.
These contaminants reach the plants, and subsequently the
food chain, creating a large-scale dietary hazard with the
accumulation of heavy metal toxicity in the major organs of
the human body, specifically the kidneys, bones and liver.
Lead, arsenic, mercury, copper, zinc, and aluminium poison-
ing are related to gastrointestinal diseases such as diarrhoea,
stomatitis, tremor, and haemoglobinuria, inducing a rust-red
colour to the stool, and causing ataxia, paralysis, vomiting,
convulsion, depression and pneumonia. The nature of the
contamination could be toxic, neurotoxic, carcinogenic,
mutagenic or teratogenic, according to the duration and dose
of exposure.
Over the years, the outbreak of heavy metals-induced
food toxicity have been widely reported. The incidence of
mercury poisoning was recorded in Minamata, Japan as
early as the 1950s. It was found that the poison intensifies
the degeneration of nerve cells in the brain, and mentally
retards the victims’ offspring, a condition that could be
persistent for more than a generation. In 1964, an endemic
illness known as blackfoot disease was discovered in Taiwan,
due to the presence of arsenic in the deep well waters. In
Japan, over 12,000 infants were poisoned by arsenic-
contaminated dry milk, resulting in the death of more than
120 babies. In Malaysia, cases of food poisoning have been
rising to a worrying extent. It has been reported by the Ipoh
Municipal Council of Malaysia that dried prawns and cuttle-
fish imported from Thailand were found to contain a high
level of arsenic, exceeding the permissible level of 1mg/L.
Another incidence of food poisoning was recorded in Negeri
Sembilan, where pig farm effluents were discharged into the
Sepang, Lukut, and Linggi rivers, to create contamination by
copper, zinc, and lead ions.
In Kedah and Perlis, there was found to be a wide varia-
tion in the concentration of heavy metals in the paddy fields,
such as iron, manganese, zinc, chromium, lead, copper and
cadmium. Also, leafy vegetables cultivated in the farmlands
of Kuching, Sarawak, were found to contain a higher accu-
mulation of heavy metals compared to other vegetables.
Through a series of in-depth investigations it was found