Newsletter and Technical Publications
<International Source Book On Environmentally Sound Technologies
for Wastewater and Stormwater Management>
3.4 Reuse (Topic d)
Most of the Asia Pacific countries are tropical countries and their water
resources are not very limited. As a result, most of the developing countries do
not reuse wastewater except India, China and Vietnam where wastewater is being
used for irrigation.
In India, studies on the productivity of crop production have found that
recycling and reuse of nutrients and other valuable materials in domestic and
industrial wastewater is an effective method for utilising the wastewater.
General utilisation of wastewater through reuse and recycling has become very
important. In fact, wastewater is a resource rather than a waste since it
contains appreciable amounts of nitrogen, phosphorus and potash. Stabilisation
ponds can be used for fish aquaculture and the effluent can be used for
cultivation of short-term and long-term, ornamental, and commercial and fodder
Wastewater treatment and reuse improves water use efficiency. Wastewater has
been adopted as one of the major water resources nationwide, especially in the
northern area of coastal cities in China.
Practical experience in China has shown that wastewater reuse not only
reduces the demand for fresh water but also can improve environmental quality.
Reuse of treated wastewater has the following benefits: make up water supply
(reduces demand on good quality water); reduces the wastewater discharge thus
reducing water pollution; results in economic efficiency due to lower water cost
compared to transporting water from a distant source.
The main potential applications for reuse of treated wastewater in China are
in the following fields:
* Agricultural use through irrigation of crops as well as for improving
* Industrial cooling especially in the large industrial enterprises;
* Reuse in municipal public areas such as watering lawns and trees;
* Flushing toilets in hotels and residential districts;
* Reuse of the treated wastewater for urban landscape purposes.
Many municipalities set wastewater reuse as a strategy to meet the increasing
water demand. To identify the alternatives of wastewater reuse as well as their
feasibility and implementation, some cities where water shortage and pollution
are very serious such Beijing, Tianjin, Taiyuan, Dailian and Qingtao have been
selected as pilot areas for this particular purpose.
In Beijing the main purpose for reuse of treated wastewater is in
agricultural production during the irrigation season and to improve river
amenity. Some 487 m3/d of treated wastewater that meets the standard will be
available for reuse by 2005, replacing the existing untreated effluent and
providing the potential for reducing existing reliance on groundwater resources.
A project of wastewater reuse for industrial cooling purpose has been
completed and will be put in to operation soon.
Treatment and reuse of wastewater of a guest house in Jinan city in Shandon
Province is an example of reuse of treated wastewater for non-potable purpose in
the water shortage area.
The rotating disc biological treatment followed by filtration and
disinfection is used for treating the effluent from a hotel. The treated
wastewater is reused for watering grasses, make up water of a lake, washing cars
and flushing the toilet.
A wastewater reuse treatment plant with a capacity of 50,000 cubic meters per
day was built in Tai An city, in which a part (20,000 cubic meters per day) is
reused for industrial cooling and landscape purposes after reclamation by
In 2000 the municipal wastewater treatment rate will be more than 20 % of
total discharged wastewater, and the reuse rate to 10% of municipal wastewater
treated in the whole of China. It is forecast that the reuse rate of treated
municipal wastewater in 2020 will be up 3-49% in small and medium sized cities
and cities with a shortage of water (Lin 1999).
Reuse of wastewater occurs most effectively with on - site or small scale
treatment systems. Thus implementation of reuse options in the local context
with local community consultation must be seriously considered. Indeed many
Western Australian householders are already engaged in the practice of recycling
greywater. Greywater is defined as untreated household wastewater, which has not
come into contact with toilet waste. It can originate from the shower, bath,
bathroom, washing basin, clothes washing machine and laundry trough. The
criteria associated with greywater recycling solely for irrigation, as distinct
from combined black and grey water reuse, may be less stringent.
A number of greywater recycling installations are also currently in use in
Western Australia such as:
- Urban parkland, sports grounds, golf courses etc.
||- Surface infiltration,
|Private garden reuse
|Disposal via constructed wetlands to
||- Direct to water supply
- Indirect via groundwater
In the developing countries nightsoil has been used as fertiliser. Nightsoil
from buckets and latrines is generally collected by private contractors and sold
to farmers, or collected directly by the farmers. Farmers use the nightsoil as a
fertiliser and soil conditioner and apply it to agricultural areas without
pre-treatment. The urban public service and environmental companies frequently
collect nightsoil from pubic toilets with bucket latrines, which is also sold to
This use of untreated nightsoil is illegal according to current environmental
legislation, but the enforcement is overlooked. The Vietnam Wastewater Planing
for Urban Areas study, reports that infestation rates of intestinal parasites
are more than 95% in areas that use nightsoil in agriculture.
Exact information about the quantities of sludge and nightsoil collected and
disposed of by public and private companies is not known. However, Table 3.14
gives information about the average quantities collected from each household
according to each city classification. There are insignificant regional
differences in sludge and nightsoil collection rates. The relatively large
difference in sludge collection rate per household for the various city classes
may be the result of several households sharing toilet facilities, and that the
survey has not been able to differentiate between houses with own and households
sharing in-house toilets. This situation is believed to be more prevalent in the
larger cities with blocks of flats. Nightsoil collection rates are, on the other
hand, considerably higher per household in the smaller cities, but city sample
size may be too low to give an accurate estimate.
Table 3.14: Quantities of septic sludge and nightsoil collection
Septic tank sludge
|Source: Vietnam National Urban Wastewater
and Sanitation Strategy Nov. 1995.