Newsletter and Technical Publications
<International Source Book On Environmentally Sound Technologies
for Wastewater and Stormwater Management>
3.2.3 Operation and maintenance
The existing drainage systems are generally quite old in the developing
countries in the Asia
Pacific Region. The physical condition of existing drainage systems is
deteriorating due to wear and tear, and neglect of maintenance. The rate of
replacement of old pipes is generally much lower than the rate of deterioration
of existing pipes, which means that not only will it be necessary to invest in
public sewerage to meet future demands, but also to step up investments for
rehabilitation of existing systems to prevent further deterioration of sewerage
and drainage services.
Serious constraints are caused by a general lack of equipment, spare parts,
chemicals, and funds for operation of pumping stations and other facilities. All
maintenance is carried out manually, and there is no motorised equipment
available for cleaning or flushing out sand, grit and debris accumulating in the
pipe. There is also a shortage of financial resources, trained personnel, and of
qualified staff for maintenance management.
Pipes have been laid at too flat a slope, and the curb inlets lack adequate
sand traps. These deficiencies together with lack of means or equipment for
hydraulic flushing contribute greatly to the difficulties of operating and
maintaining drainage system.
The existing combined sewers are likely to have serious groundwater
infiltration and sewerage leakage problems, which will further complicate proper
wastewater management in the future, whether combined or separate sewers are
Observation of system failure in most of the Asia Pacific developing
Failure in simple sewer systems
Systems are generally characterised by shallow sewer pipes with low
gradients. As a matter of fact, the topographical condition of many cities is
almost flat with a slope around 0-3% and height 6 m above sea level.
Consequently, these shallow systems should be maintained frequently to avoid
sludge accumulation in pipes. People have to open manholes every week and flush
with buckets of water. However, this maintenance procedure is time consuming and
causes damage to concrete manhole lids. Furthermore, for security reasons,
people block backyard paths by constructing gates. As sewer pipes are
constructed along these paths, workers sometimes can not gain access to desludge
blocked pipe sections.
The most popular individual sanitation facility of the area is the pour-flush
toilet connected to sewer lines. Almost, all houses are connected to sewer
lines, discharging grey and/or black water. However, it has been observed that
some households discharge to roadside gutters directly without any pre-treatment
for reasons ranging from avoiding connection costs to avoiding maintenance
Failure in private maintenance of sewer pipes
In many instances, entrusting the operation and maintenance of sewer pipes to
community organisations has been unsuccessful. They have allowed pipes to clog
up, causing people to connect wastewater discharge pipes directly to the
roadside gutter as mention above. A typical example is one instance where an
oxidation (stabilisation) pond was constructed to receive pumped wastewater as
the final treatment facility in the area. The pond was found to have been out of
service for many years, due to the pump being out of order. With the objective
to avoid the cost of replacing the pump, the sewer line was cut off just before
entering the pumping station. The total volume of grey and black water, which
had been collected from sewer lines in the area was diverted into the canal
adjacent to the empty stabilisation pond, from there it was ultimately
channelled into the nearby river.
||Clogging problems exit in sewer lines and roadside gutters.
||There is no organised O & M for sewerage and roadside gutters.
||The community has carried out desludging activities rarely.
||There is no periodical inspection in the area.
||The final treatment facility is out of order.
||All grey and black water is discharged to the canal directly.
There exist water born diseases like diarrhoea and skin infection.