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United Nations Environment Programme
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<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 used.

Observation of system failure in most of the Asia Pacific developing countries

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 responsibilities.

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.

In general

1) Clogging problems exit in sewer lines and roadside gutters.
2) There is no organised O & M for sewerage and roadside gutters.
3) The community has carried out desludging activities rarely.
4) There is no periodical inspection in the area.
5) The final treatment facility is out of order.
6) All grey and black water is discharged to the canal directly.
7)

There exist water born diseases like diarrhoea and skin infection.

 

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