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United Nations Environment Programme
Division of Technology, Industry and Economics
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State of Waste Management in South East Asia


E. Industrial Wastewater

In Southeast Asia, there is a high incidence of untreated industrial wastewater being discharged into sewers and natural water bodies, although most of the countries require that industrial wastewater should be treated before discharge. This happens because government monitoring, control and enforcement of environmental regulations is either missing or inadequate. There is, therefore, increasing concern over groundwater being polluted with nitrates and micro-organisms in the leachate from industrial landfills or dumps.

Vietnam has a wastewater treatment plant in Hanoi for tannery wastewater It is a UNDP demonstration project for training purposes. But the factory is not in operation due to lack of raw materials. On the other hand, in Singapore, most industries discharging wastewater have treatment facilities for pre-treatment before discharging wastewater into the combined sewer system. Including its waterworks sludge treatment plants, Singapore has in its records a total of 2,438 industrial wastewater treatment plants, 40 percent of which are oil interceptors. In many of the ASEAN countries, the industrial wastewater is discharged into a holding tank or retention pond, which allows some degree of sedimentation and initial surface oxidation activity to take place before the wastewater is finally discharged into the receiving waters.

Depending on the hydraulic retention time and the raw wastewater characteristics, this process is generally not viewed as sufficient to improve the quality of the wastewater to acceptable levels.

The common treatment systems used for industrial wastewater in ASEAN countries include:

  • Oil interceptors – physical systems to capture oily discharges, allowing separation of oil from water,
  • Balancing/equalization tanks – to homogenize variations in wastewaters over time or from different sources,
  • Sedimentation/settling/clarifying systems - physical systems to enable the separation and removal of settleable solids from the water,
  • Neutralization systems – adjustment of pH , acidity or alkalinity of the wastewater, to required levels for further treatment or discharge
  • Chemical treatment systems – chemical process to either precipitate out the polluting compound (e.g. a heavy metal like copper) or cause destruction of the pollutant (e.g. cyanide) so that these can be removed from the treated wastewater, using coagulants/flocculants,
  • Activated sludge systems – a biological treatment system to reduce the organic pollutants in wastewater,
  • Biological filtration systems – uses biological growth to reduce organic pollutants in wastewater being filtered,
  • Ion exchange systems – used for removing inorganic pollutants, normally complex compounds of heavy metals in wastewater,
  • Activated carbon absorption –used for reducing fine organic contaminants, such as color pigments and odor-causing organic pollutants,
  • Other aerobic and anaerobic systems – a large number of technologies are available in the form of biological systems, with aeration (aerobic), or in the absence of oxygen (anaerobic).

Depending on the characteristics of the wastewater stream, various combinations of the above-cited systems may be employed by different industries in the ASEAN countries to enable the treated wastewater to:

  1. be released into the sewer for further treatment with municipal wastewater (e.g. in Singapore); or
  2. be discharged into waterways but in compliance with regulated water discharge standards.


An associated issue in wastewater management is sludge management. Disposal of organic sludge is usually not regulated since it can be easily disposed of in the landfills or recycled in composting. The problem is disposal of chemical or inorganic sludge. In Malaysia, sludge is considered scheduled (or hazardous) waste, which has to be further treated before being approved for disposal. In Singapore, chemical sludge can be easily disposed of in landfills after fixation.

In many of the ASEAN countries, sludge is not treated but simply disposed of in local landfills. Because of a growing concern for potential environmental and health impacts from sludge, local governments are looking at ways to improve the system of sludge management but are constrained by limited resources.

F. Storm Water

In most of the ASEAN countries, storm water is discharged into the nearest water course and not into the sanitation systems that are usually designed to receive runoff generated by tropical thunderstorms. In the less urbanized areas, storm water is allowed to seep into the ground and also discharged into the nearest watercourse.

Data and records of storm water quantities, quality and incidences are lacking in many of the ASEAN countries, making it difficult to design the management of storm water. In the absence of the necessary information, in Malaysia, the Department of Irrigation and Drainage under the Ministry of Agriculture has resorted to the issuance of mandatory guidelines on urban storm water management for all local authorities.

Some current practices in storm water management in ASEAN are listed in Table 7 below

Table 7: Current Storm Water Management Practices
Purpose Method Reason Countries
Peak flow attenuation
- Storm monitoring
- Detention/channel storage
- Gravel surfaces
- Flood prediction
- Flood routing
- Retardation
- More developed ASEAN countries
Runoff volume reduction
- Retention storage
- Diversion
- Soakaways
- Removal of flow
- Subtraction of flow
- Infiltration
- All ASEAN countries
Provision for flooding
- Flood warning
- Evacuation or diversion
- Countries with seasonal flood potential, e.g. Malaysia
Catastrophe aversion
- Evacuation
- Sandbagging
- Emergency overflows
- Weir strengthening
- Water tanks
- Structural failure
- High water levels
- Water flow control
- Dangerous flood levels
- Polluted water suppliers
- The more developed ASEAN countries
Erosion control
- Vegetation
- Rockfill
- Mulching
- Settling basins
- Sediment removal
- Screen
- Contour ploughing
- Stabilization, retardation
- Flow control
- Flow control
- Catchment sediment
- Basin renewal
- Detritus
- Surface storage
- Most of the developing ASEAN countries
Pollution Control
- Street sweeping
- Street vacuuming
- Refuse removal
- Summons or fines
- Grass street verges
- Catching solids
- Catching fines
- Avoidance of pollution
- Disincentive
- Catching fines, scum
- All of the countries (street vacuuming only in countries like Singapore)

G. Mixed Waste

In the developing countries of ASEAN where infrastructure and management accountability for waste management are lacking, the kind of waste that lands in municipal or public dumpsites and landfills is totally mixed waste. Mixed waste is the result of lack of differentiation of the sources of wastes. More often than not, mixed waste contains hazardous components, which can be harmful to the environment and most of all to the workers and scavengers at the landfills and the residents in the vicinity.

Mixed waste are breeding grounds of disease-carrying vectors like mosquitoes. They can contain toxic wastes, e.g. solvents, poison, heavy metals, and other chemicals that could leach into the groundwater and contaminate major source of drinking water. And should a fire breakout in the landfill or dumpsite, the toxic substances could produce air pollutants that would adversely affect the air quality of the neighborhood.

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