As Asian cities expand and invest billions in sewage plants, waste facilities and power stations, one technical question has major environmental consequences: how accurately are we measuring pollution before it leaves the pipe or chimney?
A new report from the Asian Development Bank argues that too much attention is given to computer models that predict how pollution spreads, and not enough to calculating how much pollution is actually produced in the first place. Dispersion models for air and water are only as good as the data fed into them. If the numbers at the source are wrong, the final predictions will also be wrong.
Drawing on methods used by institutions such as the Intergovernmental Panel on Climate Change, the European Environment Agency and the United States Environmental Protection Agency, the report makes a clear point: get the basics right. Measure or estimate emissions properly before modeling their impact.
Cleaning Up Cities Starts With Sewage
Urban sanitation is one of the biggest infrastructure priorities in developing countries. Wastewater treatment plants are designed based on assumptions about how much water people use and how polluted that water is.
Many countries still use standard estimates of 120 to 150 liters of water per person per day. Around 80 to 90 percent of that becomes wastewater. If these numbers are too high, treatment plants may be oversized and waste money. If too low, plants can become overloaded and release untreated sewage.
The good news is that domestic wastewater is fairly similar around the world. It usually contains predictable levels of organic matter, suspended solids, ammonia and phosphorus. This makes it possible to use tested “rules of thumb” when designing treatment systems.
The report also highlights sludge and odor as growing challenges. As more sewage is treated, more sludge is produced. Handling and disposing of it properly is essential. Odor, especially from sludge storage and drying, is often what nearby residents notice first. Measuring and controlling these emissions is critical for public acceptance.
The Hidden Risks of Landfills and Waste
Municipal solid waste creates another set of pollution problems. In landfills, rainwater mixes with decomposing waste to produce leachate, a highly polluted liquid that can contaminate groundwater if not managed properly.
The report explains that estimating leachate volume does not always require complex modeling. Practical experience from similar landfills often provides reliable estimates. However, local conditions such as rainfall and waste composition must be considered.
Landfills also emit methane, a powerful greenhouse gas. International guidelines provide formulas to estimate methane generation over time. But for project-level decisions, simpler emission factors based on local data can often determine whether a landfill exceeds reporting thresholds.
Biotreatment methods such as composting and anaerobic digestion can reduce landfill use, but they also produce wastewater and odors. Digestion plants, for example, can generate large amounts of high-strength wastewater during pretreatment. Composting, especially in simpler systems, may produce leachate if moisture is not well managed. Again, careful estimation and monitoring are key.
Incineration and Power Plants Under the Microscope
Waste-to-energy plants and thermal power stations are often promoted as modern, cleaner solutions. But they still generate emissions that must be carefully measured.
Incineration reduces waste volume significantly, yet it produces bottom ash and fly ash that still require safe disposal. Flue gases can contain nitrogen oxides, sulfur dioxide, particulate matter and trace pollutants such as heavy metals. These emissions can be estimated using three main approaches: data from similar plants, standard emission factors or calculations based on fuel composition and pollution control efficiency.
Thermal power plants, especially gas- and biomass-fired units, also require detailed emission estimates. Sulfur dioxide can be calculated from fuel sulfur content. Particulate matter depends on ash and dust removal systems. Nitrogen oxides are more complex, often requiring emission factors based on operating data.
Water pollution is another concern. Cooling systems use large volumes of water, and some of it is discharged back to rivers or seas. Even when pollution levels are low, temperature and chemical additives must be controlled.
Modeling the Standard Is Not Enough
One of the report’s strongest warnings concerns a common shortcut in environmental assessments. Some studies use the legal emission limit as the input for dispersion models instead of a realistic estimate of what the plant will actually emit.
This can distort results. It may exaggerate impacts and increase costs, or underestimate real risks if actual performance is worse than assumed. Simply relying on guaranteed standards in contracts is not enough.
The report concludes that environmental impact assessments must influence project design early, when changes are still possible. Exact precision is not always necessary. What matters is using reasonable, evidence-based estimates that reflect real operating conditions.
In the end, effective pollution control begins not with complex models, but with honest and practical measurement at the source.