water quality

Water quality dwindles worldwide as pollution rises.

By: Staff Reporter
Pathogen and organic pollution due to the respective discharge of untreated wastewater and organic compounds are now a serious threat across rivers in Asia, Africa and Latin America, says UNEP.

A United Nations Environment Programme (UNEP) pre-study – A Snapshot of the World’s Water Quality: Towards a global assessment has found that water pollution has risen across three continents-Asia, Africa and Latin America, putting hundreds of millions of people at risk.

The WWQA pre-study, conducted in 2013-2015, was initiated by the UN-Water Thematic Priority Area on Water Quality and led by the United Nations Environment Programme (UNEP) with several regional partners.

Population growth, increased economic activity, the expansion and intensification of agriculture, and an increase in the amount of untreated sewage discharged into rivers and lakes are the main reasons behind the troubling rise in surface water pollution in Asia, Africa and Latin America. The rise in the pollution of surface waters threatens to damage vital sources of food and harm the continents’ economies. By making access to quality water even more difficult, water pollution also threatens to breed further inequality, hitting the most vulnerable – women, children and the poor – the hardest.

Noting that the increasing amount of wastewater being dumped into our surface waters as deeply troubling, the report has called on all nations to come together “to combat this growing menace”.

According to the Report, pathogen and organic pollution rose in more than 50 per cent of river stretches from 1990-2010 in all three continents, while salinity pollution has risen in nearly one third, the UNEP states.

Pathogen pollution

Severe pathogen pollution, the rise of which is largely down to the expansion of sewer systems that discharge untreated wastewater into surface waters, is estimated to affect around a quarter of Latin American river stretches, around 10 to 25 per cent of African river stretches and up to one-half of Asian river stretches.

In some countries, more than 90 per cent of the population relies on surface waters as their source of drinking water. These waters, which are also used to prepare food, to irrigate crops and for recreation, pose a major threat to human health when contaminated.


About 3.4 million people die each year from diseases associated with pathogens in water, like cholera, typhoid, infectious hepatitis, polio, ascariasis (roundworm infection) and diarrhoeal diseases. Many of these diseases are due to the presence of human waste in water.

UN Environment estimates that up to 25 million people are at risk of infection from these diseases in Latin America, up to 164 million in Africa and up to 134 million in Asia. The solution is not only to build more sewers but to treat wastewater.

Organic pollution

Severe organic pollution, which is caused when large amounts of decomposable organic compounds are released into water bodies, now affects around one out of every seven kilometres of all river stretches in Latin America, Africa and Asia. This type of pollution can lead to the complete deoxygenation of water bodies, posing a major threat to freshwater fisheries that provide humans with the sixth most important source of animal protein and, in developing countries, employ 21 million fishermen and create 38.5 million related jobs.


Severe and moderate salinity pollution already affects around one-tenth of all river stretches in Latin America, Africa and Asia. High salinity levels, which occur when humans dump salty wastewater from mines, irrigation systems and homes into rivers and lakes, make it even harder for the world’s poorest farmers to irrigate their crops. Salinity pollution has increased between 1990 and 2010 in almost one-third of all rivers in the three continents.


Agriculture has intensified and expanded as the world seeks to meet the growing food demands of a booming population. This has led to an increase in the amount of phosphorus from fertilisers and pesticides that pollute waterbodies. The resulting eutrophication can lead to a boom in nuisance plants and algal blooms, as well as changes in ecosystem structure and fish species.

More than half of the total phosphorus loads in 23 out of 25 major lakes worldwide are from human sources – inorganic fertiliser, livestock waste, human sewage. Most of the major lakes in Latin America and Africa now have higher levels of phosphorus than in 1990.

India-Case study of the Godavari basin

In the case of India, commenting on the Godavari basin and the pollution levels, the pre-study has noted that the river-the 2nd longest in India with the 3rd largest basin, and a catchment area of 312,812 km of agricultural land and forests, suffers due to severe organic pollution. Low average annual rainfall has severely affected the discharge in this river, which has four important tributaries- the Manjira, Pranhita, Indravati and the Sabari.


The population density in the basin ranges from 25–50 persons/sqkm to 500–1,000 persons/sqkm. More than 441 towns, 58,072 settlements and 33 cities are located in the basin. Around 75 per cent of the total population of 60.57 million in the basin are rural, with the other 25 per cent in urban areas.

Using data from several monitoring stations along the river, it notes that the water quality of the Godavari does not meet the required criteria for Class A – “Drinking Water Source without conventional treatment but after disinfection”, including for the parameter biochemical oxygen demand (BOD). Figure 2 summarises the long term trend of BOD from several monitoring stations in the river (UNEP Report). While there is a variation in the peaks, mean BOD levels are more or less constant.

The Report has blamed discharge of untreated and partially treated sewage from cities as one of the principal reasons for non-compliance of water standards. The sources of water pollution – as per the report are-

  • domestic sewage
  • industrial effluent,
  • agricultural non-point sources.

In the absence of any effluent advisory, assuming the generation of approximately 80 litres of sewage per person in urban areas and approximately 50 litres sewage in rural regions, the report assumes the volume of raw sewage entering Godavari as approximately 3,000 million litres per day. Further assuming an average BOD concentration of 200 mg/litres and an average treatment capacity of 40 per cent, the total BOD load is estimated at 219,000 t/yr. This corresponds to an average BOD intensity of 409 kg/km/day of river length. Noting the high number of sugar and distillery units in Andhra Pradesh (which is situated in the lower Godavari basin), as also the pulp and fertiliser companies which are large consumers of water, the report blames these for the deterioration in water quality from Nashik and Nanded in Maharashtra to Bastar in Chhattisgarh and Burgampahad in Andhra Pradesh, as cited by the Central Pollution Control Board.

Solutions to the water quality challenge

Pointing out that there is still time to tackle water pollution, the Report calls for better water monitoring, especially in developing countries to understand the scale of the challenge and to identify key hotspots. Once in-depth assessments have been done there are a large number of new and old methods, it notes, that can help to reduce the pollution at source, treat polluted water before it enters water-bodies, recycle wastewater for irrigation and protect ecosystems by, for example, restoring wetlands to remove pollutants from urban or agricultural run-off.

In the case of the Godavari, noting the inadequacy of the water quality index (WQI) used by the Central Pollution Control Board, the report recommends the location importance index( LII) that was developed for use. It recommends using the data from the existing monitoring stations to identify pollution-related stress in the waters. Recommending the setting up of automated monitoring in the worst–polluted stretches, it notes the need for comprehensive impact assessment which goes beyond the assessment of in-stream water quality to cover the entire river basin ecosystem. In short, the report calls for a holistic impact assessment, using parameters such as water use (domestic, industrial agricultural) non-point pollution loads, agricultural yield, public health indicators,groundwater quality, ground water levels, biodiversity,top soil contamination and climate change related vulnerability.


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