Action Programs
in Sri Lanka

Groundwater Monitoring for Industrial Effluent Management in Sri Lanka

Background and objective

In Sri Lanka, industries are categorised into three broad groups, namely Type A, B and C by the Central Environment Authority (CEA) depending upon the severity of their pollution potential and to guide the siting of such industries. According to the data, a total of 11,449 high polluting industry units (Type A) and 10,711 medium polluting industrial units (Type B) operate within Sri Lanka. It is mandated by law that effluents from industry be treated according to the designated national effluent standards prior to discharge; however, the rise in industry density, lack of firm commitments and loopholes in regulations have together led to an increase in the prevalence of industry-related pollution issues of late, chief of which is groundwater table pollution. The WEPA Action Program in Sri Lanka was launched in Gampaha District to evaluate wastewater pollution control strategies and sludge disposal methods in order to prevent groundwater pollution.


The Action Program evaluated wastewater management in 13 Type A industries and conducted water quality surveys in wastewater treatment facilities and 96 groundwater wells in the vicinity of selected industries. Data loggers were also installed in 13 reference wells to monitor water depth and temperature. Five rounds of surveys were conducted during 2017 and 2018 for all 96 wells to cover all four major seasons. The project also involved dispatching groundwater experts from Japan to provide on-site technical advice on program implementation. Wastewater treatment and sludge management systems for all 13 investigated industries were reviewed, which revealed that wastewater treatment systems are generally constructed in-house for the majority of industries. However, the level of treatment they offer is still very basic and at the primary level, mainly consisting of a settling tank, sand filter, aeration chamber and maturation tank. Some industries were in the process of upgrading treatment facilities such as through introducing ion exchange, ozonation or other tertiary treatments. For sludge, some industries still rely on off -site management facilities, while others are seeking environmentally and economically efficient solutions through using sludge materials as inputs to other by-product stage industrial processes.


Figure 1 shows a map of the investigated industries together with the COD concentrations in groundwater at various distances from the respective industries. From the multi-season survey on groundwater wells, it was found that the majority of water quality parameters did not exceed tolerance limits set by CEA for the majority of the samples. For COD, only one well which was 63 meters from industries A & B on the map exceeded the 50 mg/L tolerance limit value for outfalls leading up to nearshore water. While no strong correlation between concentration and distance from wells was found, groundwater close to certain industries such as A & B showed significantly higher levels of COD compared to others. being processed. Parameters such as Pb, Cr, Cu, Fe, and phosphate were mostly below instrument detection limits. Further analysis is required to consider other parameters which may affect the data, such as depth of the surveyed well/aquifer, baseline groundwater quality, other pollution sources, quality of the actual industrial effluent discharged, or statistical analysis of daily/temporal fluctuations

Figure 1. Map of investigated industries and COD concentrations of groundwater at different distances from the investigated industries (The industries are labelled from A to M for convenience of this report. Each dot in the scatterplot represents the mean value of COD analysed up to 5 times at different seasons in the same well).

Conclusions and recommendations

  • Further analysis on the raw industrial wastewater in addition to other potential pollution sources should be conducted to determine contamination pathways, especially for wells near industries A & B. Based on the contamination pathways identified, potential solutions can be investigated as the next step.
  • The observed parameters could be used as a benchmark to assess any future changes or deterioration in groundwater quality in the area. The data obtained from the Action Program as well as follow-up monitoring could prove valuable in assessing future impact on groundwater due to the likely rise in industrial activity in this area, including that of small and medium enterprises which are not well regulated at present.
  • Certain industries, especially the larger ones that generate high volumes of wastewater, could consider improving their wastewater treatment to add tertiary treatment and appropriate sludge management practice, to avoid pollution of groundwater and surface water compared to the relatively unaffected current state. With a view that this will be beneficial to the local communities which utilise these water sources, financial instruments such as subsidies from the national or local government to these practices could be considered.
  • Proper policies and regulations for zonation should be made effective and consideration should be given for areas where groundwater usage is common. Also, the siting of highly polluting industries as well as disposal options should be thoroughly scrutinised.
  • Identification of general hydrology and hydrogeology of areas intended for industries and design of appropriate effluent discharge systems in accordance therewith should be considered.


Report of WEPA Action Program in 2019 (3.3 Mbite)