In Sri Lanka, ensuring access to clean, safe, and clear water is not only a public health priority but also a critical part of environmental protection and industrial development. Whether it’s for drinking water, food processing, or pharmaceutical production, the clarity of water plays a crucial role in defining its quality. One of the most reliable indicators of clarity — and thus quality — is turbidity.
Monitoring the turbidity of water helps identify the presence of suspended particles, sediment, and organic matter that affect both the appearance and safety of water. By understanding and controlling turbidity, water treatment plants across Sri Lanka can guarantee that every drop delivered to communities meets international standards for purity.
What is Turbidity?
Turbidity is a measure of how clear or cloudy water appears due to suspended particles such as clay, silt, microorganisms, and organic matter. When light passes through water, these particles scatter and absorb it — the more scattering, the higher the turbidity.
High turbidity not only affects water’s appearance but also indicates the potential presence of contaminants. Turbid water can shield harmful microorganisms from disinfection processes, making proper monitoring vital for ensuring safe drinking water.
Turbidity of Water Unit and Measurement
The turbidity of water is expressed as Nephelometric Turbidity Units (NTU). Turbidity meters, or nephelometers, measure the intensity of light scattered at a 90-degree angle as it passes through a water sample.
Typical turbidity ranges include:
- 0–1 NTU: Excellent clarity — standard for drinking water.
- 1–5 NTU: Acceptable for most industrial and municipal uses.
- >5 NTU: Indicates contamination or insufficient filtration.
In Sri Lanka, regulatory bodies and utilities follow World Health Organization (WHO) and Sri Lanka Standards Institution (SLSI) guidelines, which specify that drinking water should have turbidity levels below 1 NTU for optimal safety and aesthetics.
Even the turbidity of distilled water — which should ideally read 0 NTU — is periodically measured in laboratories and pharmaceutical facilities to verify system purity and instrument calibration.
Why Turbidity Monitoring Matters?
Monitoring turbidity helps ensure:
- Effective Filtration: Detects inefficiencies in filters, membranes, and clarifiers.
- Reliable Disinfection: High turbidity can reduce chlorine or UV disinfection efficiency.
- Regulatory Compliance: Ensures treated water meets national and WHO drinking water standards.
- Operational Efficiency: Real-time monitoring allows for quick corrective actions, preventing large-scale contamination.
In regions like Sri Lanka, where water sources often experience seasonal variations, turbidity levels can rise sharply after monsoon rains due to sediment runoff. Continuous monitoring helps operators adjust coagulant dosing, filter backwashing, and treatment processes in real-time.
Ion Exchange’s Expertise in Turbidity and Water Quality Management
Enhancing Water Quality at Lucknow Water Treatment Plant
The Water Treatment Plant in Lucknow, Uttar Pradesh, with a capacity of 200 MLD, plays a crucial role in supplying drinking water to over 1 million residents. However, the plant faced significant challenges due to its British-era infrastructure, particularly conventional settling tanks (70m x 70m x 3.0m) that had minimal clarification zones, leading to frequent mud carryover and poor water quality. Additionally, issues such as mud ball formation in filters, high chemical consumption, excessive sludge generation, and manual alum dosing created inefficiencies in the treatment process.
To address these challenges, Ion Exchange India Limited (IEIL) implemented an advanced polymer dosing system using Polyaluminium Chloride (PAC 2000 MT), INDFLOC 230, and INDFLOC 27. This optimized treatment approach improved coagulation and flocculation, significantly enhancing water clarity. As a result, the plant achieved turbidity levels of <1.0 NTU at the tap, eliminated excessive sludge generation, and reduced material handling costs by saving approximately 8-12 tonnes per day of PAC. Additionally, on-site erection of a 200 MLD dosing facility ensured consistent treatment and long-term operational efficiency. The success of this intervention was evident as the treatment became non-toxic, with fish observed in settling tanks, indicating improved water quality.
Water Quality Improvement at Varanasi Water Treatment Plant
The Varanasi Water Treatment Plant, with a capacity of 250 MLD, serves as a vital drinking water source for the city. However, the plant’s outdated infrastructure, including conventional settling tanks, led to high sludge generation, poor treated water quality during rainy seasons, and elevated colour levels that exceeded drinking water standards. Additionally, manual tank cleaning and frequent mud carryover further deteriorated water clarity, making it essential to modernize the treatment process.
To overcome these issues, Ion Exchange India Limited (IEIL) introduced a dual-polymer dosing system, optimizing the coagulation and flocculation processes. The treatment incorporated INDFLOC 238 as the primary coagulant in combination with PAC, while INDFLOC 27 was used as a flocculant to enhance particle removal. These improvements led to a significant reduction in colour and turbidity, ensuring year-round compliance with drinking water standards, even during the rainy season. Additionally, the dosing system was upgraded to handle 450 MLD, preparing the plant for future demand while reducing operational costs and chemical consumption. This transformation resulted in consistently safe and high-quality drinking water for the city.
The Road to Clear Water Standards in Sri Lanka
As Sri Lanka continues investing in infrastructure under its National Water Supply and Drainage Board (NWSDB) initiatives, maintaining low turbidity levels is central to delivering safe and reliable drinking water. Through advanced sensors, automated reporting, and smart plant integration, the country’s water sector is adopting technologies that make real-time water quality control a reality.
Ion Exchange’s modern treatment systems and continuous monitoring tools play a key role in this transformation — ensuring that Sri Lanka achieves international standards for clean, clear, and safe water for all.
Conclusion
Turbidity may seem like a small parameter, but it serves as one of the most important indicators of water quality. Monitoring the turbidity of water ensures effective filtration, reliable disinfection, and compliance with health standards. Even the turbidity of distilled water in laboratories and high-purity systems reflects the precision required in today’s water management.
With Ion Exchange’s innovative water treatment and monitoring technologies, utilities and industries in Sri Lanka can ensure transparency — both in water quality and operational performance.
