Maintaining low turbidity is one of the most important goals in wastewater treatment, especially as Nepal strengthens its environmental regulations and urban populations grow. High turbidity not only affects the clarity of water but also reduces treatment efficiency, increases chemical consumption, and makes disinfection far less effective.
As industries and municipalities upgrade treatment plants across Nepal, understanding what causes turbidity and how to remove it efficiently is essential for compliance and sustainable operations.
What Is Turbidity and Why Does It Matter?
Turbidity of water refers to how cloudy or hazy it appears due to suspended solids, colloidal particles, microorganisms, or organic matter. Clear water has low turbidity, while cloudy or coloured water has high turbidity.
High turbidity impacts treatment in multiple ways:
- Makes sedimentation and filtration less effective
- Protects pathogens from disinfectants
- Increases chlorine demand
- Leads to poor treated-water quality
- Reduces reuse potential
For wastewater plants, controlling turbidity is fundamental to achieving safe discharge standards and maintaining stable plant performance.
Turbidity Is Mainly Due To…
Various industrial, municipal, and natural factors contribute to high turbidity in Nepal’s wastewater streams. Turbidity is mainly due to:
1. Suspended Solids
Clay, silt, grit, and organic particles from domestic sewage and stormwater.
2. Industrial Pollutants
Fibres, dyes, latex, chemicals, and solids from industries such as:
- Textile
- Paper & pulp
- Leather
- Food processing
- Metal finishing
3. Microbial Growth & Algae
In untreated or poorly maintained lagoons, algae and bacteria significantly increase water cloudiness.
4. Colloidal Matter
Fine particles that do not settle easily require chemical treatment to coagulate.
5. Oil & Grease
Especially from food industries, workshops, and mechanical plants, which form emulsified layers that increase turbidity.
These factors make turbidity one of the most important parameters monitored using a turbidity meter in modern treatment plants.
Measuring Turbidity: Why It Matters?
A turbidity meter provides real-time insights into plant performance. Continuous monitoring helps:
- Optimise chemical dosing
- Detect upsets early
- Maintain consistent effluent quality.
- Ensure effective filtration and disinfection.
- Support regulatory compliance
In Nepal, accurate turbidity monitoring has become increasingly important as more plants aim to reuse treated water or safely discharge into rivers.
How to Reduce Turbidity in Wastewater Treatment?
Effective control requires a combination of mechanical, chemical, and biological processes. Modern wastewater systems designed for Nepal typically include:
1. Coagulation & Flocculation
Coagulants destabilise fine particles, while flocculants bind them together into settleable flocs. This is the most crucial step in turbidity reduction.
2. Clarification (Primary & Secondary)
Lamella clarifiers, circular clarifiers, or DAF units remove suspended solids efficiently.
3. Biological Treatment
MBBR, activated sludge, or MBR processes reduce organic load, lowering turbidity caused by microbial and organic matter.
4. Filtration Systems
- Pressure sand filters
- Activated carbon filters
- Ultrafiltration (UF) membranes
These remove remaining suspended particles and ensure stable effluent clarity.
5. Disinfection
Chlorine, UV, or ozone work effectively only when turbidity is low. Good control ensures disinfection efficiency and compliance.
6. Sludge Management
Regular desludging prevents solids build-up, a common cause of fluctuating turbidity in Nepalese treatment plants.
Why Turbidity Control Is Crucial for Drinking Water?
While this blog focuses on wastewater, turbidity also directly impacts the turbidity of drinking water. High turbidity can:
- Shield pathogens like bacteria and protozoa
- Reduce chlorine effectiveness
- Affect taste and appearance.
- Lead to regulatory violations.
For both wastewater and drinking water systems, maintaining low turbidity is essential for protecting public health.
Ion Exchange’s Expertise in Turbidity Reduction
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 mudball 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 23,0, 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
Floc formation and settling in the reaction chamber. Fish swimming in the Settling Tank. 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.
Conclusion
High turbidity is one of the most common and challenging issues in Nepal’s wastewater treatment plants. By understanding its causes and implementing advanced treatment technologies, facilities can achieve stable plant operation, meet discharge norms, and move toward sustainable reuse.
Connect with Ion Exchange experts to explore customised turbidity-control solutions designed for wastewater treatment plants across Nepal.