Biological Wastewater Treatment

1. Biological Wastewater Treatment Plants

Biological wastewater treatment utilizes active microorganisms to digest, metabolize, and degrade organic contaminants, effectively reducing Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), and Ammoniacal Nitrogen. Water Lanka Services designs and constructs world-class biological treatment facilities engineered for Sri Lankan climatic conditions and diverse industrial effluents.

Anaerobic Treatment Plants: High-rate anaerobic digestion systems, Upflow Anaerobic Sludge Blanket (UASB) reactors, and anaerobic baffled reactors designed to treat high-strength organic wastewater (BOD > 2,000 mg/L) from food processing, breweries, distilleries, and dairy industries with minimal sludge generation and optional biogas capture.
Aerobic Treatment Plants: High-efficiency Activated Sludge Plants (ASP), Extended Aeration systems, Moving Bed Biofilm Reactors (MBBR), and Sequencing Batch Reactors (SBR) delivering over 95% BOD and COD reduction for textile, chemical, hotel, and institutional facilities.
Construction of Aeration Tanks: Comprehensive civil engineering and reinforced cement concrete (RCC) construction of deep aeration tanks, equalization basins, and clarifier tanks. We integrate heavy-duty fine bubble membrane disc/tubular diffusers, Roots blowers, jet aerators, and stainless steel air headers for optimal oxygen transfer efficiency (OTE).
Facultative Ponds & Stabilization Lagoons: Cost-effective biological treatment ponds designed for agricultural processing, livestock farms, rubber and palm processing, and large industrial facilities with sufficient land area. Utilizing natural symbiosis between aerobic bacteria and algae in upper layers and anaerobic digestion at the base.

Chemical Water Treatment and pH Correction Systems Sri Lanka

Chemical Treatment Systems

2. Chemical Water & Wastewater Treatment Plants

Chemical water treatment is essential for destabilizing colloidal particles, removing dissolved heavy metals, precipitating phosphates, breaking chemical emulsions, and neutralizing extreme acidity or alkalinity. Water Lanka Services designs custom automated chemical dosing skids and flash mixing/flocculation reactors.

Coagulants & Rapid Mixing: Precision dosing of primary coagulants including Polyaluminium Chloride (PAC 30%), Alum (Aluminium Sulphate), Ferric Chloride, and Ferrous Sulphate to neutralize negative zeta potential charges on suspended particles.
Flocculants & Floc Formation: Preparation and dosing systems for Anionic Polyacrylamide (APAM) and Cationic Polyacrylamide (CPAM) high-molecular-weight polymers, accelerating bridge formation and creating dense, rapid-settling flocs.
pH Adjusters & pH Boosters: Dosing systems for Caustic Soda (NaOH), Hydrated Lime (Ca(OH)2), and Soda Ash (Na2CO3) to boost pH in acidic effluents (e.g., anodizing, rubber latex, electroplating, chemical processing).
Automated pH Correction Systems: Fully integrated closed-loop pH correction skids featuring dual-chamber neutralization tanks, digital inline pH sensors, heavy-duty mixers, and proportional metering dosing pumps with PLC/scada controls to guarantee treated effluent stays strictly within CEA's 6.0 - 8.5 pH discharge window.

Physical Water Treatment

3. Physical Water Treatment & Filtration Plants

Physical water treatment relies on mechanical separation forces—gravity sedimentation, flotation, centrifugal vortexing, and barrier filtration—to capture suspended solids, grit, free oils, and particulate matter without altering chemical composition.

Preliminary Mechanical Screening: Heavy-duty stainless steel coarse bar screens, mechanical rotary drum fine screens (0.5mm - 2mm), and basket strainers for lint and debris removal in textile and municipal wastewater.
Oil & Grease Separation: API gravity separators, parallel corrugated plate interceptors (CPI), and high-efficiency Dissolved Air Flotation (DAF) units for restaurants, service stations, food factories, and edible oil plants.
Sedimentation & Clarification: Lamella inclined plate clarifiers and secondary circular clarifiers with motorized central sludge scrapers for rapid liquid-solid settling.
Advanced Pressure Filtration Plants: Pressure sand filters (PSF), multimedia filters (dual media anthracite & sand), activated carbon filters (ACF), and multi-cartridge stainless steel polishers delivering crystal-clear water with turbidity < 1 NTU.

Turnkey Industrial Plant Construction Capabilities in Sri Lanka

Water Lanka Services (Pvt) Ltd provides end-to-end EPC (Engineering, Procurement, Construction) solutions for new wastewater treatment plants, capacity expansions, and system retrofits throughout Sri Lanka, including Colombo, Gampaha, Katunayake, Biyagama, Kandy, Kurunegala, Galle, and Jaffna industrial zones:

1. Engineering & Design

Effluent characterization, mass-balance calculations, P&ID schematics, hydraulic profile, and Central Environmental Authority (CEA) Environmental Protection License (EPL) submission drawings.

2. Civil RCC Construction

On-site excavation, shuttering, reinforced concrete civil construction of aeration tanks, equalization tanks, settling clarifiers, sludge drying beds, and pump dry/wet wells with waterproof crystalline coating.

3. Mechanical & Electrical

Installation of submersible sewage pumps, Roots air blowers, jet aerators, fine bubble diffusers, chemical dosing pumps, filter presses, electrical MCC control panels, and automated PLC control systems.

4. Commissioning & Handover

Bacterial seeding and microbial bio-culture cultivation, chemical dosage jar testing, trial runs, operator training, and final laboratory discharge compliance testing for CEA EPL approval.

Wastewater Treatment Method Comparison

Treatment Stage	Process Technology	Target Pollutants Removed	Typical Removal Efficiency	Ideal Industrial Applications
Physical Treatment	Bar Screens, Grit Traps, DAF, Sand/Carbon Filters	TSS, Floating Oil/Grease, Silt, Coarse Fibers	80% - 95% TSS, 90% Oil & Grease	Textile, Automobile Service Stations, Food & Meat, Pre-treatment
Chemical Treatment	Coagulation (PAC/Alum), Flocculation (PAM), pH Correction	Colloidal Solids, Heavy Metals, Phosphates, pH Inbalance	85% - 98% Colloids, 99% Metal Precipitation	Electroplating, Chemical, Textile Dyeing, Paint & Pigment
Biological Aerobic	Aeration Tanks, SBR, MBBR, Activated Sludge	Dissolved Organics (BOD, COD), Ammonia Nitrogen	90% - 98% BOD5, 85% - 95% COD	Hotels, Apartments, Hospitals, Breweries, Commercial Buildings
Biological Anaerobic	UASB Reactors, Anaerobic Digestion Tanks, Baffled Reactors	High-strength COD/BOD (>2,000 mg/L), Sludge Degradation	75% - 88% COD, Biogas Energy Recovery	Distilleries, Sugar Mills, Starch & Agro-processing, Dairy
Natural Biological	Facultative Ponds, Maturation & Polishing Lagoons	Pathogens, Coliforms, Residual Nutrients (N, P)	99% Coliform Reduction, Low OPEX	Rubber Estates, Palm Oil Mills, Rural Municipal Waste, Large Acreage

What is the difference between anaerobic and aerobic wastewater treatment?

Anaerobic treatment takes place in the absence of dissolved oxygen, utilizing anaerobic bacteria to convert high-strength organic waste into methane gas and carbon dioxide with minimal electrical energy and low sludge yield. Aerobic treatment requires continuous oxygen bubbling via aeration tanks and Roots blowers to stimulate aerobic bacteria for rapid polishing of BOD and COD to meet inland water discharge limits.

Can Water Lanka construct aeration tanks on-site in Sri Lanka?

Yes. Water Lanka Services provides complete reinforced concrete (RCC) civil construction of aeration tanks, equalization basins, settling clarifiers, and pump wells across Sri Lanka, including custom dimensions, water-retaining waterproofing concrete, epoxy coating, and diffuser pipe installations.

Why is pH correction crucial for industrial effluent in Sri Lanka?

The Central Environmental Authority (CEA) of Sri Lanka mandates that industrial wastewater discharged into inland surface waters or public sewers must strictly maintain a pH between 6.0 and 8.5. Water Lanka provides automated dual-action pH adjusters and boosters (Caustic Soda, Hydrated Lime, and Acid dosing skids) with digital online pH sensors to maintain compliant discharge 24/7.

Biological, Chemical & Physical Wastewater Treatment Plant Construction in Sri Lanka