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The Vulcan Sewage Treatment Plant (STP), developed by SKF Elixer India Pvt. Ltd., is a prefabricated, pre-engineered wastewater treatment system powered by Advanced Attached Growth Bioreactor (AABR) technology. Designed for compact, efficient, and low-maintenance operation, it treats sewage from residential complexes, hotel, hospitals, and industrial factories with capacities ranging from 5 to 100 KLD (thousands of liters per day). The stainless-steel construction ensures durability (15-20 years lifespan), minimal footprint (as low as 5-10 sq. meters for 50 KLD), and compliance with CPCB standards (e.g., BOD <30 mg/L).
This system transforms raw sewage—characterized by high BOD (250-300 mg/L), COD (450-550 mg/L), and nutrients—into clear, reusable water suitable for non-potable uses like gardening, flushing, cooling, or floor cleaning. It achieves 85-90% reduction in BOD and COD, generates low sludge (50-100 kg/month for 50 KLD), and operates with low power (50-100 kW/month for 50 KLD) and no skilled operators required.
This article covers the step-by-step breakdown of the STP working process and key advantages of installing AABR STP technology for organisation and interprises.
What is Synthetic Media in Wastewater Treatment
Synthetic media, often used in biofilm-based systems like AABR (and commonly associated with Moving Bed Biofilm Reactor, MBBR, systems), consists of lightweight, durable plastic carriers that provide a surface for microorganisms to grow and form a biofilm. This biofilm degrades organic matter and pollutants, making it a cornerstone of efficient sewage treatment plants.
SKF Elixer’s AABR technology uses specially designed synthetic media to optimize wastewater treatment.
Biological STP Treatment Process Breakdown
1. Screening (Bar Screen Chamber)
The screening stage in the Vulcan STP AABR plant, specifically the bar screen chamber, serves the primary purpose of removing large floating solids and debris to protect downstream equipment from clogging and damage.
It utilizes a stainless-steel bar screen with fine mesh, typically featuring 6-10 mm gaps. In this process, raw sewage enters the plant and passes through the bar screen, where coarse materials such as plastics, rags, and food scraps—amounting to 50-100 kg/day for a 100 KLD capacity—are trapped and manually or automatically removed for disposal, thereby preventing blockages in pumps and pipes. Key parameters include handling peak flows up to 20% above average with a retention time of 5-10 minutes.
Unique features encompass its integration into the prefab unit, requiring no civil work and reducing setup time to 2-4 weeks. Overall, this stage achieves an efficiency of removing 70-80% of gross solids, which lowers the organic load for subsequent stages.
2. Oil and Grease Separation (Oil & Grease Trap)
The oil and grease separation stage, known as the oil and grease trap, aims to skim off floating oils, fats, and greases to reduce interference with biological treatment.
It employs a gravity-based oil and grease trap equipped with a skimmer mechanism. During the process, sewage flows into a baffled chamber where lighter oils and fats rise to the surface due to density differences, allowing a skimmer to collect and remove them particularly common in kitchen or industrial effluents while heavier solids settle at the bottom for periodic sludge removal, with treated effluent overflowing to the next stage.
Key parameters involve a retention time of 15-30 minutes and removal of 80-90% of free oils. Unique features include corrosion-resistant stainless-steel construction that prevents rust, along with minimal maintenance as skimmings are collected weekly.
This stage efficiently reduces FOG (fats, oils, grease) levels from 50-100 mg/L to less than 10 mg/L, thereby enhancing AABR performance.
3. Equalisation (Equalisation Tank)
The equalisation stage, utilizing the equalisation tank, balances fluctuations in sewage flow and pollutant concentration to ensure stable downstream treatment.
It features an aerated equalisation tank with mixers or diffusers. In this process, inconsistent inflows, such as those from peak usage in apartments, are collected here, where aeration or mechanical mixing homogenizes the sewage to prevent septic conditions and ensure uniform BOD/COD levels, with excess volume stored for gradual release via pumps. Key parameters include a hydraulic retention time (HRT) of 4-8 hours and a volume equivalent to 20-30% of daily capacity, such as 10-30 m³ for 50 KLD.
Unique features comprise low-energy aeration at 0.5-1 kWh/m³ and auto-level sensors for overflow prevention. The efficiency of this stage stabilizes pH between 6.5-8 and reduces shock loads by 10-20%, ensuring consistent AABR operation.
4. Biological Treatment (AABR Chamber)
The biological treatment stage, centered on the AABR chamber, focuses on the core degradation of organic matter and nutrients using attached-growth biofilm.
It incorporates an AABR (Attached Growth Bio-Reactor) chamber filled with advanced synthetic fiber media that is UV-resistant and offers high surface area. The process involves pre-treated sewage entering the baffled reactor, where microorganisms colonize the synthetic media to form a biofilm, creating anaerobic and aerobic zones that break down organics through hydrolysis, acidogenesis, and methanogenesis to reduce BOD/COD, while nutrients like nitrogen and phosphorus are assimilated or denitrified, with no constant aeration needed as natural flow promotes biomass growth.
Key parameters encompass an HRT of 12-24 hours, media surface area of 200-300 m²/m³, and sludge yield of 0.2-0.4 kg/kg BOD removed. Unique features include faster biomass growth leading to stabilization in weeks rather than months, non-clogging media that lasts 15-20 years, and the ability to handle load variations without breakdowns. Efficiency is marked by 70-80% BOD/COD removal and low sludge generation due to the fixed biofilm.
5. Primary Settling (Settling Tank after AABR)
The primary settling stage, involving the settling tank after AABR, separates biomass and settled solids from the biologically treated effluent. It uses a primary settling tank that is conical or rectangular in stainless-steel design.
In the process, effluent from the AABR flows in, allowing heavier sludge particles to settle by gravity, with clarified water overflowing to the next stage and settled sludge periodically pumped out, such as monthly, to drying beds. Key parameters include a surface loading rate of 20-40 m³/m²/day and settling time of 1-2 hours. Unique features consist of an integrated sludge recirculation option to maintain AABR biomass and minimal operator intervention. This stage efficiently removes 50-70% of suspended solids (TSS), producing clearer water with TSS under 100 mg/L.
6. Sludge Handling (Drying Beds)
The sludge handling stage, employing drying beds, dewaters and stabilizes sludge for safe disposal or reuse. It features sludge drying beds made of sand or gravel, or alternatively a mechanical dewatering unit. The process entails pumping sludge from settling tanks here, spreading it thinly on permeable beds, and allowing it to dry via evaporation and drainage, with solar drying taking 7-14 days to reduce volume by 80-90%, after which dried sludge can be used as fertilizer or disposed. Key parameters involve a loading rate of 100-200 kg/m²/year and moisture reduction from 98% to 20-30%.
Unique features include an eco-friendly, low-cost drying method that aligns with the system’s minimal sludge output of 50-100 kg/month for 50 KLD. Efficiency results in producing stable, odor-free sludge compliant with disposal norms.
7. Secondary Settling/Clarification (Secondary Settling Tank)
The secondary settling or clarification stage, utilizing the secondary settling tank, further clarifies water by removing any remaining fine solids. It incorporates a secondary settling tank (SST) with clarifiers. In the process, partially treated water undergoes additional gravity settling to capture flocculated particles, with overflow collected as clarified water and underflow sludge returned to drying beds. Key parameters include an HRT of 30-60 minutes and an overflow rate of 1-2 m³/m²/hour.
Unique features encompass stainless-steel construction that prevents corrosion and automated sludge withdrawal. This stage efficiently reduces TSS to less than 50 mg/L, preparing water for filtration.
8. Clarified Water Collection (Clarified Water Tank - CWT)
The clarified water collection stage, involving the clarified water tank or CWT, stores and buffers clarified effluent before final polishing. It uses a clarified water tank as the main equipment.
The process includes storing settled water here to allow any residual settling, with pH adjustment if needed and flow metering occurring before transfer to filters. Key parameters consist of a storage volume of 10-20% of daily flow and monitoring for dissolved oxygen greater than 2 mg/L.
Unique features include integrated sensors for real-time quality checks and no odor due to aerobic conditions. Efficiency ensures steady flow to filters, maintaining overall system stability.
9. Tertiary Filtration - Sand Filter
The tertiary filtration stage, focused on the sand filter, removes fine suspended solids and turbidity for crystal-clear water. It employs a sand filter that is multi-media or a single sand bed.
In the process, clarified water passes downward through layered media such as sand, gravel, and anthracite, trapping particles via adsorption and straining, with backwashing every 24-48 hours to clean the bed using treated water. Key parameters include a filtration rate of 5-10 m³/m²/hour and backwash frequency of 2-4 times per week.
Unique features comprise automatic backwash valves and contributions to 30-50% water recycling. Efficiency reduces turbidity to less than 5 NTU and TSS to less than 20 mg/L.
10. Final Polishing and Disinfection
The final polishing and disinfection stage, utilizing the polishing filter and hypochlorite dosing, eliminates residual organics, pathogens, and odors for reuse-ready water.
It features an activated carbon polishing filter combined with a hypochlorite dosing pump. The process involves water flowing through the polishing filter to adsorb dissolved organics and colors, followed by chlorine dosing at 5-10 ppm for disinfection to kill bacteria and viruses, with a contact time of 20-30 minutes in a storage tank.
Key parameters include chlorine residual of 0.5-1 mg/L and contact time of 30 minutes. Unique features encompass odor-free output and automated, minimal dosing with no daily chemicals except for disinfection. Efficiency achieves zero coliforms, final BOD less than 10 mg/L, and COD less than 50 mg/L.
Advantages of Synthetic Media in STP Systems
Vulcan STP is fully prefabricated and pre-engineered, embodying “less is more” in wastewater management. The Attached Growth Bioreactor (AABR) integrates with Advanced Design Variants (ADV) for a holistic, low-impact system.
Key highlights include:
- Less Footprint Area: Up to 70% smaller than conventional STPs, freeing up valuable space.
- Minimal Operator Work (Auto Work): Automation handles pH balancing (6.5-8 to 7-8) and dosing, requiring just basic monitoring.
- SS Long Life of Units: Corrosion-resistant stainless steel ensures 20+ years of durability, with no rust or leaks.
- Nitrogen Treatment: Effectively removes nitrogen and phosphorus, preventing eutrophication in discharge waters.
- No Smell/Odour: Fully aerobic operation with positive dissolved oxygen and vented covers eliminates foul odors entirely.
- Quick Maintenance & Low OPEX: No moving parts mean fewer breakdowns; sludge drying beds handle dewatering efficiently.
- Low Sludge Generation: Minimal biological sludge reduces disposal costs and environmental footprint.
- Just-in-Time Investment: Stocked modules allow phased rollout, optimizing capital expenditure.
- Can Be Relocated: Portable design supports business mobility or site changes.
- High Efficiency: The large surface area of plastic biofilm media enhances microbial activity, achieving 90–95% pollutant removal, compared to 70–80% in conventional systems.
- Low Energy Use: AABR systems consume 30–40% less power, saving ₹1–2 lakh annually for a 100 KLD plant, critical for power-scarce rural areas.
- Compact Design: Synthetic media allows for smaller reactor sizes, reducing land requirements by 50%. A 50 KLD plant needs only 20–30 square meters, ideal for space-constrained places.
- Durability: Media withstands harsh conditions, lasting 10–15 years, reducing replacement costs by ₹2–3 lakh over the system’s lifespan.
SKF Elixer’s Solutions for Diverse Applications
SKF Elixer’s AABR-based STPs, enhanced by synthetic media, cater to municipal, industrial, and rural needs across India.
Conclusion
Synthetic media is revolutionizing wastewater treatment, offering efficient, sustainable, and cost-effective solutions for India’s urban and rural landscapes. SKF Elixer’s AABR-based STPs, powered by advanced biofilm media, deliver high-quality treatment while addressing economic and environmental needs.
By adopting our systems, communities and industries can transform wastewater management into a cornerstone of sustainability. Ready to embrace sustainable wastewater treatment? Contact SKF Elixer to explore our tailored STP solutions and drive a cleaner tomorrow.
FAQs
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How does synthetic media improve sewage treatment efficiency?
Synthetic media in our AABR systems provides a high surface area for biofilm growth, achieving 90–95% BOD and COD reduction. This enhances treatment efficiency, saving ₹1–2 lakh annually in energy costs for a 50 KLD plant compared to traditional systems.
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What are the advantages of synthetic media in ETP plants for industries?
In industrial effluent treatment, synthetic media handles high organic loads, achieving 95% COD reduction. For a 200 KLD plant, this ensures compliance with CPCB norms, saving ₹5–10 lakh annually in fines and enabling water reuse, ideal for industries.
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What role does plastic biofilm media play in STPs?
Plastic biofilm media fosters microbial growth, degrading pollutants efficiently. It reduces reactor size by 50%, lasts 10–15 years, and saves ₹2–3 lakh in replacement costs, ensuring sustainable and cost-effective treatment for municipal and industrial applications.
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How are SKF Elixer’s STPs cost-effective solutions for wastewater treatment?
Our AABR-based STPs save ₹2–5 lakh annually through low energy use and water reuse for a 100 KLD plant. Subsidies and AMCs make them affordable, reducing healthcare costs by ₹5–10 lakh for rural communities.
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