Table of Contents
A Comprehensive Guide to Treatment Challenges
India generates over 72,000 million litres of sewage wastewater daily, much of it laden with diverse pollutants that threaten rivers, groundwater, and public health. Untreated discharge contributes to waterborne diseases affecting 20 million people annually, with economic losses exceeding ₹50,000 crore from healthcare and environmental cleanup.
Understanding sewage wastewater contaminants is crucial for effective management, as these impurities vary from organic matter to toxic chemicals, demanding tailored treatment approaches. At SKF Elixer, our Vulcan STP leverages advanced AABR technology to address these contaminants efficiently, transforming wastewater into reusable resources for industries, communities, and agriculture.
This blog breaks down the primary sewage wastewater contaminants, their sources, impacts, and measurement as water pollution indicators, alongside the sewage treatment process. Whether you’re an industrial manager in Ahmedabad grappling with effluent compliance or a municipal official in Lucknow planning upgrades, these insights will equip you to navigate wastewater challenges with SKF Elixer’s proven solutions.
Biological Oxygen Demand (BOD)
BOD measures the oxygen required by microorganisms to decompose organic matter in sewage, typically 200–400 mg/L in domestic wastewater. High BOD depletes dissolved oxygen in receiving waters, suffocating aquatic life and creating dead zones in rivers, where levels exceed 50 mg/L cause fish kills costing fisheries ₹10,000–₹20,000 per hectare annually.
Sources include food wastes, detergents, and human excreta, contributing 50–60% of sewage’s organic load. In a 100 KLD inflow (100,000 litres daily), BOD can reach 20–40 kilograms, straining treatment systems. CPCB norms limit effluent BOD to <20 mg/L for discharge or <10 mg/L for reuse.
Impacts: Elevated BOD leads to foul odours and eutrophication, with treatment failures in overloaded plants adding ₹50,000–₹1 lakh in operational costs monthly. For a hospital generating 50 KLD sewage, unchecked BOD risks fines of ₹1–5 lakh under pollution laws.
Chemical Oxygen Demand (COD)
COD indicates total oxidizable matter, including non-biodegradable organics, ranging 400–1,000 mg/L in sewage. It’s 2–3 times BOD, sourced from industrial discharges like textiles (adding dyes and solvents) and household chemicals.
High COD (above 250 mg/L effluent limit) corrodes pipes and inhibits biological treatment, increasing energy use by 20–30% in aeration (₹20,000 extra monthly for 100 KLD). In urban areas like Mumbai, mixed industrial-sewage COD spikes to 2,000 mg/L, polluting coastal waters and fisheries worth ₹5,000 crore yearly.
Measurement via dichromate oxidation helps predict treatment efficiency; ratios BOD:COD >0.5 indicate biodegradability.
Total Suspended Solids (TSS)
TSS encompasses particles like silt, organics, and debris, averaging 200–500 mg/L in raw sewage. From toilet paper, food scraps, and soil runoff, TSS clouds water, reducing light penetration and harming aquatic ecosystems.
Impacts: Clogs filters, raising maintenance ₹10,000–₹20,000 per incident, and carries pathogens, contributing to 30–40% of river pollution. Effluent TSS must be <50 mg/L; excess in a 200 KLD plant discharges 10–20 kilograms daily, silting water bodies and costing ₹50,000 in dredging.
In industrial sewage from food processing, TSS reaches 1,000 mg/L, necessitating pre-screening.
Total Dissolved Solids (TDS)
TDS includes inorganic salts, minerals, and organics dissolved in water, 500–1,500 mg/L in sewage. Sources: soaps, fertilizers, and urine (adding chlorides and phosphates).
High TDS (>500 mg/L for reuse) affects taste, corrodes equipment (₹5,000–₹10,000 yearly damage), and harms crops in irrigation reuse, reducing yields by 10–20% (₹20,000 loss per hectare). Measurement via evaporation or conductivity meters guides tertiary treatment.
Pathogens
Sewage teems with bacteria (E. coli 10^6–10^8 MPN/100 mL), viruses, and parasites from fecal matter. In India, pathogens cause 1.5 lakh diarrhea deaths yearly, with treatment lapses in 70% of urban plants.
Impacts: Outbreaks cost ₹5,000–₹15,000 per case in medical bills. Disinfection targets log-6 reduction (99.9999% removal) for safe discharge.
Nutrients (Nitrogen and Phosphorus)
Nitrogen (20–50 mg/L as ammonia) and phosphorus (5–10 mg/L) from urine, detergents, and food wastes fuel algal blooms, depleting oxygen and creating toxins. In lakes like Bangalore’s Bellandur, nutrient overload costs ₹10–20 crore in cleanup.
Effluent limits: total nitrogen <10 mg/L, phosphorus <2 mg/L. AABR in Vulcan STP achieves 80–90% removal via nitrification-denitrification.
Oil & Grease
From kitchens and garages, oil & grease (50–150 mg/L) form scum layers, inhibiting oxygen transfer and clogging systems (repairs ₹10,000–₹20,000 monthly).
Impacts: Harms wildlife and treatment efficiency; limits <10 mg/L for discharge. Skimming traps remove 70–80%.
Heavy Metals
Trace metals like lead (0.01–0.1 mg/L), chromium (0.05–0.5 mg/L) from industrial mixes or batteries bioaccumulate, causing neurological disorders costing ₹10,000–₹50,000 per affected person.
Sources: Tanneries add 1–5 mg/L chromium, polluting groundwater.
Limits: lead <0.01 mg/L. Adsorption or precipitation needed.
pH & Alkalinity
Sewage pH 6.5–8.5; extremes (<6 or >9) from acids/alkalis kill microbes, disrupting treatment. Alkalinity (200–500 mg/L as CaCO3) buffers pH but high levels scale equipment (₹5,000 cleaning).
Impacts: Corrodes pipes, adding ₹20,000 yearly maintenance.
Toxic Chemicals & Emerging Pollutants
Pesticides, pharmaceuticals (0.001–0.1 mg/L), and microplastics from detergents persist, endocrine-disrupting health. In sewage, antibiotics foster resistance, with treatment costs rising ₹50,000 per resistant case outbreak.
Advanced oxidation in modern STPs addresses these.
The Sewage Treatment Process: Addressing Contaminants
The process includes:
- Preliminary: Screens remove TSS (2–5 kilograms/1,000 litres).
- Primary: Sedimentation settles 50–60% TSS and 30% BOD.
- Secondary (Biological): AABR degrades BOD/COD (90–95% removal), nutrients via biofilms.
- Tertiary: Filters TDS, disinfects pathogens; handles metals via coagulation.
For 100 KLD, treats 90,000 litres outflow, reusing 80%.
How Vulcan STP Can Treat Wastewater Contaminants
SKF Elixer’s Vulcan STP with AABR excels:
- BOD/COD Reduction: Biofilms achieve <10 mg/L BOD, <50 mg/L COD in 5–500 KLD units.
- TSS/TDS: Media filtration removes 99% TSS; optional RO for TDS <100 mg/L.
- Pathogens/Nutrients: UV and denitrification ensure <100 MPN coliform, <10 mg/L nitrogen.
- Oil/Grease & Metals: Pre-traps and adsorption cut to <10 mg/L and trace levels.
- Efficiency: Low energy (0.5 kWh/KL), minimal sludge (30% less, ₹20,000 savings disposal).
- pH/Alkalinity: Auto-dosing maintains 7–8 pH.
- Emerging Pollutants: Activated carbon adsorbs chemicals.
For a 100 KLD hotel, Vulcan treats contaminants, reuses for flushing (saving ₹1 lakh water bills), with Stainless Steel construction lasting 20 years.
Conclusion
Sewage wastewater contaminants demand vigilant treatment to safeguard health and resources. STP Vulcan from SKF Elixer efficiently neutralizes these threats, promoting reuse and compliance. Adopt our AABR systems for sustainable operations.
Contact SKF Elixer today.
FAQs
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1. What is BOD, and why is it a key contaminant in sewage?
What is BOD, and why is it a key contaminant in sewage?
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2. . How does COD differ from BOD in sewage treatment?
COD (400–1,000 mg/L) includes non-biodegradable organics, 2–3x BOD, from chemicals; inhibits biology if high. Vulcan’s biofilms cut COD to <50 mg/L, saving ₹20,000 monthly energy in 100 KLD plants.
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3. What are the impacts of TSS and TDS on water quality?
TSS (200–500 mg/L) clouds water, clogs systems (₹10,000 repairs); TDS (500–1,500 mg/L) affects taste, corrodes (₹5,000 damage/year). Vulcan filters to <50 mg/L TSS and <500 mg/L TDS for safe discharge.
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4. How do pathogens and nutrients pollute sewage wastewater?
Pathogens (10^6 E. coli MPN/100 mL) cause diseases (1.5 lakh deaths/year); nutrients (20–50 mg/L nitrogen) trigger blooms (₹10–20 crore cleanup). Vulcan disinfects to <100 MPN, removes 80–90% nutrients.
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5. How does Vulcan STP treat heavy metals and emerging pollutants?
Vulcan uses adsorption/coagulation for metals (<0.01 mg/L lead), carbon for chemicals; AABR handles 5–500 KLD, ensuring compliance and reuse, saving ₹50,000 fines and ₹1 lakh water costs annually.
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