Biological Wastewater Treatment

TL;DR: Biological wastewater treatment is a secondary treatment process where microorganisms (primarily Bacillus and Pseudomonas species) decompose organic pollutants in industrial effluent and domestic sewage. It operates through two methods — aerobic (with oxygen, faster, higher energy cost) and anaerobic (without oxygen, slower, produces biogas). In India, only 28% of the 72,368 MLD of urban sewage generated daily is treated, making efficient biological treatment solutions critical. This guide covers treatment types, technologies (ASP, MBBR, MBR, SBR, UASB), microbial selection, operational parameters, troubleshooting, and advanced bioculture solutions for ETP and STP systems.

Biological wastewater treatment is a natural, eco-friendly process that uses beneficial microorganisms to decompose organic matter and remove contaminants from water, making it safe for discharge or reuse.

Developed in the early 20th century, this proven technology remains the most effective and sustainable method for treating both industrial effluent and domestic sewage worldwide.

Our wastewater treatment solutions harness advanced microbial cultures — a proven alternative for effective sewage treatment and industrial wastewater treatment, straight from Nature’s Laboratory.

With Organica Biotech’s specialized bioformulation for wastewater treatment and a little help from nature, you can reduce sludge volume and operational costs, curb foul odour, and significantly lower COD and BOD levels in the water.

What Is Biological Wastewater Treatment?

Biological wastewater treatment is a secondary treatment process that uses naturally occurring microorganisms to decompose organic pollutants in industrial effluent and domestic sewage.

The microbes consume organic matter as their food source, converting highly toxic contaminants into harmless byproducts such as CO₂, water, and biomass.

It is the most widely used method for secondary treatment worldwide, deployed through aerobic (oxygen-present) and anaerobic (oxygen-absent) systems.

In simple terms, it is a system where microbes are put to work cleaning wastewater.

These powerful microorganisms break down organic matter and help remove contaminants that physical treatment alone cannot eliminate.

On the surface, the concept may seem simple, but the treatment process is complex, with multiple variables at play.

Various factors related to biology, biochemistry, and engineering impact the efficiency of the process.

Biological wastewater treatment occurs after primary (physical) treatment, where solid waste, sediments, and substances like oil are removed using screens and filters.

In the secondary stage, biological treatment takes place under aerobic or anaerobic conditions in a bioreactor — an apparatus or system in which a biochemical process involving microorganisms takes place.

The treated wastewater, commonly called effluent, is then released into the environment or further polished through tertiary treatment.

What Are the Types of Biological Wastewater Treatment?

Biological wastewater treatment is of two primary types: aerobic (uses oxygen) and anaerobic (does not use oxygen).

The choice between them depends on the effluent characteristics, available space, energy recovery goals, and operational budget.

In many industrial plants, both aerobic and anaerobic processes are coupled together for maximum treatment efficiency.

Aerobic Wastewater Treatment

In the aerobic biological process, microbes act on organic waste and suspended solids in the presence of a sufficient amount of dissolved oxygen (typically 1–2 mg/L).

The process converts waste and releases carbon dioxide, water, and other by-products.

Factors like temperature, pH, and oxygen availability are important parameters that help microbes degrade waste efficiently.

Aerobic treatment is carried out in aerobic tanks, oxidation ponds, and surface aeration systems.

The process also includes activated sludge and aerobic digestion, with aeration systems maintaining a continuous oxygen supply.

A rich mixture of the bacterial population, blended with maximum nutrients and oxygen, drives rapid bacterial growth and respiration, decomposing organic matter and producing sludge.

Gradually, sludge and waste separate from the water, leaving clean water behind.

Aerobic treatment is most commonly used for treating domestic and industrial wastewater containing an extensive amount of organic matter.

It provides faster treatment (hours to days) but requires higher energy input due to continuous aeration.

Anaerobic Wastewater Treatment

Anaerobic wastewater treatment uses bacterial populations to decompose organic waste in the absence of oxygen, converting contaminants into carbon dioxide, methane, and other end-products.

It is mainly used in the agricultural and food processing industries to treat wastewater with strong organic content.

One of the major advantages of anaerobic treatment is energy recovery. Anaerobic digestion converts waste into methane, which is used to produce biogas — a renewable energy source.

The process involves multiple stages: hydrolysis, acidogenesis, acetogenesis, and methanogenesis, where different microbial communities act as substrates at each phase.

Anaerobic systems must be completely closed and provided with heat. While the process requires longer retention time and larger space, it offers significantly lower operational costs and produces considerably less sludge than aerobic treatment.

Aerobic vs. Anaerobic Wastewater Treatment: Key Differences

The main difference is that aerobic treatment utilises microbes requiring oxygen to respire and degrade organic matter, while anaerobic treatment degrades organic matter in the absence of oxygen.

Selecting the right process depends on several factors:

• Availability of Land: Anaerobic processes require higher retention time, so space requirements are greater.
• Cost of Operations: Aerobic facilities have higher OPEX costs due to continuous oxygen supply and maintenance. Anaerobic processes are comparatively cost-effective as they require no additional energy input.
• Effluent Type and Energy Recovery: When effluent contains high organic content, energy can be recovered as biogas via anaerobic treatment. Aerobic energy recovery is limited to organic sludge with suitable substrates.

Anaerobic treatment is usually chosen when the organic load is excessively high or the wastewater contains xenobiotic compounds (tough to degrade biologically).

Many industries deploy both aerobic and anaerobic treatment processes for comprehensive treatment.

What Technologies Are Used in Biological Wastewater Treatment?

Several technologies are used for the biological treatment of wastewater, including Activated Sludge Process (ASP), Trickling Filters, MBBR, UASB, and aerated lagoons.

The selection depends on the type of industrial effluent, the parameters to be treated, and space availability.

Regardless of the technology chosen, the efficiency of treatment ultimately depends on the efficiency of the microbial culture inhabiting the secondary treatment unit.

1. Activated Sludge Process (ASP)

The activated sludge process is the most prominent and widely used aerobic biological wastewater treatment method globally.

Microbes under oxygenated conditions form biological solids called activated sludge, which absorb dissolved organic matter and reduce BOD (Biological Oxygen Demand).

How It Works:

• Wastewater is mixed with activated sludge in an aeration tank
• Continuous oxygen supply is provided through an aeration system
• Microbes multiply rapidly and metabolize organic waste
• Sludge settles in a secondary clarifier
• ~30% of sludge is recirculated to the aeration tank (Return Activated Sludge — RAS)
• Excess sludge is removed (Waste Activated Sludge — WAS)

Variations: Extended Aeration, Sequencing Batch Reactors (SBR), Membrane Bioreactor (MBR), Moving Bed Biofilm Reactor (MBBR)

2. Trickling Filter System

A fixed-film biological treatment system consisting of a bed of stones, rocks, or plastic media.

Wastewater is sprayed continuously over the media, trickling down as microbes colonize the surface, absorb contaminants, form a biomass layer, and lower BOD.

Natural air circulation provides oxygen throughout the process.

Advantages: Lower energy consumption, simple operation, and handles variable loads well.

3. Oxidation Pond (Aerated Lagoon)

Oxidation ponds are large, shallow earth basins where wastewater is treated through a symbiotic relationship between microbes, algae, and sunlight.

Algae perform photosynthesis, releasing oxygen that aerobic bacteria use to decompose organic matter.

The bacteria release CO₂, which algae use for growth, creating a self-sustaining ecosystem.

Best for: Small communities, agricultural operations, areas with ample land and sunlight. Typical retention time is 20–50 days.

Other Established Technologies

Additional technologies for industrial effluent treatment include Moving Bed Biofilm Reactor (MBBR), Membrane Bioreactor (MBR), Sequencing Batch Reactors (SBR), Rotating Biological Contactor (RBC), Upflow Anaerobic Sludge Blanket (UASB), anaerobic lagoons, anoxic reactors, aerobic granular sludge technology, and anammox systems.

What Role Do Microorganisms Play in Wastewater Treatment?

Microorganisms are intrinsic to the secondary treatment of wastewater — they act as nature’s recyclers, transforming pollutants into harmless byproducts while creating a self-sustaining ecosystem within treatment systems.

In biological wastewater treatment, microbes consume organic material as a source of carbon, nitrogen, phosphorus, and other essential nutrients for growth.

In return, they convert highly toxic contaminants into smaller, less toxic materials that can be safely discharged into the environment.

Common Bacterial Species in Wastewater Treatment

The most common bacteria used as bioculture for wastewater treatment are Bacillus and Pseudomonas species.

Bacillus Species:

• B. licheniformis — Degrades proteins and complex organics
• B. subtilis — Breaks down fats and oils
• B. megaterium — Phosphate solubilization
• B. pumilus — Enzyme production for organic breakdown
• B. coagulans — Acid-tolerant organic degradation

Pseudomonas Species:

• P. aeruginosa — Degrades aromatic compounds
• P. putida — Breaks down complex hydrocarbons
• P. fluorescens — Biodegrades various organic pollutants

How Are Microbes Selected for Treatment?

The basis for choosing microbial culture for wastewater treatment is the organisms’ genetic and enzymatic machinery, which enables them to degrade substrates found in certain types of wastewater.

Selection criteria include:

• Genetic Machinery: Ability to produce specific enzymes for target pollutants
• Substrate Specificity: Capacity to degrade compounds in specific wastewater types
• Tolerance: Ability to withstand extreme pH, temperature, and toxic conditions
• Growth Rate: Rapid multiplication under treatment conditions
• Flocculation Ability: Capacity to form stable aggregates for easy separation

Higher Life Forms as System Health Indicators

Apart from bacteria, higher life forms such as free-swimming ciliates, stalked ciliates, rotifers, and tardigrades play an important role in biological wastewater treatment systems.

They feed on free bacterial cells, help maintain good flocculation, and serve as reliable indicators of system health.

These organisms are highly sensitive to changes in the treatment environment.

Their absence indicates high toxicity (due to toxic compounds, high COD, high TDS, or extreme pH), while their presence and type reveal the stage and age of sludge development.

What Are the Stages of Wastewater Treatment?

The wastewater treatment process consists of three stages: primary treatment (physical), secondary treatment (biological), and tertiary treatment (advanced polishing).

Biological wastewater treatment occurs in the secondary stage, which is the most critical phase for organic pollutant removal.

Primary Treatment (Physical Process)

Primary treatment removes large solid materials from incoming water.

Bar screening filters out wood, plastic, rags, and other debris. A primary clarifier then allows solids to settle by gravity, sometimes with the help of coagulants and flocculants to precipitate dissolved solids.

The remaining liquid, known as effluent, still contains organic contaminants measured as BOD (Biological Oxygen Demand).

BOD is the amount of oxygen required by aerobic microbes to decompose organic matter in aquatic environments.

An increased BOD level is harmful to water resources and can severely affect aquatic ecosystems.

Secondary Treatment (Biological Process)

Secondary treatment — also known as biological wastewater treatment — is the microbe-mediated treatment of wastewater from the primary clarifier.

It uses biological processes to reduce and remove biodegradable organic matter, contaminants, and suspended solids that escape primary treatment.

Treatment plants provide suitable environments for naturally occurring microbes to thrive and act aggressively on organic matter.

The microbes feed on organic impurities for growth and release by-products such as carbon dioxide, water, and energy.

The process involves aerobic, anaerobic, or a combination of both to treat wastewater by reducing COD, nitrogen, and phosphorus to levels that meet environmental standards.

Tertiary Treatment (Advanced Treatment)

The tertiary stage is the final stage, improving water quality to a level that allows safe discharge into the environment or reuse of treated water.

It involves processes such as disinfection, membrane filtration, and carbon filtration.

What Are the Types of Wastewater?

Depending on its source, wastewater is classified as domestic wastewater (sewage) or industrial wastewater (effluent).

Both types require treatment before discharge, but their characteristics — and therefore their treatment approaches — differ significantly.

Industrial wastewater from sectors such as sugar, pulp and paper, food processing, distilleries, dairies, tanneries, and pharmaceuticals often contains hazardous chemicals, including lead, nickel, zinc, and pathogens.

When discharged without adequate treatment, it becomes a significant source of environmental pollution and public health hazards.

What Types of Wastewater Treatment Plants Exist?

The three most common types of wastewater treatment plants are Effluent Treatment Plants (ETP), Sewage Treatment Plants (STP), and Common Effluent Treatment Plants (CETP). Each serves different wastewater sources and is designed accordingly.

Effluent Treatment Plants (ETP)

ETPs are used by industries with high manufacturing capacities — textile, pharmaceutical, and chemical industries — where wastewater contains organic or inorganic compounds with high COD, TDS, and extreme pH.

ETPs are selected and designed according to the type and volume of industrial effluent generated.

Sewage Treatment Plants (STP)

STPs remove contaminants from domestic wastewater generated by residential colonies, institutions, and the hospitality industry. STPs handle wastewater with high organic content that can be treated with relatively less difficulty compared to industrial effluent.

Common Effluent Treatment Plants (CETP)

CETPs treat wastewater from various small-scale industries unable to treat their effluents on-site. They are usually constructed in industrial estates or industrial development corporations.

• Explore our comprehensive guide to various wastewater treatment plants for an in-depth comparison.

What Parameters Affect Biological Wastewater Treatment Performance?

Optimal growth of microorganisms in a wastewater treatment system requires a balanced functioning of several bio-environmental parameters.

Temperature, pH, nutrients, toxic materials, dissolved oxygen, and the Carbon:Nitrogen: Phosphate (C:N:P) ratio all influence bacterial performance and treatment efficiency.

These elements must be checked regularly to maintain a sufficient microbial population.

Understanding Residence Time (MCRT)

Residence time — also known as Mean Cell Residence Time (MCRT) — describes how long microorganisms remain in the activated sludge system to interact with and degrade organic matter.

It is calculated by dividing the volume of the secondary tank by the flow rate of the effluent.

A well-balanced residence time (typically 5–15 days for conventional activated sludge) allows optimum degradation of pollutants and determines microbial community composition.

How Do You Monitor Biological System Health?

Maintaining the desired microbial population is essential to optimize secondary wastewater treatment efficacy.

The biological health of the system must be monitored at regular intervals using a combination of microscopic examination, laboratory analysis, and physical observation.

Microscopic Examination

Regular microscopic analysis reveals floc density and structure, free bacterial cell count, types and abundance of higher life forms, filamentous bacteria density, and protozoa diversity.

This gives an inside view into the biological health of the system.

Microbial Count Analysis

Microbial count analysis helps determine total microbial count per millilitre, microbial diversity indices, specific bacterial populations, and pathogen levels in the effluent sample.

Physical Indicators

Observable characteristics without laboratory equipment include:

• Odor: Earthy smell indicates a healthy system; foul odors suggest anaerobic conditions or toxicity
• Color: Dark brown suggests good treatment; black indicates anaerobic conditions; light brown may indicate low MLSS levels
• Turbidity: Clear supernatant indicates good settling; cloudy suggests poor flocculation
• Foam: Minimal white foam is normal; excessive brown foam suggests filamentous bacteria overgrowth

What Are Common Problems in Biological Treatment Systems?

A breakdown of the secondary biological treatment system is usually associated with reduced growth of desirable microorganisms or increased growth of undesirable ones, leading to lower COD reduction, reduced nitrogen removal, and excessive foaming.

Understanding these problems — and their causes — is essential for maintaining treatment efficiency.

How to Prevent Shock Loads

A shock load is any sudden change in effluent parameters that disturbs the secondary treatment ecosystem.

Several factors can trigger shock loading:

• Aeration Failure: A reduction in dissolved oxygen creates an anoxic environment, promoting undesirable microflora growth
• Toxic Compound Entry: Highly toxic compounds entering effluent streams can hamper microbial growth, reducing MLSS in the secondary system
• pH Fluctuation: A sudden shift toward extreme acidity or alkalinity can devastate the microbial population
• Flow Rate Variation: Large fluctuations in the inflow/outflow rate alter the organic loading rate and residence time

Monitoring and maintaining the characteristics of incoming effluent is essential to ensure the smooth functioning of the treatment plant and prevent shock loads.

Which Industries Need Biological Wastewater Treatment?

Any manufacturing industry producing wastewater with organic loads, toxic compounds, high COD, nitrates, phosphates, or TDS levels must treat its effluents before discharge.

Biological wastewater treatment is the primary method for organic pollutant removal across these sectors:

• Pharmaceutical: High COD, antibiotics, solvents
• Food & Beverage: High BOD, fats, oils, grease
• Dairy Processing: Lactose, proteins, high organic load
• Distillery: Extremely high BOD/COD, dark color
• Chemical Manufacturing: Toxic compounds, extreme pH
• Petrochemical: Hydrocarbons, phenols, sulfides
• Textile & Dyes: Color, high TDS, toxic dyes
• Pulp & Paper: Lignin, high COD, color
• Tannery: Chromium, sulfides, high BOD
• Sugar Processing: High BOD, suspended solids

Uses of Treated Wastewater

When properly treated to environmental standards, wastewater can be reused for:

• Industrial Applications: Cooling water, boiler feed, process water
• Agricultural Use: Irrigation of non-food crops, greenbelts
• Landscaping: Parks, golf courses, highway medians
• Construction: Concrete curing, dust suppression
• Municipal Use: Toilet flushing, firefighting
• Groundwater Recharge: Aquifer replenishment

This reuse significantly reduces demand on freshwater resources and promotes sustainable water management.

India’s Wastewater Crisis: The Scale of the Challenge

India faces a wastewater treatment deficit of staggering proportions.

According to the Central Pollution Control Board (CPCB) 2020-21 assessment, the country generates 72,368 MLD (million litres per day) of urban sewage — nearly double the rural generation of 39,604 MLD — yet only 28% receives treatment.

The remaining 72% (52,132 MLD) is discharged untreated into rivers, lakes, and groundwater.

Current Treatment Gap (2020-21 CPCB Data)

• 31,841 MLD installed sewage treatment capacity (only 43.9% of generation) [Source: CPCB Urban Wastewater Report]
• 26,869 MLD operational capacity (84% of installed capacity actually working)
• 20,236 MLD actual treatment (only 28% of sewage generated) [Source: Down to Earth CPCB Analysis]
• 44,000 MLD industrial wastewater generated, with approximately 6.2 billion litres remaining untreated daily [Source: ScienceDirect 2021]

Future Projections (2025–2050)

• 75–80% increase in wastewater generation projected over the next 25 years
• Total sewage generation to reach 130,000 MLD by 2045-46 [Source: Centre for Science and Environment Report, March 2025]
• 416 million additional urban residents by 2050 in India
• Urban population to reach 50% of total by 2050 (currently 35%) [Source: India Wastewater Treatment Market Report 2024]

Global Context (UN Water 2024)

Globally, only 38% of industrial wastewater is treated, and just 27% is safely treated to meet environmental standards.

An estimated 42% of household wastewater globally is not safely treated, releasing approximately 113 billion m³ into the environment annually. [Source: UN Water Progress Report, August 2024]

With projections showing water availability could drop below 1,000 m³ per capita per year — classifying India as “water scarce” — the urgency for efficient biological wastewater treatment has never been greater.

Since building new treatment plants is cost-prohibitive at the required scale, the most viable solution is enhancing the efficiency of existing treatment systems through advanced biological solutions.

Why Cow Dung Is Not the Best Solution for Wastewater Treatment

Cow dung is sometimes used as a bacterial culture source in wastewater treatment, but it is unsuitable for industrial applications.

Cow dung contains microorganisms from the cattle’s gut adapted to digest cattle feed, not industrial pollutants.

When transferred to a completely different and harsh effluent environment, these organisms cannot treat wastewater efficiently.

• Wrong Microbial Profile: Contains gut bacteria adapted to cattle feed, not industrial pollutants
• Pathogen Introduction: Carries harmful pathogenic bacteria that can negatively impact treatment processes and, when released into the environment, cause health hazards
• Ineffective Treatment: Cannot adapt to harsh industrial wastewater conditions
• Variable Composition: Inconsistent microbial populations make standardized treatment impossible

There is no substitute for a well-researched, tailor-made bacterial culture for wastewater treatment that is specifically designed for the effluent and treatment process.

Advanced Biological Treatment Solutions from Organica Biotech

With over 25 years of expertise, a DSIR-accredited R&D laboratory, and ECOCERT certification, Organica Biotech offers a wide range of customized microbial remediation solutions for wastewater treatment from both industrial and domestic sources.

Cleanmaxx® Product Range

Cleanmaxx® Aero (for aerobic systems), Cleanmaxx® ANB (for anaerobic systems), and Cleanmaxx® STP (for sewage treatment) are bioculture products containing highly aggressive microbes capable of degrading high organic loads.

These solutions deliver:

• Maximum BOD/COD reduction from wastewater
• Minimum sludge production (30–50% reduction)
• Foul odour neutralization by competing with pathogens
• Resilience under shock loads and variable conditions
• No modification required to the existing system setup

Organica Biotech also offers specialized solutions: Cleanmaxx® FOG for fats, oil, and grease degradation, and Microbster — a 100% natural nutrient additive blend of nitrogen, phosphorus, and micronutrients crucial to biomass development.

These advanced bio-augmentation products contain specially cultivated microorganisms that withstand extreme conditions, degrade specific industrial pollutants efficiently, and maintain high activity under variable loading — making them the ideal solution for powering the biological process in secondary wastewater treatment.

Explore our proven results: See how Organica Biotech’s solutions have transformed wastewater treatment across industries, or request a free sample to test in your plant.

Frequently Asked Questions (FAQs)

General Treatment Questions

1. My aerobic wastewater system is not working efficiently. Which microbial culture can help?

First, contact one of our experts for a system assessment. For aerobic systems, Cleanmaxx® Aero is one of the most effective biological wastewater treatment enzymes.

This bio-enzyme contains a specialized, heterogeneous consortium of uniquely functional bacteria with high proliferative capacity, capable of withstanding and treating hostile effluent water.

2. How can I increase biogas production and treatment efficiency in my anaerobic system?

Anaerobic wastewater systems are sensitive and require diverse microbes to complete hydrolysis, acidogenesis, acetogenesis, and methanogenesis.

Cleanmaxx® ANB provides a highly diverse mix of facultative anaerobes that strengthen and stabilize anaerobic systems, maximizing COD-BOD reduction while enhancing biogas production capacity and minimizing sludge volume.

3. I need nutrients for my biological system. How can Organica Biotech help?

Maintaining the correct C:N:P ratio is critical for good treatment efficiency. Microbster is a 100% natural, eco-friendly nutrient additive — a blend of nitrogen, phosphorus, micronutrients, and biostimulants crucial to biomass development in sewage and industrial wastewater treatment.

Our experts will guide you through the dosing process.

4. I have excessive fats, oils, and grease buildup, causing foul odours. What should I do?

Cleanmaxx® FOG is specifically developed for degrading excessive buildup of fats, oils, and grease.

Its selectively cultivated, target-specific microbes get activated when mixed with water, completely degrading organic waste during wastewater treatment and curbing foul odour emission.

5. My STP cannot handle tough urban waters with high organic load. How does Cleanmaxx STP help?

Cleanmaxx® STP works in two steps: first, breaking complex compounds into simpler polymers, then further degrading them into carbon dioxide and water.

It contains specialized bacterial strains that survive and perform under shock loads, effectively degrading the majority of man-made and natural contaminants present in municipal wastewater.

6. How do I assess the current health of my biological system?

Organica Biotech’s BioCheck study analyzes the current health and status of the biological system at your sewage or industrial wastewater treatment plant. Contact our team to schedule an assessment.

7. Do all microbes perform in biological wastewater treatment with equal efficiency?

No. Microbes show greater biological diversity than any other life forms on the planet. Depending on the environment, food source, and the microbe’s genetics, their capacity to degrade different kinds of waste varies.

In industrial wastewater treatment, the primary factor determining performance is the type of effluent and treatment method.

The key to efficient treatment lies in choosing the right microbial partner for your specific plant conditions.

8. Can I reduce ammonia through secondary treatment of wastewater?

Yes. Ammonia concentration can be reduced through microbial action in a two-step process: first, ammonia is oxidized to nitrites and nitrates (nitrification), then nitrates are reduced to nitrogen gas (denitrification).

Denitrification is especially crucial since releasing nitrates into the environment causes eutrophication and algal blooms.

9. How do I achieve efficient COD reduction when my effluent contains high TDS?

High total dissolved solids restrict microbial growth due to osmotic stress. The microorganisms in Cleanmaxx are specially selected for their ability to sustain high TDS effluents and still provide efficient COD reduction in industrial wastewater treatment plants.

Operational and Troubleshooting Questions

10. Are filamentous bacteria in my biological treatment plant a cause for worry?

In small amounts, filamentous bacteria are desirable — they form the backbone of floc formation, leading to healthy sludge.

However, a high density of filamentous bacteria indicates that the food-to-microbe (F/M) ratio, pH, or dissolved oxygen may not be optimal.

Investigate the root cause promptly, as continued presence leads to heavy foaming and reduced treatment efficiency.

11. How do I analyse the toxicity of the effluent in my plant?

The presence of higher life forms (ciliates, flagellates, rotifers) indicates non-toxic or very low-toxicity effluent.

Their absence — along with a reduced microbial count — indicates toxic conditions requiring additional treatment before biological processing.

12. Can I reduce the toxicity of my effluent using biological treatment?

Yes, microbial action can break down high molecular weight toxic compounds into smaller molecules that microbes use as a food source, reducing overall toxicity. This must be tested at a pilot scale first.

Organica Biotech’s BioSure method tests the efficacy of bioremediation products using effluent from your plant, providing a realistic scenario and solution.

13. How do I decide the volume and rate of sludge wasting?

Sludge recirculation is usually decided based on MLSS and MLVSS levels present in your system and the settling characteristics of your sludge. Regular SVI measurement helps optimise this balance.

14. How can I understand treatment plant efficiency without a microscope?

In the absence of laboratory equipment, physical characteristics of the effluent provide reliable indicators: odor (earthy = healthy; foul = distress), color (dark brown = good; black = anaerobic conditions), turbidity, and foam characteristics.

Additionally, estimating the Sludge Volume Index (SVI) reveals sludge development and settling ability in the aeration tank.

15. What is the ideal DO level for a wastewater treatment plant?

A dissolved oxygen level between 1 and 2 mg/L is typically maintained. Low DO levels hamper microbial growth and reduce treatment efficiency, while excessively high DO may indicate reduced MLSS or toxic stream entry.

16. How can I replicate biological wastewater treatment at a pilot scale?

Replicating the actual biological process in a lab is difficult.

Organica Biotech’s specially designed BioSure method tests the efficacy of our wastewater bioremediation products using effluent from your plant, providing a realistic pilot-scale scenario before full-scale deployment.

17. Should I add microorganisms to the primary tank?

Normally, it is not advisable. In primary treatment tanks, conditions may not be conducive for microbial growth — high amounts of alum, polyelectrolytes, or other chemical settling agents, along with fluctuating pH, are harmful to microbes. Microbial cultures should be introduced at the secondary treatment stage.

18. Does the presence of heavy metals affect secondary treatment?

Heavy metals are toxic to microorganisms and can hinder their growth. The microbes in Cleanmaxx can survive in the presence of moderate heavy metal concentrations.

However, high concentrations require chemical scrubbing and other pre-treatment methods before the effluent undergoes biological treatment.

19. Can both organic and inorganic components be treated biologically?

Technically, microorganisms can only use organic compounds as their primary food source.

However, certain microbial strains can also consume some inorganic compounds — provided you have the right bacterial culture in your biological units.

The key is selecting the appropriate microbial formulation for your specific effluent composition.

20. Which pathogen removal method is best for wastewater?

Pathogens — microorganisms harmful to humans, animals, or aquatic life — can be removed through chemical, physical, or biological processes during secondary and tertiary treatment steps.

The choice depends on contamination levels and the required environmental, health, and safety standards. Typically, a combination of biological treatment followed by tertiary disinfection provides the most effective pathogen removal.

The Future of Biological Wastewater Treatment

Biological wastewater treatment remains the most sustainable, cost-effective, and environmentally responsible method for managing both industrial and domestic wastewater.

Since its development in the early 20th century, it has become the backbone of wastewater treatment globally.

However, the scale of the challenge has intensified dramatically.

With India generating 72,368 MLD of urban sewage daily but treating only 28%, and projections showing a 75–80% increase in wastewater generation over the next 25 years, the urgency for action has never been greater.

Success in biological wastewater treatment depends on:

• Understanding the specific characteristics of your wastewater
• Selecting appropriate treatment technologies and microbial cultures
• Maintaining optimal operating parameters consistently
• Regular monitoring and proactive system management
• Investing in specialized bioculture solutions for complex wastewaters

Modern advancements in microbial cultivation, genetic understanding, and bio-augmentation technologies have made it possible to treat increasingly complex wastewater streams while reducing operational costs and environmental impact.

By combining proven biological processes with innovative microbial solutions, industries and municipalities can achieve regulatory compliance, protect water resources, and contribute to sustainable water management for future generations.

Biological wastewater treatment harnesses the power of naturally occurring microorganisms to transform pollutants into harmless substances.

Whether through aerobic processes that rely on oxygen or anaerobic systems that work without it, these microscopic workers provide an eco-friendly, cost-effective solution for one of humanity’s most pressing environmental challenges — the safe treatment and reuse of water.

Note on Data Sources: Statistics in this article are sourced from Central Pollution Control Board (CPCB) reports for 2020-21, Centre for Science and Environment (CSE) assessments from 2024-25, UN Water reports (2024), Down to Earth research publications, and peer-reviewed market research reports. All statistics are hyperlinked to their original sources for verification.