How Bioculture Removes Cyanide, Thiocyanate, and Phenol from Steel Plant Wastewater: A Complete Guide

The industrial wastewater generated by steel manufacturing units, particularly those that make or treat coal, turns out to be a poisonous cocktail of toxic chemicals like cyanide, thiocyanate, phenol, ammonia, etc. 

Despite being a serious threat to the environment, these pollutants can be treated biologically with the help of specially enhanced biocultures, which are the eco-friendliest and most powerful solution.

In this blog, we will go through, step by step, the bioculture that is dedicated to (specifically BactaServe bioculture) and has triumphed over the removal of cyanide, thiocyanate, and phenol from steel-plant wastewater, and what this means for the management of industrial effluent.

Why Cyanide, Thiocyanate & Phenol Matter in Steel Wastewater

The waste effluent produced by steel and coking processes is heavily polluted with toxic substances and contains free cyanide (CN⁻), thiocyanate (SCN⁻), phenolics, and ammonia (NH₃/NH₄⁺), along with suspended solids and organic load indicated as COD/BOD, among others. 

The main toxic compound is cyanide (CN⁻), which is a killer of aquatic life and even humans. Due to its extremely high toxicity, even tiny concentrations (parts of ppm) may result in death. Besides, many microbes do not survive in the presence of cyanide, which leads to difficulties in biological treatment.

Thiocyanate (SCN⁻): Created during the coking process and, although less toxic than cyanide, is more stable hence its presence in wastewater makes it difficult to remove; indirectly contributes to the organic matter concentration.

Phenol: A product derived from the coking process and a main pollutant in the waste water; the compound is toxic and very often goes through treatment processes without being reduced due to its high resistance to them.

The treatment of such wastewater not only requires the toxic species to be removed but also the organic load (COD/BOD), ammonia, and other contaminants to be reduced to acceptable levels with the least, if any, secondary hazardous byproduct generation.

Case Study Overview: Steel Plant + BactaServe Bioculture

The case in focus involves a steel plant (in eastern India) manufacturing plates, coils, pipes, and galvanized sheets. Their effluent treatment plant (ETP) had a capacity of 3,600 m³/day, with two aeration tanks (in series), pre- and post-anoxic tanks, and a membrane-bioreactor (MBR), followed by a reverse osmosis (RO) step for effluent recycling.

Inlet (Raw Effluent) Characteristics

According to the case study’s “Critical inlet parameters”:

Parameter	Typical Concentration (mg/L)
Cyanide (CN)	2.5 – 6.5
Thiocyanate (SCN)	300 – 350
Phenol (C₆H₅OH)	150 – 250
COD	1,300 – 1,800
BOD	500 – 800
Ammoniacal nitrogen (NH₃-N)	250 – 300
TDS	4,200 – 4,500 (with conductivity ~6,700 µS/cm)

These values show a heavy pollutant load, cyanide in ppm range, high SCN and phenol, and significant organic/nitrogen load.

The Bioculture Solution: How BactaServe Works

To remediate this complex wastewater, the plant applied BactaServe bioculture, a custom bacterial consortium formulated to degrade cyanide, thiocyanate, phenol, and to carry out nitrification/denitrification for nitrogen removal.

Bacterial Strains & their Roles

• Paracoccus spp. and other mixed microorganisms in the consortia were employed in Aeration Tank 1 subsequently thiocyanate neutralization.

  
  

• Different types of Pseudomonas spp. were utilized for phenol decontamination and they managed to decrease the phenol concentration from 250 ppm to approximately 2–2.5 ppm.

  
  

• Bacillus spp. (for instance Bacillus megatherium and B. amyloliquefaciens) were specifically aimed at the decrease of COD/BOD (i.e., the organic load).

  
  

• Nitrifiers like Nitrosomonas and Nitrobacter were the organisms used in Aeration Tank 2 to perform nitrification (converting NH₃-N to NO₃).

  
  

• Denitrifiers such as Thiobacillus were employed to carry out the denitrification process of nitrates into N₂ gas in the anoxic tanks.

This staged, multi-bacterial approach provided the best possible treatment for multiple pollutants: toxic organics (phenol), cyanide/thio-cyanide, nitrogen compounds, and overall organic load.

Treatment Duration & Dosing

The full remediation was achieved over a 45-day period, with regular dosing of the bioculture into the aeration tanks as per a predefined protocol.

Results: Dramatic Reduction of Pollutants

The performance data after bioculture + MBR treatment (outlet) is striking. According to the case study:

Parameter	Inlet (mg/L)	Outlet (after MBR) (mg/L)
COD	~1,376	104
BOD	280	8
Ammoniacal nitrogen (NH₃-N)	300	44.8
Nitrate (NO₃)	30	15.47
Total Kjeldahl Nitrogen (TKN)	200	60
Cyanide (CN)	6.5	0.031
Thiocyanate (SCN)	350	20
Phenol (C₆H₅OH)	250	2

Key takeaways:

• Cyanide dropped from 6.5 mg/L to 0.031 mg/L (≈ > 99.5 % removal).

  
  

• Phenol fell from 250 mg/L to ~2 mg/L, a remarkable ~99.2 % reduction.

  
  

• Thiocyanate reduced from 350 mg/L to 20 mg/L, indicating ~94 % removal.

  
  

• The reduction of COD by around 92.4% and the near elimination of BOD indicate a massive reduction of organic load. 

  
  

• On top of that also considerable nitrogen reduction: ammoniacal nitrogen has been reduced very much, nitrates have been cut down, TKN has been decreased, which means that the nitrification + denitrification cycles have been successful.

  
  

These numbers exemplify how effective a well-designed bioculture + ETP/MBR setup can be for steel plant wastewater.

Why Bioculture (Biological Treatment) Is Often Preferable

There are a variety of physical and chemical processes such as chemical oxidation, adsorption, and advanced oxidation to consider for the treatment of industrial effluent, but the application of bioculture through biological treatment presents many advantages regarding mixed pollutants (cyanide + SCN + phenol + nitrogen + organics) treatment. A few of the advantages are as follows:

Eco-friendly and chemical-free, for example: The use of biological methods do not, as a rule, lead to the generation of toxic chemicals or large amounts of sludge; the microorganisms assimilate contaminants into the products that are less injurious (for instance, ammonia, carbonates, sulfates, and nitrogen gas).

Cost-efficient: Once the living system is established, there will be less input of chemicals and less operational cost compared to some advanced oxidation or chemical treatments.

Removal of contaminants in a comprehensive way: This has been demonstrated in the case study, as a single bioculture setup is able to dynamically handle cyanide, thiocyanate, phenol, organic load, and nitrogen, which is difficult to achieve with isolated physicochemical approaches.

Flexibility: The use of bacterial consortia (instead of a single strain) provides better resilience and tolerance for varying loads while allowing the simultaneous degradation of multiple pollutants.

Scientific studies back this up: mixed microbial cultures have been demonstrated to degrade cyanide and thiocyanate efficiently, sometimes achieving cyanide removal > 99%.

Best Practices for Implementing Bioculture-Based Treatment in Steel Plants

If you’re considering a similar approach for your plant’s wastewater whether steel, coke, or other industrial effluent, here are some guidelines based on the case study + literature:

• Utilize a mixed bacterial community specifically designed to the purpose: BactaServe and similar cultures or genera combinations (like Pseudomonas, Bacillus, Paracoccus, Thiobacillus, etc.) are more efficient than mono-strain treatments since different microorganisms eliminate different waste materials (cyanide, SCN, phenol, nitrogen).

  
  

• Give microbes enough time to acclimatize & the right dosing schedule: The acclimatization period is required for the microbes to get used to very toxic conditions and to pollutants' load variations. The regular dosing over the period of days/weeks is very important.

  
  

• Support with correct reactor design and sequencing: Aerobic → anoxic → aerobic (or aeration + MBR + denitrification) approach gives a possibility to handle the organic load, nitrification/denitrification, and phenol & cyanide/SCN degradation step by step.

  
  

• Carefully monitor inlet and outlet parameters: (COD, BOD, CN, SCN, phenol, NH₃-N, TKN, nitrates, etc.) to ensure that they meet the requirements of discharge or recycling standards.

  
  

• Perform pre-treatment before the biological process (if required): Sometimes, it is beneficial to bioculture the microorganisms less by removing heavy oils, tar, or suspended solids beforehand.

  
  

What This Means for Environmental Compliance & Sustainability

Regulatory compliance: The levels of cyanide, SCN, and phenol being at ppb/low-ppm certainty that the discharge would not violate the limits and hence no environmental fines or backlash would occur.

Resource recovery & recycling: The integration of MBR and RO for post-treatment (as illustrated in the case study) allows for the reclaimed water to be used again, thus minimizing the need for the supply of freshwater.

Sustainability & ESG goals: Biological treatment fits perfectly with the green-manufacturing objectives, lessens the use of chemicals, and shows proper waste handling.

Scalability: The example indicates that a large capacity ETP (3,600 m³/day) can also be treated biologically making it an inspiring development for other heavy industry sectors.

Potential Limitations & Considerations

Bioculture-based treatment is powerful, but not a magic bullet. Some challenges to keep in mind:

• It is possible that high toxicity will eliminate the microbial activity, but first acclimatization would be very important.  

  
  

• There are still some compounds that might require additional treatment like residual SCN, trace organics, heavy metals.  

  
  

• The operational parameters, pH, temperature, dissolved oxygen, and retention time should be strictly regulated so as to ensure the survival and productivity of bacteria.  

  
  

• The mixed wastewater composition of heavy metals, sulfides, and fluctuating loads may necessitate the use of specific consortia and the implementation of pre-treatment steps.

  
  

Conclusion

The BactaServe bioculture case in the steel plant scenario stands as a proof that biological treatment can not only efficiently but also sustainably, deal with such a complex mixture of cytocidal, thiocyanate, phenol, and nitrogenous compounds in toxic wastewater. Through a precisely engineered bacterial consortium, multi-stage treatment (aerobic + anoxic + MBR), and careful supervision, the pollutant concentration in the effluent can be reduced from hundreds of ppm to just a few mg/L (or even ppb in case of cyanide). This process helps not only in compliance with legal and environmental standards, but also in the areas of water recycling and eco-friendly industrial operations.

For the steel, coke, or heavy industry sectors that want to have a lower impact on the environment, getting a bioculture-based ETP is not only feasible but also the most efficient and future-proof approach very often.

Frequently Asked Questions

How is cyanide biologically removed from steel plant wastewater?

Cyanide is biologically removed using specialized microbes that enzymatically convert free cyanide into less toxic compounds such as ammonia and carbonates. Certain bacterial strains can survive cyanide toxicity and use it as a nitrogen or carbon source, enabling safe degradation without forming secondary hazardous byproducts.

Why is thiocyanate difficult to remove from steel industry effluent?

Thiocyanate is more stable and persistent than free cyanide and does not degrade easily under conventional treatment. It requires specialized microbial consortia capable of breaking the sulfur–carbon–nitrogen bond, making biological treatment with acclimatized bioculture essential for effective removal.

Can bioculture treat cyanide, thiocyanate, and phenol simultaneously?

Yes. A properly engineered mixed bioculture can simultaneously degrade cyanide, thiocyanate, phenol, organic load (COD/BOD), and nitrogen compounds. Different bacterial strains work in parallel or sequentially, making bioculture-based treatment ideal for complex steel plant wastewater.

How long does bioculture treatment take to stabilize toxic steel wastewater?

In highly toxic steel plant effluent, full stabilization typically takes 30–60 days. This period allows microbial acclimatization, population growth, and gradual pollutant degradation. Treatment time depends on inlet toxicity, dosing strategy, reactor design, and operational control.

Is biological treatment safer than chemical oxidation for cyanide removal?

Yes. Biological treatment is safer because it avoids hazardous chemicals, reduces toxic sludge generation, and prevents the formation of secondary pollutants. Unlike chemical oxidation, bioculture converts cyanide into environmentally benign end products through natural metabolic pathways.

What inlet conditions are required for effective bioculture performance?

Effective bioculture performance requires controlled pH, adequate dissolved oxygen in aerobic zones, sufficient retention time, and gradual exposure to toxic loads. Pre-treatment to remove oils, tars, or solids may be required to protect microbial activity in highly polluted wastewater.

How does bioculture improve COD and BOD removal in steel plant ETPs?

Bioculture introduces bacteria that metabolize complex organic compounds into simpler molecules. This significantly reduces COD and BOD while improving oxygen utilization, stabilizing biomass, and enhancing overall ETP efficiency without excessive chemical dosing.

Can bioculture-based treatment meet discharge and reuse standards?

Yes. When combined with advanced biological processes like MBR and RO, bioculture-based ETPs can reduce cyanide to ppb levels, phenol to low ppm, and organics to compliant limits, enabling safe discharge or reuse in industrial recycling systems.

What role does acclimatization play in treating toxic industrial wastewater?

Acclimatization allows microbes to gradually adapt to extreme toxicity levels. Without acclimatization, cyanide and phenol can inhibit or kill bacteria. Controlled dosing and staged exposure are critical for building a resilient and effective microbial ecosystem.

Is bioculture treatment scalable for large steel plants?

Yes. Bioculture-based treatment is fully scalable and has been successfully applied in large ETPs handling thousands of cubic meters per day. With proper reactor design, monitoring, and microbial management, it is suitable for both medium and large steel manufacturing facilities.