For metalworking businesses, keeping a clean and compliant operation can seem to be a big task, and it is a big task considering how much waste is produced and how waste can go in water systems and the air free if no precautions are taken.
Fortunately, technological advances in filtration means companies are being able to remove pollutants in a more effective way that does not cost extra dollars.
Read on to learn about how biological filtration is changing the way industrial organizations like metalworking companies remove contaminants.
What Is Biological Filtration?
Biological filtration leverages living organisms mainly bacteria to breakdown and eliminate contaminants from water or air, rendering them safer for environmental discharge or consumption.
When occurring in water treatment these micro-organisms will grow on a filter medium (sand, gravel, plastic or any other porous material) forming a biofilm.
As water (or air) passes through the filter, the pollutants become trapped into it, the microorganisms will then metabolize the pollutants as nutrients converting toxic compounds (for example, ammonia, organic material, and some chemical compounds) into less harmful bye products (for example,) nitrates or carbon dioxide.
With these natural mechanisms of controlling pollution in biological filtration, it can be seen as yet another form of filtration. Some examples are:
- Wastewater treatment plants: Typically, bacteria operating in biofilters break down organic material and nutrients, improving the quality of water that is subsequently discharged into the environment.
- Ponds and aquariums: Beneficial bacteria will convert the toxic ammonia from fish waste to less harmful nitrates, which can be absorbed by plants.
- Air pollution control: Biofiltration is also applied for cleaning contaminated air, where microorganisms are processing airborne pollution while air flows through a specifically designed media.
The major mechanisms are, adsorption (binding of pollutants to the filter media), absorption (uptake by microorganism or by the media), and biodegradation (the enzymatic conversion of a pollutant into a non-hazardous substance).
Biological filtration is widely accepted based on its natural sustainable approach to pollution control. This ease of use minimizes the need for chemical treatments and allows for a clean and safe working environment while helping to ensure a high quality of air or water.
How Biological Filtration Works
Biological filtration is cheating contaminants from water to protect the environment and make sure industrial companies don’t discharge harmful byproducts into bodies of water. In this biological filtration process, good bacteria eat volatile organic contaminants (VOCs).
VOCs can cause pollution (smog) and health issues (respiratory issues) if left untreated. Good bacteria act as a filter, which consumes VOCs and other waste, digesting grease, VOCs, and harmful waste from the water.
Biological filtration is a natural solution to help our ecosystem stay healthy. Organizations can utilize this filtration method to avoid ever reaching for cleaning chemicals that could be doing more harm than good.
Types of Biological Filtration Systems
Depending on the application and pollutant load, metal facilities may choose from several biofiltration technologies including:
- Biofilters. These systems include a packed bed of either organic or inorganic media (e.g. peat, bark, compost, or plastic). Air passes through the media, and microorganisms on the media surface degrade sites.
- Biotrickling Filters. In these systems, a continuous flow of either water or nutrient solution “trickles” over a packed bed of material and microorganisms (biofilms) are growing on it. When treating gaseous pollutants, biotrickling filters may be effective in treating those contaminants with greater solubility.
- Bioscrubbers. These systems use a combination of scrubbing and biological degradation. The contaminated gas is absorbed into a scrubbing liquid, and the liquid is then treated biologically in a separate bioreactor.
- Moving Bed Biofilm Reactors (MBBRs). MBBRs are more common for wastewater treatment, and the systems have small plastic carriers that provide surface area for biofilm growth. MBBR systems are particularly effective in treating industrial effluent with heavy metals and organic pollutants.
Selecting the Right System
Biological filtration media is just a home for the microbial population that ultimately does the work of filtering the air or water. It is important to understand that not attempting to be selective when designing a wastewater treatment system may compromise or have a negative impact on a systems effectiveness.
Some systems are able to use filter foam while others utilize wood mulch. Other forms of media can include ceramic rings or lava rock that can generally promote bacterial growth.
Not using appropriate media can create problems for companies. The filtration system may be able to create a colony but may not be able to maintain that colony and ultimately brings no value to the cleaning process.
Facilities should investigate the options available for media specific to the process used at mbbrmediadirect.com and, in any case, use consultants that can develop a good understanding of the facilities needs.
Why Metal Facilities Rely on Biological Filtration
Metal processing plants face unique pollution challenges, like VOCs, odors, and heavy metals. Here’s how biological filtration can help.
1. Volatile Organic Compound (VOCs) control.
Many metal processes are solvent-based, thus releasing VOCs into the atmosphere. VOCs are harmful organic pollutants that can contribute to serious health effects (as in pollutants that are harmful to humans) as well as ground-level ozone and smog.
Biological solution: Biofilters, bio trickling filters, etc. can remove VOCs in a variety of biofilter designs by allowing their breakdown into less harmful substances i.e. carbon dioxide and water by attached biofilm bacteria.
2. Odor control.
Metal finishing, pickling, and wastewater treatment processes can release harmful and nasty odors, such as hydrogen sulfide (H₂S), ammonia, carbonyls, mercaptans, etc.
Biological solution: Good anaerobic biological solutions can be implemented that harness specific microbial communities to target and neutralize odors in air, which not only will clean up the odor issue (a good thing for working conditions), but might also reduce complaints from adjacent communities.
3. Wastewater heavy metals treatment.
Metal industry wastewater will frequently contain toxic heavy metals including (but not limited to) lead, chromium, cadmium, nickel, etc. Often, heavy metals are non-biodegradable.
Biological solution: Some innovative engineered bacteria strains and biofilms can immobilize or biosorb heavy metals thus removing them from water as biomass or altering their state into a “less harmful” inert, non-mobile, sludge-like products.
4. Cost efficiency.
Biological filtration is usually less expensive to operate than thermal oxidizers or chemical scrubbers. After you have established a biological filtration system, its operation is largely dependent upon naturally occurring biological processes, with low energy threshold systems.
Cost benefit: The ongoing operation and maintenance costs of biofiltration are less over time – which may appeal to more industrial plants interested in reducing their carbon footprint whilst still being economically friendly.
5. Compliance.
Environmental protection agencies in many countries have started to mandate air emissions and water quality regulations for industrial operations. Some types of biological filtration systems can help metal facilities comply with:
- Clean Air Act (U.S.)
- EPA MACT standards
- Water discharge permits
- Local odor control ordinances
Compliance is a good deterrent to attracting fines, legal challenges, and bad publicity.
Advantages of Bio-Filtration for Metal Industries
- Eco-Friendly: Bio-filtration takes an eco-friendly approach by utilizing natural capabilities of microbes and avoids the use of harmful, destructive chemicals.
- Flexible: Bio-filtration systems can be used in a small shop or in very large complex industrial facilities.
- Low Energy Operation: Bio-filtering operates without the combustion energy requirements of thermal oxidizers.
- Sustain Changing Contaminants: Microbial systems can accept change in contaminant concentrations.
- Multi-Pollutant with the Same Treatment: Certain biological treatment systems can remove VOCs, odors and some inorganic contaminants in the same system.
Challenges and Considerations
Although biological filtration can be an effective alternative to chemical treatment, it poses several challenges in a harsh industrial setting such as metal processing.
1. Environmental Sensitivity.
Microorganisms depend on specific temperature, humidity, and pH ranges to operate efficiently. If those ranges are exceeded, effectiveness and operating capacity can be reduced.
Solution: Pretreatment systems, such as ion-exchange units or bottled products, can improve the stability of the stream; continuous monitoring can also enhance stability and efficiency.
2. Replacement of Biofilter Media.
Over time the filter media itself can degrade, clog, or become bio fouled and require replacement.
Solution: Using synthetic, engineered media will increase service life.
3. Toxicity of Metals to Microbes.
Metals can be toxic to microbial populations when above acceptable limits.
Solution: Controlled dosing rates, prefiltration, or using a metal resistant strain of microbes can alleviate this challenge.
4. Start-up Time.
The start-up time to establish a healthy, effective microbial population varies.
Solution: Some systems will use bioaugmentation, or, in effect, use a preserved microorganism or pre-grown system.
Real World Cases
1. Zinc Plating Facility (USA).
A zinc electroplating facility used a biotrickling filter to remove VOCs and H₂S from it’s wastewater treatment unit. The results were a 90% reduction in odor complaints and VOCs were well below regulated amounts.
2. Steel Foundry (Germany).
A steel foundry now has a modular biofiltration unit instead of chemical scrubbers. The biological system decreased operational costs by 40% and met EU air quality standards.
3. Metal Coating Plant (India).
MBBR system helped this plant treat their wastewater which had high COD. The plant started with engineered microbes and after coasting time got over 85% COD removal which allowed them to discharge into the municipality safely.
Conclusion
Biological filtration is an impressive blend of natural science and industrial desire. Microbes provide a needed option to clean polluted air and water, meet regulations, be environmentally responsible, and save operating costs for metal facilities.
There are definitely challenges – such as openness to interference by environmental factors, and toxicity concerns with metals – but it is clear that both microbial engineering and system designs are progressing to make biological filtration increasingly effective and reliable.
In the metal industry, pollution control is both a regulatory and social obligation, and biological filtration offers a sustainable-development solution.