By Derk Maat
Offensive odours generated by landfills, wastewater treatment plants, transfer stations, food waste receptacles, garbage trucks, composting operations, sewer systems, pumping stations, stormwater ponds, combined sewer overflow facilities, canals, and agricultural operations are a challenge, especially in urban environments.
Measurement of offensive fugitive odours has grown into a significant business, spawning new innovative technology to address the problem. Drone-based sampling devices have now been developed to measure odours above and around industrial facilities.
There has been significant progress in measuring, quantifying and source identification of odours generating nuisance complaints. Regulatory agencies are now able to identify facilities and plants responsible for odour generation and force these facilities to deal with them.
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Odour control technologies
Most of the new technology being developed is based on chemical breakdown of odours, using UV, carbon, ozone, and biological filtration. Other solutions include oxygenating and aerating solid and liquid waste collection basins to prevent septic conditions, which is an energy intensive practice. The least effective method is the use of chemical masking agents. These are often toxic and have human exposure restrictions.
Other initiatives and solutions have been based on the use of biocides to kill bacterial populations that are responsible for odour generation. Biocides currently in use consist of chlorine/quaternary ammonia, copper sulphate, and formaldehyde solutions which are highly toxic to the preferred beneficial bacteria and to the environment when discharged. These chemicals, when used as biocides, not only kill the offensive bacteria generating the odour, but also the bacteria responsible for treating the waste in composting or wastewater treatment operations.
Formaldehyde is used to kill odours in portable toilets. When the wastewater from these toilets is introduced into a municipal wastewater plant, it upsets and severely inhibits the biological processes in them, adversely affecting performance and effluent quality. Recovery time to rebuild bacterial populations can be weeks.
Selective biological inhibition of odour producing bacteria
A new biological and environmentally sustainable approach using plant based organic micronutrients has been developed over the last number of years to specifically stimulate aerobes and anaerobes and competitively inhibit the sulphur reducing and ammonia forming bacteria and enzymes.
The main active ingredients in the micronutrient solutions include plant sourced amino acids, vitamins and other plant based organic constituents and trace minerals. The micronutrient solution itself is biodegradable, as it is used up as food source by the beneficial bacteria found in organic waste streams.
These micronutrients, when added to liquid and solid organic waste streams, eliminate the formation of odours during the biological reactions that are responsible for organic waste degradation. Research has shown that non sulphur reducing anaerobes and many different types of aerobes are stimulated by the plant based organic micronutrient catalyst to operate at much higher metabolic rates. Sulphur reducing anaerobes and ammonia generating enzymes are unable to utilize the specific micronutrients introduced into organic waste streams.
As a result, the microorganisms stimulated by the micronutrient solution outcompete the odour producing microbes for macronutrients. Competitive inhibition severely restricts the metabolic activity of odour producing microbes, which dramatically decreases the production of odorous gases.
The net impact is that odours are significantly reduced, but bacterial breakdown of the organic waste continues at an accelerated rate.
Benefits of biological inhibition of odour producing bacteria
Biological inhibition of odour producing bacteria has been observed in sewer systems, wastewater plants, septic tanks, lagoons, composting facilities, stormwater retention ponds or combined sewer overflow ponds where the micronutrient solutions have been added. If micronutrient control of odour generation is implemented, there is no need to revert to aerating septic systems, tanks, lagoons or ponds, or treatment facilities to control and/or treat odours.
The advantages with biological source control of odours with micronutrients include:
Eliminates the need for significant infrastructure and space requirements to contain, control and treat odours.
Eliminates 90% of the capital investment associated with odour control using chemical and/or biofilter infrastructure.
Eliminates 90% of the energy demand associated with conventional odour control strategies and technologies, which reduces the overall carbon footprint.
The use of plant based organic micronutrients represents a near zero carbon footprint solution to eliminate odours. There is an immediate return on the investment for micronutrient usage as it replaces or eliminates the costly operation of biofilters, ozonation units, and carbon units.
Treatment of airborne odorous compounds
Plant based organic micronutrients can also be utilized in misting systems to treat odorous gases generated by nonpoint sources of odours in facility operations like transfer stations, landfills, garbage rooms in commercial facilities, wastewater plants, biosolids processing facilities, and organic material processing facilities like food production plants and/or pulp and paper mills.
Micronutrients can also be used to improve the capacity and performance of biofilters and wetscrubbers. Plant based micronutrients, when diluted in ratios varying from 100 – 1,000:1, react with airborne odour molecules in chemical oxidation reactions to render them odour free.
The micronutrient solutions contain no masking agents except in some cases where a tracer fragrance is required. Also, they do not contain any bacteria or enzymes that may be subject to regulatory restrictions, or any minerals in concentrations harmful to the environment. When added to the waste streams they inhibit the formation of hydrogen sulphide, ammonia, trimethylamine, methyl mercaptans, and other non-identified sulphur reduced organic compounds.
Sci-Corp has carried out a controlled laboratory study to measure the effectiveness of these micronutrient products when added to decaying organic waste. Two reactors with an enclosed head space, a control and a test reactor, were set up containing 1 kg each of decaying food waste. The test reactor was treated with a one time 5 ml dose of Biologic SRC.
The reactors were equipped with sampling ports to sample headspace gases and were incubated at a temperature of 30°C to represent warm weather conditions. The reactors were sampled every 12 hours over a five day period. Air bag samples were sent to a certified laboratory and analysed by gas chromatography mass spectrometry for the four compounds listed above. The reactors were also subjected to a simple olfactory test by the technician.
The control sample was characterized by a highly putrefied odour. The treated sample was free of any objectionable odours.
The laboratory tests confirmed that a one-time dose was effective over a five day time period to suppress the generation of odorous gases by 70% – 85% from organic waste incubated at a temperature of 30°C.
These results have significant implications for the source mitigation of odours from green bins, composters, transfer stations, landfills and wastewater treatment facilities. Further testing has confirmed that solid organic waste degradation rates were increased by up to 65% under laboratory and field conditions.
Misting/spraying applications
Air misting in a hog slaughterhouse barn and in hog rearing facilities resulted in 85% – 90% reduction in H₂S/ammonia concentrations in the atmosphere. Air misting in poultry barns has shown similar results. Commercial misting applications in garbage rooms of stores and institutions achieved similar reductions.
Misting applications in municipal solid waste (MSW) transfer stations, landfill sites, tipping floor and pits in a MSW incineration plant, and chicken-rendering plants have all resulted in dramatic odour reduction and elimination of neighbouring odour complaints. Industrial misting applications of the micronutrient solutions in tannery facilities and sludge processing facilities also resulted in significant odour reductions.
Misting into biofilters improves the performance of biofilms and also complexes odour molecules into non odour generating compounds.
Wastewater treatment plant applications
When applied in wastewater plants for odour control, the micronutrients were also able to improve wastewater treatment performance and reduce operating costs. The typical addition rates for odour control in wastewater plants range from 1 ppm (domestic wastewater) to 10 ppm (industrial wastewater).
Application to biosolids processing plants at 50 ppm to 2% TSS sludge mixtures also reduced odours by 80%. Application in wastewater treatment plant influents by direct injection has also resulted in dramatic reduction in ambient air H₂S reductions, as illustrated in Table 1.
Lagoon and combined sewer overflow pond surface spray applications have eliminated odour generation and odour complaints from lagoons containing effluent from ethanol plants, paper mills, septic tank sludges, hog manure, and cherry processing facilities, ranging in volume from 500 m3 to 45,000 m3.
Inoculation of 2% solids sludges from paper mills and wastewater plants prior to dewatering has reduced odours 80% – 90% and eliminated the need for large biofilters, scrubbers and contaminated air treatment facilities by reducing and/or eliminating the generation of odours at source.
Plant based micronutrient environmental certifications
Biologic SRC/SRC3 plant based micronutrient products are manufactured and sold by Scicorp International Corp. They have been tested and certified non-toxic by a leading toxicity laboratory (TOX Monitor/BSR, Inc. Illinois U.S). They are also certified within the Ecologo/UL program.
In conclusion, the use of micronutrient solutions for odour source control and odour abatement and stimulation of beneficial biodegradation mechanisms represents an alternative innovative but proven environmentally sustainable approach.
Derk Z. Maat, M.Eng., P.Eng., is with Maat Environmental Engineering. This article appears in ES&E Magazine’s April 2019 issue.
