sodium/calcium nitrate can be directly added to oxidation ponds that have become anaerobic. Ferric salts and magnesium hydroxide can also be added to wastewater to make the sulphur unavailable for forming odorous compounds. These techniques would typically form part of an odour control regime and are not adequate on their own. Photo 5: Biological scrubber at wastewater treatment plant Source: Ken Holyoake, Armatec Environmental Ltd Photo 6: Air abatement system featuring air collection ducting, scrubber to remove particulate and odour, fan to move air, and stack for final dispersion Source: Ken Holyoake, Armatec Environmental Ltd Dilution and dispersion Dilution and dispersion are usually achieved via emission through a tall stack. A stack is generally only appropriate for very low-intensity or non-offensive odours, discharged at low rates and as a final step following treatment of an odorous gas stream. The stack should be appropriately designed to ensure it is an adequate height above buildings in the vicinity, and this may require dispersion modelling. Guidance on appropriate stack design is available from the United States Environmental Protection Agency (1985). Efflux velocity is an important consideration and there should be an unrestricted final vertical discharge (ie, hooked vents or rain caps that restrict flow should be avoided). Dispersion has a moderate capital cost but low running costs. Masking compounds and ‘neutralising’ agents Masking compounds and neutralising agents are products available for treating fugitive odours such as from landfill working faces, fellmongeries, intensive farming of animals, and wastewater treatment plants. The systems to apply these compounds can require significant capital expenditure and ongoing costs. Few (if any) agents are well proven. Certain agents should not be used for specific activities (such as use of certain chemicals in poultry sheds, which cause residue issues). Available products can be classified as follows: Masking agents are mixtures of aromatic oils that cover up an objectionable odour with a more desirable one. Take extreme care with the use of masking agents, because the combination of chemicals can result in an odour that is even more offensive or objectionable. Chemical neutralising agents are typically proprietary mixtures containing oxidising or other chemically reactive agents that purport to neutralise certain odorous compounds.
sodium/calcium nitrate can be directly added to oxidation ponds that have become anaerobic. Ferric salts and magnesium hydroxide can also be added to wastewater to make the sulphur unavailable for forming odorous compounds. These techniques would typically form part of an odour control regime and are not adequate on their own. Photo 5: Biological scrubber at wastewater treatment plant Source: Ken Holyoake, Armatec Environmental Ltd Photo 6: Air abatement system featuring air collection ducting, scrubber to remove particulate and odour, fan to move air, and stack for final dispersion Source: Ken Holyoake, Armatec Environmental Ltd Dilution and dispersion Dilution and dispersion are usually achieved via emission through a tall stack. A stack is generally only appropriate for very low-intensity or non-offensive odours, discharged at low rates and as a final step following treatment of an odorous gas stream. The stack should be appropriately designed to ensure it is an adequate height above buildings in the vicinity, and this may require dispersion modelling. Guidance on appropriate stack design is available from the United States Environmental Protection Agency (1985). Efflux velocity is an important consideration and there should be an unrestricted final vertical discharge (ie, hooked vents or rain caps that restrict flow should be avoided). Dispersion has a moderate capital cost but low running costs. Masking compounds and ‘neutralising’ agents Masking compounds and neutralising agents are products available for treating fugitive odours such as from landfill working faces, fellmongeries, intensive farming of animals, and wastewater treatment plants. The systems to apply these compounds can require significant capital expenditure and ongoing costs. Few (if any) agents are well proven. Certain agents should not be used for specific activities (such as use of certain chemicals in poultry sheds, which cause residue issues). Available products can be classified as follows: Masking agents are mixtures of aromatic oils that cover up an objectionable odour with a more desirable one. Take extreme care with the use of masking agents, because the combination of chemicals can result in an odour that is even more offensive or objectionable. Chemical neutralising agents are typically proprietary mixtures containing oxidising or other chemically reactive agents that purport to neutralise certain odorous compounds.