Odour control has moved from an afterthought to a primary design consideration for most collection and treatment facilities.

By Annejan Visser, process engineer at QFS

 

Intensive urbanisation, incremental population growth, and seasonal temperature rises within metropolitan areas have increased the likelihood of exposure to odour generating facilities. This, together with the additional need for corrosion control of waste pipelines and the health and safety of municipal personnel, has made odour control requirements more prevalent in recent times.

Quality Filtration Systems (QFS) identified the local need for improved odour control measures at wastewater treatment plants and other odour generating sources, which led to the company concluding a technology partnership with Integrity Municipal Systems (IMS). Based in Poway, California, IMS is an odour-specific engineering company with over 20 years’ experience devoted to the design, manufacture and supply of innovative, preassembled odour solutions for the water and wastewater industry.

Cost-effective vapour phase technologies available include:

• biofiltration – a biological technology with low operating costs (I-BOxTM Biological Oxidation Systems)
• wet or chemical scrubbing – a reliable technology for chemical treatment
• adsorption – a well-established technology using dry media (BCS Series bulk carbon adsorbers).

In selecting a cost-effective odour control solution, it’s important to note the following important parameters:

• required air flow or ventilation rate
• the peak and average hydrogen sulfide (H₂S) concentrations in the odorous air
• the required level of odour removal (concentration of H₂S and odour units).

What sets IMS’s systems apart from other commercially available high-volume chemical scrubbers is the small construction footprint required for treating large air volumes. The chemical package system offered provides key advantages, such as:

• unitary construction of the treatment vessel
• a fibreglass exhaust fan with longer durability
• vessel deck for ease of access to equipment.

Current developments have also been made with IMS to provide ‘high-capacity’ activated carbon for towers that are:

• water regenerable
• naturally high in minerals
• sulfur selective.

Biotrickling filters (utilising sulfur-oxidising bacteria to biologically oxidise the H₂S and other sulfur compounds to soluble sulfates) is another technology proving popular at municipal facilities.

Among the benefits of the I-BOx biotrickling system is its ability to accommodate high air flow rates. For example, the I-BOx can accommodate flow rates of 450 m³/h per m² compared to 100 m³/h per m² for conventional organic biofilters. Other advantages include the long media life of the inorganic media utilised, due to the preferential development of autotrophic bacteria, and quick acclimation of bacteria on media to start immediate H₂S removal.

The system targets inorganic (H₂S) and organic odours, has a compact design due to a skid-mounted assembly, and a low operating cost. The other great advantage of the biotrickling system is the longevity of the media compared to carbon absorbers. Important to note with biotrickling filtration is the generation of sulfuric acid, which requires adequate sealing and bunding of the system, as well as the proper disposal of the waste sulfuric acid generated.

QFS recently installed and now operates six I-BOx systems at Cape Flats valve chambers, with another system installed at Reeston WWTW in East London. Both are functioning optimally.