Odour control for wastewater

Odour control for wastewater

From what once used to be an afterthought, the control of odours has now become a necessary primary consideration at a facility design phase.

The issue with wastewater isn’t only present in the immediate instance of unpleasant odours or bacterial exposure, it spreads further to surrounding areas that may include residential areas.

In an area which has a higher temperature, malodorous emissions are typically worse with other factors to be taken into consideration such as wind velocity and direction. Naturally, summertime is often the peak of odour complaints.

Luckily for industries, the controlling of unwanted odours at facilities is achievable with a variety of technologies to choose from. There are two main technologies that focus on different aspects of odour control – vapour phase and liquid phase.

Vapour phase technologies focus on the source of the odour issue such as a wet well or headwork. A ventilation system is installed at the source to help maintain a negative pressure to prevent any leakage of malodorous emissions from any vents, access hatches, etc. The vapour phase technology is most effective at preventing unwanted emissions from a specific source of issue.

The most flexible and reliable vapour phase technology, when it comes to odour control for wastewater, is wet air scrubbing. Wet air scrubbing has proven to be highly effective when treating water soluble contaminants, hydrogen sulphide, organic odours, as well as aiding in the removal of ammonia.

Chemical usage is necessary in this design due to the requirement of treating contaminants such as hydrogen sulphide with sodium hydroxide, as well as other malodorous compounds with sodium hypochlorite.

In order to reduce the chemical usage, a wet air scrubbing unit can be designed to perform as a multi-stage scrubbing system, which eliminates the need for sodium hypochlorite in the process to remove hydrogen sulphide.

Biofiltration has become a popular technology for odour control in wastewater due to the advantages of low installation, operation, and maintenance cost. It is effective in treating a variety of biodegradable and water-soluble contaminants.

Contaminants pass through the organic biofilter medium and are absorbed and degraded by the microorganisms populating the media.

Although biofilters have proven to be highly effective in the removal of sulphur-based odour compounds the likes of hydrogen sulphide, organic sulphide and mercaptans, they are considered to be ineffective in the removal of nitrogen-based compounds like ammonia and amines.

A carbon adsorption system works by way of an air stream passing over a carbon adsorbent bed. The simplicity of the technology works due to malodorous compounds being naturally attracted to the carbon adsorbent, which then adsorbs and degrades the contaminants.

One of the highest attractions to utilising a carbon adsorption system is the absence of any chemical supply to the technology. Similar to how biofilters work, carbon adsorption systems are effective in removing sulphide-based compounds but not so effective in removing nitrogen-based compounds.

Due to the discrepancies of effectiveness of each odour control technology, it is crucial to analyses and examine an industrial setting to understand the contaminants needed to be removed before implementing any such system.

Liquid phase technologies focus on the flow rate of wastewater and/or the total mass of contaminants present. This technology involves treating the wastewater stream to control unwanted odours being emitted from that stream.

Liquid phase treatments are mostly found in wastewater collection sites and not in wastewater treatment plants.

Due to the wastewater source being treated as opposed to the wastewater being treated alone, liquid phase technologies pride themselves in odour control as well as corrosion control.

The latter control naturally happens as a result of the removal of hydrogen sulphide which acts as a nuisance for corroding pipes and other structures dealing with water.

Richard Tonkin, general manager at Bulbeck Enviro, has been in his position with the company since 2014.

Bulbeck Enviro helps customers navigate the environmental compliance maze, through various products and services in water treatment, marine oil spill; odour control; medical waste and portable incinerators; hydrocarbon and chemical spill prevention, containment and clean-up.

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