Controlling odours is one of ...

Controlling odours is one of the most important - and yet most challenging - aspects of wastewater treatment. Foul odours are often a source of complaints, igniting objections from plant workers and neighbours alike.

Type of odour

Common odours lingering in and around treatment plants smell like rotten eggs, ammonia, or garlic, among other things. Sometimes the odor is described as earthy or organic.

How to reduce odour. step by step

There are two main types of technologies to treat odour: physical/chemical and biological. Physical/chemical technologies remove bad-smelling emissions by changing them with chemicals (chemical scrubbers), burning (incinerators) and by adsorbing the emissions with carbon. Biological technologies remove emissions using filter systems, made partially or completely from organic materials (bio filters), that pass the emissions upwards whilst simultaneously trickling a cleansing solution downwards (bio trickling filters). Other biological technologies aerate the sludge or sewage with fine bubbles (activated sludge diffusion). The first step in solving any odour problem is identifying the source. Odours could be coming from raw wastewater exposed to air at the influent pump station and primary clarifier stage. The ​only place you ​may find these ​are at the ​excess sludge ​treatment, ​where air ​circulation ​over a small ​activated ​carbon filter ​can do the job. ​

Bio filtration and active carbon filtration require the most materials. Incineration requires the most energy because it uses natural gas. Bio filtration uses the largest amount of land, with a footprint seven times greater than that of bio trickling filters and 25 times that of chemical scrubbers. However, bio trickling filters have the highest water consumption at 0.052 litres per m3 of treated gas per hour.

Two widely-applicable, emerging odour control technologies, known as activated sludge recycling (ASR) and oxidized ammonium recycling (OAR), have significant potential for WWTPs with low investment and operating costs. Although these technologies have been discussed in technical forums and applied at some WWTPs with promising results, they have not been explored using a systematic approach.

1. Activated sludge recycling.
2. oxidized ammonium recycling
3. There are many odours control technologies in the marketplace and no single, universally ideal solution exists. Some plants use deodorizing misting systems to target volatilized odours compounds in the air. Others choose to add chemicals directly to the water that react with odours-causing compounds. Fine-tuning the treatment process itself is another odour control tactic, albeit a more complex one.
4. Often the simplest approach to odour control is quite literally covering the problem. Many wastewater treatment plants choose to seal the source of odours - whether that’s a tank, basin, or lagoon - with an industrial-grade cover, thereby preventing the diffusion of odour vapours.
5. “Capture and treat” technology is an even more powerful odour control solution. This involves capturing odours by containing them with a cover, and then withdrawing and treating the collected foul air. Once the air is conveyed in a ductwork system, it can be treated by a variety of technologies such as a bio filter, wet scrubber, carbon filter, proprietary media, etc.
6. Covers not only reduce odour emissions but also help contain harmful greenhouse gases and minimize evaporation so that less water and chemicals need to be used in the wastewater treatment process.