Cases study

Odor abatement in a wastewater treatment plant

Revamping and construction of a multistage plant, with wet scrubber tower and dry filter, to abate odorigenic emissions from civil wastewater treatment.

Field of activity


Specific activity

Civil wastewater treatment


Central Italy


The emission of foul smells was originating from centrifugal exhaust fans in the sludge dewatering hall

Service supplied by Labiotest

SOS Service: analysis, design, implementation of treatment plant and efficiencies monitoring

Type of action

Monitoring and evaluation of existing equipment, design and implementation of multi-stage odors and contaminants abatement plant

The process of purifying civil wastewater takes place in several steps, allowing for pollutants to be transformed, decomposed and eliminated. As a result, it is possible to reintroduce purified water into the environment, not only without causing problems, but also by starting a positive recycling circle.

However, wastewater treatment plants can generate foul smells and thus cause problems for people living in plants neighborhood.

The latter is the case of a company in central Italy operating a civil wastewater treatment plant that requested our intervention to assess the status of its plant equipment for the abatement of odorigenic emissions generating from various treatment sections.

The situation was critical, so we decided to collaborate with two other companies that together with Labiotest belong to the Luci Group: Gesteco, particularly its division specializing in chemical analysis, and the olfactometric analysis laboratory LOD.

Through this collaboration, we carried out chemical and odorimetric characterization of emissions to identify:

  • types of contaminants at the origin of odor nuisances and their concentrations;

  • odor content to be abated to ensure legal limits enforced for such equipment.

In the first phase, the data collected directly on site were essential to identify existing critical issues and find possible solutions for action regarding the wastewater treatment plant. Together with the client, we decided to act together on the most critical elements.

The intervention included an initial phase of sizing and design of new facilities and a subsequent phase of supply, installation and testing.

Our revamping service SOS Service brought the abatement equipment back to maximum efficiency by improving the situation of the wastewater treatment plant.

Let us see how.

Problem in the wastewater treatment plant

The chemical components of odorous contaminants are very complex and mainly consist in H2S, NH3 and VOCs.

Generally speaking, VOCs in wastewater treatment plants are divided into more categories: sulfur compounds, nitrogen compounds, halogens and its derivatives, hydrocarbons, and organic compounds containing oxygen.

After the company contacted us, our technicians carried out an on-site inspection, which permitted to ascertain that the equipment servicing vents of 2 centrifuges in the sludge dewatering hall was undersized to abate the concentrations of H2S and VOCs deriving from the exhaust gas stream.

In addition, the hall did not have adequate ambient air ventilation considering that maintenance technicians performed periodic maintenance activities inside. 

Chemical and olfactometric analysis

With the support of Gesteco's Analytical Laboratory and LOD Olfactometric Laboratory, it was possible to ensure an accurate screening of various chemical compounds in order to identify single specific compounds present in the largest quantity as responsible for odors, as well as quantify odors from the most critical areas through olfactometric analysis.

Specifically, the survey implied compounds such as: hydrogen sulfide and mercaptans, ammonia, volatile organic compounds, total organic carbon and methane, amines and amides, phenols and aldehydes.

Based on results obtained from analyses and with the help of Gesteco Laboratory know-how, together with LOD and Labiotest work, it was possible to properly design and size an odor abatement plant able to significantly reduce emissions deriving from chemical agents and odors in accordance with the requirements of current regulations.

Odor abatement plant: design and implementation

After a careful survey of areas to be treated and a control on technical feasibility, we proposed to implement a multi-stage odor abatement plant. This included the installation of a new treatment system for the air coming from the sludge dewatering hall (estimating 6 exchanges/hour) and two centrifuges totaling 6,500 m/h3 consisting of:

1. absorption in basic/oxidizing solution;

2. condensate separation through a PVC honeycomb demister;

3. physical and chemical adsorption with neutralization and oxidation of pollutants in the emission;

4. intake fan;

5. emission stack.

The plant sections provided in the odor abatement plant are:

1. Local suction piping
The suction piping makes it possible to convey the aeriform flow to the equipment.

2. Basic scrubber/oxidizer unit
Wet scrubber tower and associated local control panel for installed equipment.
The suction piping makes it possible to convey the aeriform flow to the equipment.

3. Demister
Coalescing filter. This unit is in charge of reducing the moisture in the transiting flow.

4. DKFIL unit
DKFil dry filter unit, equipped with an internal demister, sized and designed according to the flow rate of the emission to be treated and chemical and physical characteristics of odorigenic molecules to be eliminated. The filter system consists of one or more static beds, made of multiple adsorbent and chemically reactive layers that operate selectively and synergistically against the different substances in the aeriform effluent being treated.

5. Fan unit
The centrifugal fan was selected to draw in an amount of air strictly necessary according to the process taking place, thus reducing operation costs.The impeller is made with suitable profiles to ensure maximum flexibility in terms of performance.

6. Connecting piping and exhaust stack
The piping makes it possible to convey the aeriform flow through various treatment units, all the way to the centrifugal fan and expulsion stack.

Installation and testing

Our technicians installed and started up the system directly.

In the testing phase, olfactometric measurements took place, and demonstrated the high efficiency of nuisance odor abatement.

Odor abatement results obtained

The initial stages of site survey and analytical verification were essential to present the most suitable proposal to the client to meet expectations and requirements.

The multistage plant now guarantees odor abatement efficiency of more than 90 percent and ensures there are no risks to humans and the environment.

In addition, plant maintenance costs are now proportionate to the actual criticality.