Field of activity
Service supplied by Labiotest
Type of action
The process of purifying civil wastewater takes place in several stages, during which pollutants are transformed, decomposed and eliminated. As a result, the purified water can be reintroduced into the environment not only without causing problems, but by initiating a positive recycling circle.
However, wastewater treatment plants can generate foul odors and thus cause problems for citizens residing near the plants.
The latter is the case of a company in central Italy that operates a civil wastewater treatment plant, which requested our intervention to assess the status of the controls in its plant for the abatement of odorigenic emissions generated by different treatment sections.
The situation was critical, so we decided to collaborate with two other companies that together with Labiotest are part of 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:
In the first phase, the data collected directly at the site were essential to identify existing critical issues and find possible solutions for intervention in the wastewater treatment plant. Together with the client, we decided to jointly intervene on the most critical principals.
The intervention included an initial phase of sizing and design of the new facilities and a subsequent phase of supply, installation and testing.
Our revamping service SOS Service brought the abatement principals back to maximum efficiency by improving the situation of the wastewater treatment plant.
Let's see in detail how.
The chemical components of odorous contaminants are very complex and mainly composed of H2S, NH3 and VOCs.
VOCs in wastewater treatment plants are generally divided into several categories: sulfur compounds, nitrogen compounds, halogens and its derivatives, hydrocarbons, and oxygen-containing organic compounds.
After the company contacted us, our technicians carried out an on-site inspection from which it was found that the presidium serving the vents of the 2 centrifuges in the sludge dewatering room was undersized to abate the concentrations of H2S and VOCs present from the exhaust gas stream.
In addition, the room did not have adequate ventilation of the ambient air considering the fact that periodic maintenance activities were planned inside it performed by maintenance technicians.
With the support of Gesteco's Analytical Laboratory and the LOD Olfactometric Laboratory, it was possible to conduct an accurate screening of various chemical compounds in order to uniquely identify the compounds present in the greatest quantity and responsible for odors and to quantify odors from the most critical areas through olfactometric analysis.
Specifically, compounds such as: hydrogen sulfide and mercaptans, ammonia, volatile organic compounds, total organic carbon and methane, amines and amides, phenols and aldehydes were searched for.
On the basis of the results obtained from the analyses and taking advantage of the know-how of the Gesteco Laboratory and, to the synergistic work of LOD and Labiotest, it was possible to properly design and size an odor abatement plant capable of significantly reducing emissions from chemical agents and odors in accordance with the requirements of current regulations.
After a careful review of the areas to be treated and the technical feasibility, we proposed to implement a multi-stage odor abatement plant. This included the installation of a new air treatment system from the sludge dewatering room (estimated 6 changes/hour) and two centrifuges totaling 6,500 cu m/h 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. stack emission.
The plant sections provided in the odor abatement plant are:
1. Local suction piping
The suction piping complex makes it possible to convey the aeriform flow to the equipment.
2. Basic scrubber/oxidizer unit
Wet scrubber tower and associated local control panel of installed equipment.
The control panel allows the scrubber to be operated, the electric fan to be powered, and the flow rate to be modulated according to the actual process needs thanks to the frequency variator.
Coalescing filter. This unit is in charge of reducing the moisture in the flow in transit.
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 the chemical and physical characteristics of the odorigenic molecules to be eliminated. The filter system consists of one or more static beds composed 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 chosen so as to draw in the amount of air strictly necessary according to the process at hand, thus reducing operating costs.
The impeller is made with suitable profiles to ensure maximum flexibility in terms of performance.
6. Connecting piping and expulsion stack
The accompanying piping complex makes it possible to convey the aeriform flow through the various treatment units to the centrifugal fan and expulsion stack.
The system was installed and started up directly by our technicians.
In the testing phase, olfactometric measurements were conducted, which demonstrated the high efficiency of nuisance odor abatement.
The initial stages of site survey and analytical verification were essential to present the most suitable proposal to the client to meet the expectations and requirements.
The multistage plant now guarantees odor abatement efficiency of more than 90 percent and that there are no risks to humans and the environment.