Avoiding problems associated with foul odors in and around collectors and waste water treatment plants is today one of the major focus points to avoid possible issues related to worker safety, as well as minimizing negative social discomforts caused by the foul odors.
The main sources that generate foul odors in WWTPs occur at stages of anaerobiosis, where the lack of oxygen favours the development of the sulphate-reducing bacteria that convert the sulphates present in the system into H2S in collectors and pumping stations.
BIOCONSERVACION has recently signed a contract with SIMTEJO (Grupo Águas de Portugal) for the filtration media replacement in several pumping stations located in Lisbon (Portugal).
The goal of the project is to maintain H2S concentration levels below 1 ppmv
SIMTEJO is a reference company in Portugal that has as a main strategic objective controlling pollution in water resources. Thus, collecting and treating contaminants generated in domestic and industrial activities, protecting water resources and ensuring that the water returns to nature free of contaminants, are the main goals. SIMTEJO aims to contribute to the welfare of about 1.5 million people in a geographical area of around 1000 km2.
Characteristics of Pumping Station
All pumping stations have similar types and concentrations of pollutants, which increases significantly during summer season.
The pumping stations are located outdoors except a few of them which are underground due to urban location.
The purification systems have been implemented are basically standard vessels working in up-flow mode. However, in some pumping stations, where higher airflow rates must be treated, annular scrubbers have been favored to achieve an optimal performance.
Characterization of Emmissions
Pumping stations generally have a wide range of different volatile organic compounds (VOCs), H2S in concentrations of 10-30 ppmv and other contaminants such as NH3 or mercaptans or others, depending of the nature of the waste. Occasionally, H2S concentration can peak as high as 100-200 ppmv . The goal is to reduce the H2S concentration levels below 1 ppmv as well as eliminate the rest of odorous contaminants.
Taking into account the nature of the contaminants we are dealing with, Bi-On Carb OX was considered the most adequate media for the purpose, since it has a number of advantages specially fit for this application:
- Bi-On Carb OX combines a premium quality wood-based activated carbon in conjunction with a proprietary blend of catalytically active inorganic phases, which result in a very high H2S adsorption capacity (80 kg H2S/100 kg media).
- Contrary to other products, Bi-On Carb OX does not convert H2S to sulphuric acid (H2SO4), which may lead to corrosion problems in the equipment and complicate disposal of the spent media.
- Conversely, H2S is catalytically oxidized to sulphur (S) in the active sites on metal oxides. Next, sulphur migrates and builds up in the micropores of the activated carbon phase. Consequently, the metal oxides are available again to oxidize new H2S molecules.
- Bi-On Carb OX also performs very well on other acidic gases such as sulphur dioxide (SO2) and hydrogen chloride (HCl). In addition, it shows a remarkable efficiency at adsorbing any VOCs that may be present in the gas stream.
- Contrary to impregnated carbons, the exceptionally high sulphur loading is not affected even in the presence of high CO2 levels.
- The unusually high ignition temperature (420 ºC) minimizes the risk of bed fire.
Considering these numerous advantages, Bi-On Carb OX is ideal media for use in wastewater treatment plants due to its high H2S removal efficiency, as well as its good performance with other typical foul-smelling contaminants such as methyl mercaptan and some VOCs. Other applications include refineries, industrial sewage plants, pulp and paper plants, pumping stations, sludge holding tanks and composting facilities.
BIOCONSERVACION monitors the performance together with our clients even after the solution has been implemented to observe the media’s performance. Through a laboratory test to verify the remaining life of the media, we can fine tune the media mix to further optimize the process in order to obtain the optimal performance of the installation.
Moreover, Bioconservacion can monitor the evolution of various key process parameters by means of versatile sensors that can be easily placed inside the vessels. With the data collected, Bioconservacion is able to adapt and optimize once again the process for each specific installation. Providing this service strengthens the relationship between the client and Bioconservacion, which can only result in improvements in process and performance.