Why is water purification a necessity?
Factories and urban facilities are responsible for water pollution. As this is a limit resource, it is essential today to purify it. Thus, more people will be able to benefit from it, without risk to health.
In France, Wastewater Treatment Stations (STEP) must comply with increasingly drastic national and European regulations. However, through negligence, but also for fear of too much investment, many sites do not treat their wastewater as they should. It is a risk for them because they can be sanction until the activity is close, but it is also a danger for the environment and the population. In order to generalize water purification and offer solutions that are both efficient and economical, Industrad Group, a specialist in industrial gases, has been involve in the treatment of effluents for more than 30 years. Perfectly suite to the current challenges of wastewater treatment, regardless of the sector concern, these tailor-made responses are use today by many companies and communities.
The main stages of water purification
Wastewater treatment plants can intervene in the treatment of wastewater, or in the purification of water.By definition, the wastewater treatment plant makes it possible to eliminate water pollution (domestic, industrial or rainwater) in order to to be able to reject it in a natural environment (lake, river, sea) or to reuse it. The vocation of a WWTP is to “upgrade” the quality of the water so that it meets the environmental standards in force. In a wastewater treatment plant, wastewater treatment is carry out in three distinct stages, before discharge into the natural environment. These are pre-treatments, primary treatments and secondary treatments.
The pre-treatments
The purpose of the pre-treatments is to remove suspend solids. This can do by screening, the most common process for retaining large waste, thanks to a screen filtering the wastewater. The purpose of sand removal is to remove sand and gravel, in particular, through the sedimentation process. It consists of letting the water stand while the particles settle at the bottom of the basin. Finally, the degreasing method aims to get rid of the fat contain in the water by flotation. The air is inject at the bottom of the tank and the fats rise naturally to the surface.
Primary treatments
Primary treatments are essentially physical or physicochemical sanitation processes equivalent to settling. This eliminates all the solid pollution present in the water and reduces by 30 to 40%. BOD (biological oxygen demand ) and COD (chemical oxygen demand). The implementation of this primary treatment will considerably reduce the amount of organic matter to treat subsequently. However, in stations using the activate sludge system, this phase is unnecessary because settling is de facto include in the sludge treatment.
Secondary treatments
The purpose of secondary treatment is to treat the last organic substances present in the water, via a biological solution. Organic matter is again target in order to reduce it to the strict minimum. Carbon and nitrogen are the main gases use in the biological treatment of wastewater. The devices for treating activate sludge depend on the size of the plant, the environmental needs, and the nature of the project. Secondary physicochemical treatments, for their part, eliminate phosphorus. These sanitation networks are suitable for structures whose discharges are carry out in a so-call “sensitive” environment. The use of different technologies in the station is then possible: filtration, membranes, chemical and / or biological treatment.
How is gas use in the water purification process?
The era of acids and other polluting products is behind us. Fortunately, the gases are also use for the purification of wastewater, regardless of the treatment phase.
For example, pure oxygen is fed into biological treatment facilities in order to avoid foaming and odors. It also allows sanitation stations to avoid having to resort to expansion work. Indeed, a small structure under oxygen will treat the water as much as a large conventional under air. For its part, CO2 makes it possible in particular to effectively and progressively reduce the pH of wastewater basins: it is the gas of choice for the neutralization of effluents. As for ozone, one of the most powerful oxidizing agents, its main virtue is to eliminate pathogenic organisms or recalcitrant pollutants, in particular micropollutants (pharmaceutical residues, hygiene products), surfactants or inks.
