Wastewater cleaning

Wastewater treatment using SAF technology

In cooperation with the Danish company Sunstone Water Group, a world leader in the field of biological treatment, we are able to offer cutting-edge wastewater treatment systems, using SAF technology (submerged aerated filter).

The development of settlements and the increase in the standards of the population cause pollution of the human environment, among which the most severe form is the pollution of water. Water consumption for various needs is increasing, which causes an increase in the amount of wastewater. This trend of increasing water pollution significantly endangers the human environment. Drinking water is increasingly polluted by wastewater.

Over 30% of drinking water in England contains "used" water. In the drinking water used by Paris the percentage of "reused" water is over 50%, and the Ruhr area (Germany) uses drinking water with a share of about 40% of treated wastewater. The requirements for the quality of discharged water are becoming increasingly strict, which must be met by the technology of its treatment.

The drainage system reacts very sensitively if too much fat gets into it. Unfortunately, it is not always possible to prevent fats and oils from entering the drain with wastewater. Fats consist of solid and soluble substances. Solids settle on the walls of the pipe and cause blockage. In the system fats and oils are changed due to chemical and biological reactions into fatty acids with unpleasant odors. These acids are extremely aggressive and lead to corrosion.

It is different in crafts and industry, where wastewater containing oils and fats is discharged. The application of DIN EN 12 056, DIN EN 752 and DIN 1986-100 is prescribed by the municipal drainage regulations. According to DIN 1986-100, these companies are obliged to carry out drains via grease separators according to DIN 4040-1 and DIN V 4040-2. In this way, drains from the kitchens of restaurants, hotels, resorts (on the highway) and canteens must be equipped with devices for separating fat, regardless of the number of portions of food, which are prepared there daily.

Biological wastewater treatment

The planned biological part consists of nitrification and denitrification pools. In the central reinforced concrete or plastic (PEHD) cylinder of the pool, equalized and finely mechanically purified (deposited) wastewater and active return sludge are supplied by pressure pipelines. In this pool, anoxic conditions are established very quickly. Bacteria of activated sludge responsible for denitrification begin to consume oxygen from the present nitrates in equalized raw wastewater and sludge, whereby nitrogen is released in the gaseous state and with increased mixing of the contents in the cylinder is extinguished in the atmosphere, ie. denitrification of nitrogen compounds is performed.

All of the above is done through aerobic microorganisms (activated sludge) with the artificial introduction of the required amount of oxygen using aeration branches with modern membrane aerators. The required amount of oxygen is introduced by blowing compressed air produced by the blowers located in the compressor station. The final separation of the treated wastewater and sludge is done in the remaining outer ring of the settling tank in which a predominantly horizontal flow is established towards the overflow cantilever grooves on the outer rim of the settling tank.

The principle of operation of a submerged aerated filter (SAF) is that previously treated or placed wastewater passes through a filter layer where a bacterial culture called a biofilm degrades the dissolved organic pollution. Also, part of the suspended solids and colloids is absorbed by the biofilm and thus removed from the wastewater.

Among other things, submerged filters have the following favorable characteristics:

• stable operation
• easy handling (also used for detached housing units)
• unlike suspended biomass processes, they do not require sludge return or recirculation

Fixed layers are submerged biofilm reactors in which the carrier or solid material is located below the water surface (submerged). In fixed support bearings, the filling material can be a structured module or a bulk material, but the assumption is that it must be fixed without movement, as in the usual layer of bacteria. These can be called Submerged Aerial Filter (SAF) biofilm processes. Excess biofilm is continuously separated by erosion, so final deposition or filtration is required. However, washing the filter is not necessary.

In most cases, it is considered good practice for treatment plants to consist of several units with ventilation layers, so that the reaction unit is divided into several phases. The development and rise of this process began in the 80's, its development was aimed at improving the performance of filters.

They are currently used as:

• pretreatment, mainly from heavy industrial wastewater
• secondary treatment, with or without nitrification
• tertiary nitrification
• simultaneous nitrification / denitrification

The advantages of SAF technology over competing SBR, SBBR, MBR and MBBR are lower fabrication and installation costs, very low power consumption required for oxygen input and final filtration, as well as smaller dimensions of the entire system.

When it comes to lower prices, there is less price difference between SAF and competing technologies in small systems, but with increasing volume and flow of the entire system, the price difference grows by an almost exponential difference in favor of SBR technology.

For more details on SAF technology, see our SAF study