The basic treatment process:
The basic treatment technology in “Asahi Jokaso Family” and “Asahi Jokaso Industry” consists of a well balanced combination of the processes of denitrification and nitrification, both a part of the biological treatment stage. The biological treatment of water is a completely natural process, based on the self-cleaning which occurs in lakes, rivers and other water basins with the help of the microflora living in them. In WWTPs, this process of dissolving organic matter occurs much more intensively than in nature, because there are more favorable conditions for the developing of said microflora.
Biological treatment can be combined with filter technology like micro- and ultrafiltration, in order to non-chemically disinfect the treated water and allow its re-use for non-potable purposes. These two filter technologies are realized through special membranes, which have specific pore size: 0.01 - 12 μm for microfiltration and 0.002 - 0.03 μm for ultrafiltration ones. The membranes contain all substances and bacteria with a size, bigger than the size of the pores, letting only the water through.
To learn more about the different treatment stages, please click on the corresponding rectangle:
Primary sedimentation is one of the most common mechanical (primary) treatment methods and it allows separation of floating material and heavy solids from the liquid waste. Typically, in WWTPs the wastewater first enters a primary sedimentation chamber, in which the lighter substances, such as grease and oils, rise to the surface while the heavy substances settle as sludge. As it you can see in the above flowsheet, our products are usually designed to have not one, but two separate sedimentation chambers. This achieves a much better quality of the wastewater for the next step of the treatment process, as well as provides a big capacity for sludge accumulation, eliminating the need for often removal.
As we already mentioned, denitrification, together with nitrification, are a part of biological (secondary) treatment, where dissolved organic matter is removed from the wastewater. In the case of “Asahi Jokaso”, after the wastewater undergoes a two-step sedimentation, it is then introduced to an anaerobic chamber. Here that the process of denitrification occurs, which means that the dissolved nitrate is reduced and ultimately molecular nitrogen (ammonium) is produced. This process is facilitated in an anoxic environment by anaerobic bacteria, accumulated on the plastic media in the said chamber. The plastic media, used in our WWTPs, has a specific shape, which provides a very wide surface for the accumulation of biomass, as well as prevents clogging.
Nitrification is the reverse process of denitrification - the biological oxidation of ammonia or ammonium to nitrite followed by the oxidation of the nitrite to nitrate. Or said more simply - the organic matter is consumed by microorganisms as food, who then convert it to carbon dioxide, water, and energy. Opposite to the denitrification chamber, here the media is in an aerobic environment (i.e. there is oxygen dissolved in the water). The oxygen is necessary for the bacteria to oxidize the organic matter, else said bacteria would not receive enough energy to survive. Therefore, the quantity of dissolved oxygen is vital for the efficiency of the treatment process in the nitrification chambers; they need to be constantly and thoroughly aerated. This is usually done by aeration pipes, placed in said chambers and connected to a blower. In the basic “Asahi Jokaso” the wastewater is consequently introduced to two separate aeration chambers, which allows for an extreme reducement of the organic matter, resulting in very low biological oxygen demand ( or BOD) value of the effluent. *BOD is the amount of dissolved oxygen needed by aerobic bacteria to break down organic material present over a given time period and is universally used as a measure for the level of pollution of wastewater. The lower its value is, the cleaner is the water.
While exiting the aeration chamber, the treated water is not yet separated from the active sludge. Therefore, the next step in the treatment process is allowing the sedimentation of said sludge. This happens in the secondary sedimentation chamber, where, after the sludge has settled thanks to gravity, it is returned to the aeration chamber. Only the treated water is introduced to the next and last chamber.
Typically, this is the last step of the wastewater treatment process. In the disinfection chamber, the bacteria and microbes in the water are killed by dissolving in it an optimal dose of chlorine. The effluent can then be stored and safely re-used for irrigation, car-washing, artificial ponds etc. As it was already mentioned, a modern technological solution for water disinfection without the use of chlorine and other chemical substances is the membrane bioreactor, which we implement at our industrial wastewater plants. This step is optional and we include in in the design of our WWTPs according to the client`s individual needs.
Depending on the qualities of a given facility` s wastewater and the client`s wishes, it is possible to introduce additional (one or more) treatment steps, in order to comply with all of the legal requirements and regulations for discharge of the effluent in rivers/lakes , or for water re-use. Some of the optional steps that we offer are: membrane bioreactors, ultrafiltration modules, RO modules, etc.
AN Aqua Network Ltd. is a subsidiary company of the Japanese SWATO Inc. , which specializes in custom design of compact wastewater treatment plants for domestic and industrial wastewater, as well as other products and services from the field of water treatment. Our company`s policy is completely in line with the traditional Japanese practices for strict quality control, long-term maintenance and prioritization of the custumer`s needs and wishes. At the same time, by incorporating the latest technologies in the field of water treatment, AN Aqua Network strives to always provide its clients the most fitting and reasonable solution to their problems.