Autonomous sewerage for a private house

Project summary

Rationale for the production of Biological Treatment Plants (BSS)

domestic waste water.

The last decades have been characterized by a change in the attitude of society towards environmental pollution. It is obvious that not only industry, but also human everyday life causes significant damage to the environment.

One of the types of environmental pollution by private households is soil pollution with domestic waste water (DSS). In the post-Soviet space, the traditional way of disposal of BSW is cesspools, which have many disadvantages, including:

• Non-environmental friendliness. (poisoning of the soil around the pit).
• The need for their constant pumping. (expensive and foul-smelling procedure).
• The need for access roads for sewage trucks at the site.

Only 0.5% of private households in Ukraine use biological treatment plants. The main reason for such a small number is the lack of awareness of the population about the existence of another civilized way.

In many countries, cesspools are prohibited by law, and Ukraine, in its path to harmonization of national legislation with European norms, will do the same in the near future. The Ministry of Regional Development, Construction and Housing and Communal Services of Ukraine has already prepared a draft law "On wastewater disposal", which will tighten these standards.

The listed facts allow us to make an assumption about the high capacity of the market and the prospects of this business.

Modern SBO is a compact sewage treatment plant lowered into the ground made of materials resistant to corrosion. They are actively developing bacteria that cleanse household waste. These installations provide a high degree of cleaning (up to 98%), including cleaning from such contaminants as feces, toilet paper, detergents from washing machines and dishwashers, small food residues, etc. At the exit from them, industrial water is formed, which, according to sanitary standards, is permissible to be discharged into drainage ditches, reservoirs, etc. Usually they are connected to the "filtration field" in the area where it is absorbed into the soil.

It is not allowed to discharge aggressive chemicals in the SBO for cleaning sewer blockages, building mixtures and adhesives, paints, cigarette butts, reusable napkins, synthetic and rubber products, including personal hygiene products.

Biological Treatment Stations are divided into two groups.

In the first group, the process of domestic waste water treatment is carried out thanks to the forced air supply by a compressor in the station section. As a result, wastewater is saturated with oxygen, which allows aerobic bacteria to actively develop in them, which additionally purify wastewater to a level of 98%. Further, the purified water flows by gravity into the soil and is absorbed into it.

The disadvantages of this technology are:

• The complexity of the design (pipes, splitters, valves, many non-standard sections, etc.).
• Volatility. In the event of a compressor failure or lack of electricity, aerobic bacteria in the effluent die within two hours and the process of aerobic purification of the effluent stops. Depending on the duration of the downtime, the time it takes to restore the required amount of aerobic bacteria in the effluent can take up to a week. Accordingly, all this time, under-treated water will enter the filtration fields or other receivers and flood them.

In another group, SBO is a septic tank with a bioreactor. Inside the bioreactor there is a bio-load, which is an elastic or solid structure, on the surface of which a colony of aerobic bacteria - a biofilm - grows and actively develops.

Waste water, purified by a septic tank up to 65%, rises from the septic tank with the help of a submersible pump and is constantly sprayed inside the bioreactor. Flowing through the biofuel, water is drained by gravity back into the septic tank chamber with a submersible pump. Thanks to this vicious circle, a constant circulation of waste water is ensured. The biofilm formed on the surface of the biofuel uses the impurities dissolved in the flowing water as its food and thus purifies it up to 98%. Further, the purified water flows into the soil and is absorbed into it.

The advantage of the second technology is its simplicity of design.

In the event of a pump breakdown or a lack of electricity, aerobic bacteria on the biofuel continue to live for up to two weeks, while the process of purifying wastewater in a septic tank does not stop, but simply drops to 65% as in a conventional septic tank. After replacing the pump or the appearance of electricity, the cleaning process resumes to the required degree within one to two hours, in contrast to systems with compressors, where recovery to normal levels can take up to 1 week.

Thus, I found the second technology more attractive and promising.

Having studied the products of companies using purification technology in a bioreactor, I identified the following design flaws:

1. The stations are completely plastic, and in order to prevent them from floating or changing their position in the ground, they require anchoring in case of a sudden or permanent high groundwater level.
2. The body of the station, in most cases, is welded by hand, and as a consequence of the "human factor" these are shortcomings that appear over time.
3. Bioburdens used by some companies are elastic and multi-layered, during operation they are compressed and create an "air shadow". At the same time, the lower layers of biofuel, deprived of air access, cease to perform their function, and as a result, the quality of wastewater treatment decreases. In this regard, they require flushing and re-laying every 6 months to maintain the required degree of effluent purification, in order to avoid flooding of filtration fields.

I propose a combined station design in which:

• The septic tank is made from standard concrete rings, and this eliminates the problem of floating or changing the position of the station in the ground.
• The bioreactor is made of polyethylene by hot molding at specialized enterprises and is a monolithic structure without seams and joints. This technology ensures high quality and completely eliminates the influence of the "human factor".

The plastic bioreactor is mounted on the concrete rings from above and does not need to be fixed. Another advantage of this design is that, if necessary, which is extremely rare, the bioreactor can be easily removed and direct access to the septic tank is opened. This is not possible in fully plastic structures.

In addition, I have developed and patented the design of a cassette-type biofuel, which has the following unique properties:

• This biofuel does not require regular maintenance
• Provides 100% air access to the entire active surface of the biofuel
• Has the highest, among analogues, the area of the active surface of the biofuel for the formation of biofilm. (320 m2 in one m3).

These undeniable advantages allow us to guarantee a consistently high level of final (aerobic) treatment of domestic wastewater for private households.

All of the above allows us to conclude that it is possible to create an innovative high-performance business in a segment with little competition and huge market potential.