sewage water purification plants     

The system for waste water purification can be estimated with many features, but the main ones are these (which no expert can deny):

 

1. The level of solving the problem of rough rubbish removal

 

2. The regulation of air agitation and the rate of sludge mixture circulation between the biological reactors, which depends on the volume of the inflowing sewage.

 

3. Automatic maintaining of the necessary activated sludge concentration in the system by removing the surplus sludge (at least once every 1-7 days, depending on the productivity and the load), aerobic sludge stabilization and dewatering

 

Some clients adore to listen to the tales of some small SWTP, that tell that the surplus sludge can be removed from their plants once or twice a year and so on.

 

We will compare the BIOTAL plant to other plants using the calculations, not the tales, even if those tales are sweet, like “Their plant is too complicated which is why it is not reliable”, “Our plant doesn't require any service at all”,  "There is no surplus sludge in our plants at all" etc.

 

Let us see how these problems are solved in the BIOTAL plant and in the plants of other manufacturers.

 

The BIOTAL plant has a non-rusting net of a significant volume (more than 100 l) with openings that have 3 mm in diameter. The net has also inner and outer barbotage for disintegrating the rough rubbish inside the net, and the fixed cover, which prevents the outflowing of rough rubbish into the reactors in case of an untimely service.

 

When we started using the net, we solved a few problems at once: we protected the plant from the rough rubbish clogging; the rough rubbish inside the net plays the role of the biological filter filling; as the air is agitated into the rough rubbish in the net, it is gradually washed from the faeces and they serve as a nutrition source for the microorganisms of activated sludge during the periods when no sewage water comes into the plant.

 

Other plants either don't have the net for rough rubbish removal at all, or have a comparatively small basket (about 20 l) with big openings (about 20 mm). The nets have no covers. It is not difficult to guess what it may cause. If there is no rough rubbish removal net, the accepting container will be clogged with trash very soon, the rough rubbish will stay on the bottom of the container, it will be quite difficult to remove it from there, ant it will go into other purification zones of the plant, which will caust the airlifts clogging and the plant failure.

 

The plastic basket with big openings for rough rubbish removal will not help significantly, because all the rough rubbish with the size less than 20 mm will come into the plant with all the consequences. When the plastic basket will be filled with rough rubbish, it will pass into the reactors and it will lead to clogging the airlifts and the plant failure. As soon as this basket gets filled with the rough rubbish, it will pass into the reactors and it would lead to the plant failure.

 

Certainly, the non-rusting net of the big diameter costs a lot, but we also have quality and reliability as our priorities.

 

The BIOTAL plant is yet the only one that has automatic power regulation, that depends on the volume of the sewage that inflows, the plant switches into one of five programs automatically. This solves a few problems at once:

 

The electric energy is saved, the resource of compressors and magnetic valves work is saved, the necessary concentration of oxygen is maintained in the reactors (the less sewage water comes into the plant – the less time the compressors work and vice versa). Thanks to this the plant copes with the sewage water with the increased organic substances concentration, and when the fresh sewage water is not available the plant decreases the activity of the microorganisms of the activated sludge by decreasing the air agitation, which in complex allows to provide normal work of the system even during the long-term absence of fresh sewage water.

 

Other plants do not solve this problems. At best some plants have a manual mode of regulation the time of compressor work, and other plants switch into the economic mode at complete absence of fresh sewage, but neither of the plants can regulate the air agitation and the recirculation rate according to the volume of the sewage water that comes to the plant. 

 

It is well-known that the activated sludge is formed in volumes defined by formula (see the article Why BIOTAL?). If one counts how much sludge is formed for one inhabitant, he'll get the result of 7-8 l of sludge mixture from the activation zone (99,5% humidity), which corresponds to 1,5 l of the settled sludge (98 % humidity) or about 0,1 kg of dewatered (about 92% humidity) sludge from the dewatering bag per day. To maintain the necessary concentration of activated sludge in the plant (about 4 – 5 g/l), one should constantly remove all the surplus sludge from the system (at least once a week).

 

The necessary activated sludge concentration is automatically maintained in the BIOTAL plants, the surplus sludge is not only removed automatically, it is also stabillized in the aerobic stabillizer automatically to provide better dewatering in the dewatering bag; meanwhile the volume of the dewatered sludge is decreased 15-20 times. Our plant for the private house has dewatering bags, and each bag can accumulate 90 l of the dewatered sludge; this is 1800 l of the settled sludge, that is to say that if 6 people live in the house, the bag will be filled after three months. As the calculations were made for the regular load and they do not take into consideration the vacations and so on, the bag is filled approximately after 6 months. The statement of some manufacturers that their plants require sludge removal once or twice a year having a 200 l sludge accumulating container is false. As one should remove 6 * 1,5 = 9 l of sludge (98% humidity) per day from the plant for 6 people, that is to say that the sludge container with 200 l volume will be filled during 200 : 9 = 20 days. After 20 days not the sludge water, but the sludge itself will go back to the plant from the sludge container. The sludge concentration in the plant will increase and it will cause the decreasing of the dissolved oxygen concentration in the activation zone, which leads to the anaerobic process with the hydrogen sulfide liberation which causes the malodor. The purification will certainly stop, and the plant will fail.  Other manufacturers tell even more – they state that sludge doesn't need to be removed from the system regularly, and that it is enough to pump it out with the sewer machine once or twice a year. No comments are required here, as after the month such plant will turn into a malodorous septic tank.

 

 BIOTAL and other technologies (comparison of the small WWTP, productivity 1,5 – 6 cubic metres per day

 

	Feature	BIOTAL	Other small WWTP
1	Big non-rusting net for rough rubbish removal with double-side barbotage	YES	NO
2	Automatic power regulation at sewage water volume change	YES	NO
3	Aerobic surplus sludge stabilization and dewatering	YES	NO
4	Double-sludge system of wastewater purification	Double-sludge	Single-sludge
5	Seven-stages wastewater treatment system	YES	Not more than 4 stages

 

That is to say,

 

1)      The BIOTAL plant is the only plant in European experience that has a seven-stage purification, which includes the circulation biological sand filter, which allows to achieve the 99% water purification.

2)      The plant has the automatic 5-program power regulation that depends on the quantity of wastewater that is accepted by the plant. It provides the economy of electric energy, the resource of the equipment and it also balances the technological processes.

3)      Automatic surplus sludge removal and its aerobic stabilization and dewatering are provided by the technology, and this module is situated inside the plant.

 

Certainly, these are not the only advantages of the BIOTAL technology, you can get acquainted with them more thoroughly in the “Advantages of the BIOTAL plants” section of our website.