The work of the plant has 6 - 8 phases, the quantity of which depends on the mode of the work of the plant.
The sewage comes through the grate where the rough rubbish is held. After that the sewage flows into the accepting container-denitrificator (ACD), which works as an SBR-reactor, as an accumulating space for the irregular inflow of the sewage, and as a first-stage denitrificator. It contains the self-cleaning non-rusting grates with double-side barbotage for upholding the rough rubbish, the aerating and mixing systems, the self-cleaning level sensing elements, and the pumps, that pump water into SBR-1. The fresh sewage is mixed here with returnable active sludge from the SBR-3, which contains the nitrites and nitrates. During the mixing mode the process of denitirification takes place and it has a double effect: the denitrification with the deliverance of gaseous nitrogen into the atmosphere and the oxidation of the organic pollutants of the fresh sewage with the oxygen of the nitrates and nitrites. The concentration of active sludge here is always constant due to the level of pumping of the previously cleaned sewage. The pumps, that pump the mixture into the SBR-1 after sedimentation in ACD, pump out the surplus active sludge from ACD at the same time. Changing the height of the pumping level one can regulate the necessary concentration of the active sludge in ACD.
The previously cleared sewage from ACD is pumped into the SBR-1. The SBR-1 is hydraulically connected with SBR-2 by an opening. The aeration in SBR-1 and SBR-2 is periodically interrupted according to the program, and the circulation of the mixture of sewage and active sludge is happening all the time. The second stage of denitrification takes place in SBR-1 during the mixing. As the process of nitrification takes place in the SBR-2, and the returnable active sludge from SBR-2 contains enough of the nitrites and nitrates, and there is still light organic in SBR-1. The denitrification can be more deep when the aeration elements are in the mixing mode - when less air is given for aerating. In this case the denitrification in SBR-1 will take place even when there is aeration in SBR-2, that is to say during all the process of purification. After these reactors the sewage is pumped by the controlled airlifts into SBR-3, they also remove scum in such a way that the microorganisms in SBR-3 are not exposed to the negative effect of the detergents. While the controlled airlifts are pumping the sewage into the third SBR reactor, the recirculation of the returnable active sludge is performed into the SBR-1 and ACD. The SBR-3 works as an aerotank at first, where the processes of hard organic oxidation and the second stage of nitrification take place. After switching off the aeration and the airlifts, it starts acting as a secondary sedimentation tank. The aeration, sedimentation and the pumping out of cleared sewage by the controlled siphon into biofilter-thin-layer sedimentation tank (BFTST), and also the pumping out of the surplus active sludge into the stabilization container with further (after stabilization) dewatering take place. During the aeration of SBR-3 the aeration of central part of the filling of the biofilter takes place, this results in the airlift effect in the cells of the filling , which leads to the recirculation of cleared sewage: in the cells, where air comes, the water moves upwards, and in the cells, where air doesn't come, the water flows down. The plastic filling of the biofilter is covered with a biological layer, and only the part where air reaches works for oxidation (continues to oxydate the hard organic substances and provides the third stage of nitrification), and the cells, where air doesn't reach, provide the third stage of denitrification. The cleared sewage from the third reactor comes to the lower part of BFTST, after the aeration, the sedimentation and the surplus sludge removal is stopped. The sewage cleared in previous cycle in BFTST is displaced by the sewage from SBR-3, and it is moving upwards through the cells of plastic filling, that now starts working as a thin-layer sedimentation tank. This provides the effect of weigh removal five times higher than during the classical sedimentation (literature data and our own experience). The replaced sewage flows into the contact reservoir, where their desinfection takes place. In its turn this water replaces the sewage, that was there before, and makes it outflow from the station.
The display of the block of control of the plants from 10 m3 to 1000 m3 a day shows such parametres as:
- The total time of work of the ACD pump, counting from the first start (hours);
- The quantity of times the clear water was pumped out;
- The quantity of times the clear water was pumped out per week;
- The total quantity of times the cleare water was pumped out from the first start;
- The total time of the plant work;
- The counter of the times excessive sludge was pumped out and the time of pumping;
- The time of switching of the siphon and clear water valves;
- The time of pumping out of the sediment from the BFTST and contact reservoir;
- The time of metering pump's work;
- The sedimentation time;
- The emergency switching of the ACD pumps and so on.
All the parametres of work of the BIOTAL plant can be observed, and changed through the controller program if necessary.
As the composition and the inflow dynamics of sewage differ for each LSTP, the service group can easily correct the work of the plant and change the parametres of its work. This can also be done via modem connection.
The standard programs of BIOTAL plants are made for household sewage, so there is no need to change them, such necessity can only appear when the complex sewage treatment of both household and industrial sewage is performed and also during the volley inflows of sewage, that exceed the projected productivity.
BIOTAL plants from 1,5 to 6 m3 per day
The technology of BIOTAL plants from 1,5 to 6 m3 per day is placed in one cylindrical container and it is a little simplier, however it still solves all the necessary tasks. It is 7-stage, doublesludge system, with 3-planimetric recirculation of the returnable active sludge, that works according to one of 6 programs, to which it switches automatically depending on the quantity of inflowing sewage.
The plant BIOTAL from 1,5 to 6 m3 per day represents a cylindric plastic container, which is separated into the purification zones by partitions. It includes 7 zones of waste-water treatment: 1. The net for the rough rubbish removal. 2. SBR-reactor of first stage. 3. SBR-reactor of second stage. 4. SBR-reactor of third stage. 5. The aerated biological filter. 7. Thin-layer sedimentation tank. 8. The accumulating space for cleared sewage-contact reservoir; and two zones of surplus active sludge processing: 9. The aerobic active sludge stabilizer. 10. The dewatering block.
The sewage inflows into the accepting container, which represents a large non-corrosive net, where the aeration element, that makes small the rough rubbish, is installed. There is an aeration element under this net, it provides the aeration of SBR-1 and outer aeration of the net. The double-side barbotage of the net is taking place, which helps to make the rough rubbish smaller and prevents the cluttering of the net. The water deprived of rough rubbish flows down into the SBR-1, where the returnable active sludge from the SBR-3 and SBR-2 comes. In the first reactor the water is partially cleared, being exposed to the repeated processes of aeration, mixing and sedimentation with the lack of oxygen, thanks to which the process of denitrification takes place (the nitrites and nitrates come with the returnable active sludge from SBR-2 and SBR-3, and the light organic substances that come with fresh sewage). After the SBR-1 the sewage flows into SBR-2, where the scum is removed by the reverse airlifts, which helps to avoid the influence of detergents over the microorganisms in SBR-3. Just as in SBR-1, the sludge mixture is exposed to repeated processes of aeration, mixing and sedimentation. As over 50% of organic substances is oxydated in SBR-1, the nitrification process starts in SBR-2 together with decomposition of organic substances. As the quantity of organic substances decreases, the process of nitrification starts to dominate. The partly cleared sewage from SBR-2 is pumped into the SBR-3 by the reverse airlifts.
The technology scheme of BIOTAL plants from 1,5 to 6 m3 per day.
The oxidation of hard organic substances and nitrification takes place in SBR-3. The conditions that are created for nitrification provide the oxidation of ammonia nitrogen to the nitrites (reduction-oxidation potential less than 100), which allows to have a faster and more effective denitrification in SBR-1, because the chain of reduction of the nitrites to the gaseous nitrogen is shorter comparing to nitrates. The sewage is exposed to aeration with further sedimentation in SBR-3, and the cleared sewage is removed by the controlled siphon into the biological filter. Before the cleared sewage is pumped out, the pumping of the surplus active sludge from SBR-3 into the aerobic sludge stabilization container takes place, and the pumping out of stabilized active sludge into the dewatering block. After the cycle of sedimentation in SBR-3 is over, the pumping out of the cleared water and its delivery into the biological filter takes place, where there is the water that was cleared in the previous cycle of purification. While the new portion of sewage comes to BFTST, it replaces the water that was purified here before, and as the aeration is off at this moment, the plastic filling begins to play the role not of a biological filter, but a of thin-layer sedimentation tank, which effectively holds the smallest weigh. The final result of this is the outflowing cleared sewage. In case that it is necessary to pump out the cleared sewage with a pump, it is set over the plastic filling of the biological filter, where the cleared water is accumulated.
The BIOTAL waste-water treatment plant (upside view)
Irrespective of the high technological level of the BIOTAL plant, and also the use of the components of the leading world manufacturers, full automatization and a significant warranty term, the price of BIOTAL is not higher than the price of most plants presented at the market, that cannot solve the tasks BIOTAL easily copes with, but sometimes even lower. This became possible thanks to the serial production, manufacturing and technology modernization.
| The sawage water treatment plant BIOTAL |
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Dr. TETERJA ALEXANDER