Liquid purification or separation – Recirculation
Reexamination Certificate
2000-06-16
2001-04-17
Lithgow, Thomas M. (Department: 1724)
Liquid purification or separation
Recirculation
C210S195300, C210S197000, C210S151000, C210S201000, C210S202000, C210S205000, C210S198100, C210S748080, C210S603000, C210S610000, C210S615000
Reexamination Certificate
active
06217759
ABSTRACT:
TECHNOLOGICAL SPHERE
The invention belongs to the treatment of industrial sewage, more precisely to the installation for biochemical treatment of high-concentrated sewage with the organic impurity concentration of up to 10000 mg/l BOD
20
and suspended matters up to 5000 mg/l; it can be applied for the purification of the sewage produced by sugar-houses, yeast factories, meat-preserving and fish factories, those enterprises referred to chemical and pharmaceutical industries.
Besides, this invention may also be used for public services and technological microbiology.
PREVIOUS LEVEL OF TECHNOLOGY
For the treatment of the sewage showing high content of organic impurities, traditionally applied are step-like purification schemes which include primary settlers, biofilters with plastic charge in them, aeration tanks and secondary settlers. At the first stage, the biofilters, alongside with the settling, also provide BOD (biochemical oxygen demand) reduction by 50-70%. The second stage is performed in aerotanks working in the mode of average or low loads upon sludge and provides the purification effect (after settling) of up to 95-98%. In case there are fats and emulsified matters in the sewage, the technological purification scheme is complemented by flotation units.
The drawback of the above schemes is their operational complexity due to the application of various pumps and compressors in the technological processes. To run off the foam, scraper-type devices are installed in the flotation units. Besides, in order to provide environmentally clean operation of the plant, it is necessary to install fans sucking off and feeding to the decontaminating installations, the air used for biochemical processes. The availability of different types of machinery and low oxygen utilisation factor in aeration tanks stipulate high energy consumption during sewage purification.
Well known is a combined device for biochemical sewage treatment, the one containing a biofilter located above the settler aerotank with the pipes providing jet aeration of the liquid and attached to a collecting tray of the biofilter, a mixing chamber and a circulating pump (RU No. 1020379 CO02F3/02, 1981). The operation principle of the device is as follows: the sewage, after being preliminarily treated (i.e. after the removal of rough dispersive impurities), is driven to the mixing chamber where the sludge mixture from the settler aerotank is also directed under hydrostatic pressure. Further on, the mixture of sewage and sludge is circulating with the help of the pump through the biofilter, feeding pipes and settler aerotank. Biochemical oxidation of the impurities is performed due to the biocenosis attached to the biofilter charge, as well as by microorganisms of the active sludge contained within the settler aerotank. While being irrigated and driven through the biofilter, the sludge mixture is saturated with air oxygen. Additional saturation of the liquid with oxygen inside the aeration tank and the stirring of its contents are performed due to the process of air involvement in the feeding pipes, movement of gas-and-liquid flows and during the air bubble upward floating. The merits of the above device are as follows: high sewage purification level due to the combination of oxidation and sorption potentials of the biofilter biocenosis and the aerotank active sludge; application of a simple low-pressure pump as the major equipment unit; low power consumption reaching 0.5 kWt h/kg BOD.
On the other hand, the application of the above device for concentrated sewage treatment in a one-step design is restricted by the purification effect, i.e. the purification level, in what concerns the residual impurities BOD and the suspended matters of up to 15 mg/l, may be achieved only in case of the organic impurity contents in the initial water of up to 1000 mg/l and the suspended matters of up to 500 mg/l BOD.
Besides that, to provide oxidation of the sewage nitrogen compounds it is necessary to significantly enlarge the size of the combined device and the deep sewage tertiary treatment installation, e.g. of a bioreactor with artificial charge in it.
Known is the biostimulating effect of a He—Ne laser (HNL) upon the activation of bioenergetic processes in microbe cells (Voskonyan K. Sh., Simonyan N. V. et. al. The Dependence of the He—Ne Laser Radioprotective Effect Produced upon the Bacteria Cells on the interval between the Two Kinds of Radiation. Radibiologiya - 1987, v.27, No.5, pp. 708-711). Experiments have been undertaken on the effect of 633 nm long wave HNL upon the biological activity of the active microflora of sludge. The total amount of bacteria raised 3-3.5 times after 1 hour in case of 15 second to 5 minute long radiation. Meanwhile the NO
3
concentration grew 2.5 times, and the NH
4
+
grew 2 times.
The cone-like shape of the settler aerotank inside a prototype casing would have been expedient provided the capacity range of the plant reached 1000 m
3
/day. In the event of higher capacity, due to their angles making 50°, the construction height of the settler aerotanks is significantly increased, while in case the bottom is designed to have a number of cone pits in it, and the sludge is driven out of each of those pits, the adjustment of the hydrodynamic mode of the sludge mixture circulation is complexified.
The other factor limiting the application of the device, is the unavailability of charge materials which would meet the following requirements to the device operation:
the developed biocenosis should be fixed on the charge surface, this biocenosis, alongside sorption and oxidation of the organic impurities, performing nitrification and denitrification;
the charge should not be silted during the irrigation with the sewage whose sludge solid matter concentration reaches 7 g/l.
The efficiency of the biofilter charge operation depends on the regularity of irrigation of its surface. On the other hand, the existing sprinkler systems fail to provide satisfactory regularity of irrigation under constant pressure inside the distribution line since the liquid drops are mainly fed within the radial range of 0.2-0.3 m.
Known is the application, within the technological designs with aeration installation, of biocoagulators destined to partially extract sewage impurities (see the book: S. V. Yakovlev, Ya. A. Karelin et. al. Canalisation.—Moscow. Stroyizdat. 1976. Pp. 260-262).
It seems expedient, in case the sewage impurities show concentration higher than 2000 mg/l BOD, to reduce, with the help of the second biocoagulation stage, the impurities content to 80% and oxidise the caught matters in a fermenter whose design is analogous to that of the combined device. The process of destruction of the impurities in the above unit may be performed with high loads upon the active biomass. The processes of the impurities oxidation should be activated by way of radiation of the sludge mixture with He—Ne lasers. To oxidise the rest of the impurities, one should apply a biofilter with a sunk and unsunk charge, a combined device and deep tertiary treatment of sewage. With the aim of destruction of the sewage nitrogen compounds, the process is performed with average and low loads upon the active biomass and with the laser biostimulation application. In order to efficiently mix the sewage and sludge, to supply the biochemical processes with oxygen and displace utilised air for its further disinfection, it seems expedient to apply water jet aerators within biocoagulators, biofilter and bioreactor for tertiary sewage treatment.
In order to reduce the plant height, the fermentor and combined device bottom may be flat, while to efficiently stir the sludge mixture, it would be reasonable to use definite location of the aeration system feeding pipes and apply devices preventing sludge bedding.
The oxidising power of the plant can be enhanced due to the new configurations of the charge materials. At the same time, the biofilter charge should favour the fixing of the developed biocenosis to the surface and, simultaneously, exclude sludge bedding
Gordeev-Gavrikov Vladimir Konstantinovich
Klimukhin Vladimir Dmitrievich
Kolesnikov Vladimir Petrovich
Collard & Roe P.C.
Kolesnikov Vladimir Petrovich
Lithgow Thomas M.
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