WO1984001362A1

WO1984001362A1 - Terraced-casketed sewage treating system

Info

Publication number: WO1984001362A1
Application number: PCT/HU1983/000050
Authority: WO
Inventors: Janos Fenyoevari; Gyula Kiraly; Istvan Molnar; Endre Papp
Original assignee: Alkoto Ifjusag Egyesueles
Priority date: 1982-10-06
Filing date: 1983-10-06
Publication date: 1984-04-12
Also published as: HU186132B; EP0123685A1

Abstract

Terraced-casketed sewage treating system for the simultaneous or separate purification of sewages of different origin, such as snifted sewage, dung water, etc., said purification being based on natural biological decomposition. The system itself is characterized in that it consists of caskets (3, 4) connected in series, the majority of which being lined - at least partially - with peat (12) and optionally lined on the bottom with a compacted material, furtheron the system is provided with aerating wheels (5) arranged in the water stream between the single caskets promoting the introduction of oxygen needed for purification, said system being further optionally equipped with scum-traps placed in the caskets (3, 4) and with slowly operating filters (6) for the removal of floating matters.

Description

Terraced-casketed sewage treating system

Technical Field

The invention relates to a terraced-casketed sewage treating system for the simultaneous or separate purification of sewages of different origin, such as snifted sewage, dung water, etc., said purification being based on natural biological decomposition. The system itself is built-up of a plurality of caskets mostly arranged in a terraced formation and having different water-depth and size.

Background Art

In technical literature several methods for sewage treatment based on natural biological decomposition are described, out of which some have been used in practice.

Among others, processes based on biological decomposition are specified in the book having the title "Biological sewage treating system" published in 1973. In the cited book reference is made to the fact that presently in the USA more than 3000, in Canada more than 500 stabilizing lake-systems serving for this purpose are being in operation.

Technical literature deals also with the dimensioning of such lake-systerns, so e. g. examples are given for dimensioning oxidizing lakes in the publication of F. Meinck - H. Stooff, H. Kohlschütter: "Industrie-Abwässer" (Stuttgart, 1968). Further dates are to be found in the book titled "Scieki przemystowe" (author: Bohdan Koziorowski, Warszawa, 1980), discussing first of all purification of industrial sewage and the problems connected thereto.

Technical literature contains several quotations from the works of Goyna, E. F. ; Preul, H. C. and Hills, D. J. , so among others, the following statements:

"According to dates of sources of the German Democratic Republic investment costs of stabilizing lakes amount to 20 to 25 % of those of traditional plants. At the same time, the efficiency of purification equals to - the more it surpasses - that of traditional plants. In the German Democratic Republic a system consisting of three lakes is cleaning a 500 mgBO/₅/1 sewage in the whole year with a BOI-efficiency of 80 to 95 %. The first lake is an anaerobe lake, the second an areated and the third a filter-lake."

"According to Goyna, the majority of the infective bacteria is destroyed in the biological lakes. He proposes that a number of lakes are to be established with different oxidizing conditions. Based on examinations having been performed on ten biological lakes it could be demonstrated that penetration of oligotropics considerably depends on the soil. The farthest traces could be found in a distance of about 60 m from the lake."

"In New-Zealand, in case of an anaerobic lake it could be demonstrated that extent of infiltration amounts to about 1 % of the quantity of the sewage introduced.Infiltrated water contained 0,1 % contamination of all contaminations contained in the raw sewage."

The aim of the present invention is to develop a sewage treating technology and a system for the realization of said technology, the energy requirement of which practical equals to zero, space requirement is less than that of presently used processes based on natural decomposition, and, at the same time, efficiency of purification is higher and simultaneous purification of sewages of different origin becomes possible.

Disclosure of Invention

Essentially, the proposed technology according to the present invention is similar to the purification process applied with the stabilizing lakes, however, the main difference lies in that in accordance with the invention smaller lakes, i. e. caskets are formed in an increased number, to which, as combinative elements, aerating terraces are connected, by the aid of which quantity of oxygen dissolving on the surface can be increased to a multiple value of the usual quantity. At the same time space requirement can be decreased and the efficiency of purification can be further increased.

According to the invention the aim set is achieved by means of a terraced-casketed sewage treating system, which consists of caskets connected in series, the majority covered at least partially with peat and optionally coated on the bottom with a compacted material, said system having been provided with aerating wheels arranged in the water stream of the single terraces promoting the introduction of oxygen needed for purification, as well as means for retaining floating matters and also with slowly operating filters for the removal of suspending substances.

With a preferred embodiment of the sewage treating system according to the present invention the system is composed of at least five caskets in total, partly of a smaller area and with a water-depth of 1,0 to 2,5 m and - compared to the previous ones - of a larger area, with a water-depth of 0,3 to 1,2 m with an aerobic character, all connected in series, to which at least one casket with the character of an aerobic lake, expediently with a water-depth of 2 to 6 m is coupled.

With a preferred embodiment of the water treating system according to the present invention the caskets are arranged in a terrace-like manner in order to promote introduction of air. With a further preferred embodiment of the sewage treating system according to the invention there is provided for at least one aerating wheel driven by the energy of the sewage to be treated.

A further preferred embodiment can be characterized in that in the caskets each, in a depth of 10 to 30 cm at most, traps are arranged for catching the floating matter arriving with the sewage to be treated or formed in course of the process of purification.

The process accordirg to the invention is also serving for realizing the aim set, in course of which for the removal of the living beings, in particular algae, as a slowly operating filter coarse-granular sand is used, thereafter, in compliance with prevailing requirements, in order to decrease the concentration of certain material after-filtration on zeolite is performed. With a preferred mode of performance of the process according to the invention decrease of the number of bacteria, selection, adsorption of certain substances, as well as stabilization of sludge are performed by means of a peat lining arranged in a thickness of 5 to 20 cm in at least some of the single caskets. With a further preferred mode of performance of the process according to the invention, in case of a sub-soil being sensitive to contamination, a compacted lining in a thickness of 30 to 40 cm used to be applied in at least some of the single caskets.

Brief Description of Drawings

A preferred embodiment of the sewage treating system according to the invention and an expedient mode of performance of the process to be applied in said system will be described in detail with reference to the drawing enclosed, wherein

Figure 1 is showing a schematical arrangement of a terrace-casketed sewage treating system according to the invention;

Figure 2 is the sectional view of the sewage treating system according to Figure 1 ;

Figure 3 illustrates the interconnection of two confining caskets - arranged in a terrace-like form - of the sewage treating system according to Figure 2;

Figure 4 is the side elevation of a preferred embodiment of an aerating wheel applied in the sewage treating system according to the invention, while

Figure 5 is the top view of the aerating wheel according to Figure 4.

Best Mode of Carrying out the Invention Figure 1 is by way of example only the schematical topview of a preferred embodiment of the sewage treating system according to the present invention. At one end of the sewage treating plant a discharging station 2 is to be found, essentially, sewage is introduced here. Next to the discharge station 2 a recipient 1 , receiving the "dead" sludge having been discharged from the caskets in the course of cleaning, is arranged. The dead sludge mixed with peat is used in agriculture. The sewage collected in the discharge station 2 arrives at the caskets 3 which are connected in series and are formed of the local soil. Connected in series with the caskets 3, caskets 4 of a larger area are to be found and at last, at the end of the sewage treating plant a filter 6 is coupled to the last casket 4. The whole sewage treating plant is surrounded by a drainage ditch 7, leading-off precipitation. Introduction of oxygen needed for purification is enhanced by means of aerating wheels 5 arranged in the water-stream in the single terraces. In the caskets 3and 4 traps (not illustrated here) are arranged, the task of which is to catch floating matter arrived with the water to be treated or formed in course of purification.

The arrows in the figure indicate the direction of movement of the water to be cleaned, i. e. having been already treated.

Figure 2 is a sectional view of the sewage treating system according to Figure 1. From the figure the terraced arrangement of the caskets 3, 4 becomes obvious, different water-depths in caskets 3 and 4 are also shown clearly. Caskets 3 and 4 are separated from each other by a barrage Sewage collected in the discharge station 2 is passing first through the caskets 3 of smaller area wherein a significant amount of the contaminants will be bound. From here sewage water arrives at the caskets 4 of a larger area and the essentially cleaned water is led to the filter 6 coupled to the last caskets 4, wherein liviog beings, in particular algae, are removed. Sewage to be cleaned is led then through coarse-granulated sand and cleaned water is discharged through a pipe 9 and it may readily be used for both industrial or agricultural purposes. It should be mentioned that in case of necessity, if a further decrease of the concentration of certain contaminants is required, an after-filtration may be performed on zeolite.

Figure 3 shows the interconnection of two confining caskets connected in series, as well as soil composition in the single caskets.

As soon as the water level has reached a certain height, water is streaming via a through-flow 10 to the next casket. Inflowing water puts the aerating wheel 5 into motion, by means of which the quantity of oxygen needed for purification is increased. The through-flow pipe 10 is led through the barrage 8 consisting of impermeable soil. In order to decrease the number of bacteria and/or for the sake of selection and adsorption of certain materials, as well as for stabilization of the sludge, at loast some of the casket may be lined with peat in a thickness of 5 to 20 cm. In the proximity of the inflow of the water arriving via the through-flow 10, on the peat lining 12 there is a synthetic foil 13 arranged. It should be noted that if the subsoil 11 of the caskets is sensitive to external contaminations, at least some of the caskets is to be lined with a compacted material in the thickness of 30 to 40 cm.

In Figures 4 and 5 an expedient embodiment of the aerating wheel 5 to be used in the sewage treating system according to the present invention is shown. The aerating wheel 5 is built-up of a carrier 14 adjustable in height, of two rotating parts 15 connected to a rod 16 which again. is fitted telescopically into the carrier 14. The aerating wheel 5 is driven by the energy of the streaming water.

In Figure 5 the design of the rotating parts 15 of the aerating wheel 5 is to be seen.

In a terraced-casketed sewage treating system formed in accordance with the invention comprising 5 to 25 caskets connected in series and formed of the local soil, the time interval needed for purification changes between 25 and 140 days. The system may also contain a casket with a water-depth of 2 to 6 m, said casket having the character of an anaerobic lake. This is followed by the caskets with a water-depth of 1,0 to 2,5 ra of lake-character and, by the caskets with a water-depth of 0,3 to 1,2 m having an aerobic lake character.

The aerobic caskets are arranged in a terrace-like manner, while the remaining caskets should be formed, if possible, at least partly terraced, so as to ensure easy changeability of water level.

With the exception of the first (anaerobic) phase, purification requires a considerable quantity of oxygen. This requirement is met by allowing air into the liquid phase from the atmosphere enhenced by the use of the aerating wheels arranged at the inflow into the caskets, by the photosynthesis of the vegetation and by dissolution on the water surface. Out of this, the most important factor is represented by the aerating wheel which is driven by the energy of water and ensures - independent of the external environmental factors - an approximate saturation of the water arriving at the caskets. This is most important in night-hours and, in particular, in wintertime.

For retaining floating parts of the sewage arriving at the plant, swimming vegetation resulting from purification, on the very place of inflow or arising, suitable traps are arranged prior to the outflow from the caskets.

After the caskets slow filtration is performed on coarse sand, thus removing floating living beings - in particular algae - from cleaned water. In case of increased requirements in respect to ecology are to be met e. g. concentration of certain materials, as e. g. ammonia is to be decreased, after-filtration on zeolite may also be inserted.

As already mentioned, to accelerate sludge-stabilization and to decrease the number of bacteria, the caskets may be provided with a peat lining and, if required by the quality of the subsoil, a lining of compacted material may also be used.

In the last 1 to 5 aerobic casket changeability of the water level may be utilized also during average operation (in general between 0,3 and 1,5 m ) . In such a manner, the quantity of the discharged and cleaned sewage can be timely separated from the quantity of the inflowing sewage. In relation to the recipient this means simultaneously an elastic regulation of water quality. Changing of water level means a storage of a water quantity of 10-60 days, accordingly, quantity of effluent water can be co-ordinated with the water yield of the recipient. It should be noted that capacity of the slow filters equals to the multiple of that of the plant.

Sewage, arriving through pipes or by vehicle at the terraced- casketed sewage treating plant, is charged into the first anaerobic casket. In the anaerobic caskets connected in series the sewage looses the major part of its floating matter content and becomes free of scum. A part of organic substances is decomposed in the course of the anaerobic processes, intensity of decomposition can be well observed by gas development.

In the caskets having been formed with a lake-character decomposition of organic substances is continued, partly in anaerobic , partly in aerobic way . In these caskets living beings and oxygen begin to appear.

In the aerobic caskets, in the sewage water becoming more and more richer in oxygen - dissolution of which is taking place as previously described - the majority of the remaining organic substance is decomposed, the water becomes nearly saturated with oxygen; minerals resulting from decomposition are incorporated partly into the vegetation, partly into the environmental biocoenoses. At last, most part of the biomass goes into the bottom sludge of the casket.

Mainly, in summertime, with the purpose to remove floating algae occuring in an increased quantity and to decrease concentration of other contaminations, water is filtered - with low filtration - through coarse sand. Thereafter, water is recycled into the recipient, or it is released for secondary use.

Peat in the caskets promotes growth of fungi. The byproduct of the diverse fungi is a bacterium-selecting antibioticum. By virtue of their ion-exchanging capacity, humic substances of peat can change the solubility of the different compounds, in such a manner solution of several organic substances can be reduced, compounds with heavy metal content are also bound.

As a by-product of the treatment, the sludge is collected at the bottom of the caskets and becomes stabilized for the most part by cold rot. After having disconnected the given casket and reduced its water-level (by siphoning), removal begins with scattering peat, broken straw or cornstalk. The mixed sludge - having a consistency being suitable for shoveling - will be removed with a bagger. Cleaning may be performed in a manner that the sludge is delivered by a snifting vehicle to the peat-bed next to the plant or, on the spot of use and mixed into the peat-bed. The material with a high content of organic matter is used for plant cultivation. Daggering of the first (anaerob) caskets is to be performed in every

1-2 year, the othor caskets are to be baggered in 3 to

10 year intervals. Technology enables continuous subsequent baggering of all the caskets of the plant.

It seems to be expedient to build the sand-filters for alternating operation. The upper layer should be changed in 3 to 10 weeks, the wholα filling is to be changed in 0,6 to 2,0 years. Removed coarse filter sand is placed on agricultural areas. Filter velocity lies in the range between 0,05 to 0,5 m³/h. The advantage of the sewage treating system according to the present invention lies in that its energy requirement practically equals to zero. It should be mentioned that the system can also be provided with swimming aerating means supplied from a separate energy source, in which case the capacity of the water purification plant can be increased even by 100 %.

Operation of the system docs not require permanent super- vision, the sludge formed in course of purification, the mixed sludge, is well suitable for further use. In compliance with prevailing demands, the system can be optionally enlarged, the capacity thereof can be increased. Investment and operational costs are low, environmental contamination is practically excluded. The sewage treating plant operates - together with the sand filter - free of failures even after turning to ice. However, it should be mentioned that in course of designing it is to be considered that periods rich in precipitation may result in a sudden rise of the water-level in the first casket, so emergency overflows are to be provided for.

By using such terraced-casketod sewage treating systems, canalization and sewage purification in small settlements can be quickly and cheaply solved. By moans of the system, purification of live waters can be realized in a short time. The system according to the present invention is well suitable for neutralizing dung water, vegetable nutritive matters contained in the dung and accumulated in sludge can be further utilized.

Claims

1. Terraced-casketed sewage treating system for simultaneous or separate purification of sewages of different origin, so e. g. snifted sewages, dung water, etc. based natural biological decomposition, built-up of a plurality terraced caskets of different size and with different water-depth, c ha r a c t e r i z e d in that it consists of caskets (3, 4) connected in series, the majority of which being lined - at least partially - with peat (12) and optionally lined on the bottom with a compacted material, furtheron the system is provided with aerating wheels (5) arranged in the water stream between the single caskets promoting the introduction of oxygen needed for purification, said system being further optionally equipped with scum-traps placed in the caskets (3, 4) and with slowly operating filters (6) for the removal of floating matters.

2. Terraced-casketed sevage treating system as claimed in claim 1, c h a r a c t e r i z e d in that it comprises at least five caskets (3, 4) in total which are arranged one after the other, some of them with a smaller area and with a water-depth of 1,0 to 2,5 m and compared to these, caskets with a larger area, with a water-depth of 0,3 to 1,2 m with an aerobic character, before which at least one casket, expediently with a water-depth of 2 to 6 m, with an anaerobic lake-like character may also be inserted.

3. Terraced-casketed sewage treating system as claimed in claim 1 or 2, c h a r a c t e r i z e d in that the caskets are arranged in a terrace-like manner so as to enhance introduction of air.

4. Terraced-casketed sewage treating system as claimed in any of the claims 1 to 3, c h a r a c t e r i z e d in that it comprises at least one aerating wheel (5) driven by the flow energy of the sewage water to be cleaned.

5. Terraced-casketed sewage treating system as claimed in any of claims 1 to 4, c h a r a c t e r i z e d in that in the caskets (3, 4) each, in a depth of 10 to

30 cm at most, there is a trap for catching the floating substance arriving with the sewage or produced in the course of purification.

6. A process for performing purification in sewage treating system according to claim 1, c h a r a c t e r i ze d in that for the removal of living beings contained in water, in particular algae, as a slow filter (6) coarse granulated sand is used and, in dependence of demand, an after-filtration is performed on zeolite to reduce the concentration of certain contaminants.

7. A process as claimed in claim 6, c h a r a ct e r i z e d in that a decrease of number of bacteria, the selection, adsorption of certain materials, as well as the stabilization of sludge are achieved by means of a peat lining which is arranged in the caskets in a thickness of 5 to 20 cm.

8. A process as claimed in claim 6 or 7, c h a r a c t e r i z e d in that with a subsoil (11) being sensitive to external contaminations in the caskets each (3, 4) a lining of a compacted material in a thickness of 30 to 40 cm is applied.