EP0923505A1

EP0923505A1 - Method and equipment for off-shore treatment of communal sewage water

Info

Publication number: EP0923505A1
Application number: EP98905208A
Authority: EP
Inventors: Zdenek Davidek; Jiri Karlach; Jir I C Ejka
Original assignee: Skoda JS AS
Current assignee: Skoda JS AS
Priority date: 1997-07-03
Filing date: 1998-03-05
Publication date: 1999-06-23
Also published as: SK31199A3; CZ211497A3; WO1999001388A1; CZ285328B6; HRP980033A2

Abstract

Sewage from a residential agglomeration is accumulated on the coast and subsequently pumped through piping to at least one anchored floating body of a technological equipment carrier, where it is treated, and the treated sewage is partly used as operational water in the treatment process and partly discharged, whereas substances retained and separated in the technological process of treatment are stored and/or packed and subsequently removed for final liquidation or utilization. The equipment to make use of this method of treatment comprises technological equipment with tanks with an open water surface, to which sewage is supplied through piping. It is composed of at least one floating body of the technological equipment carrier (1), which is anchored and comprises at least one pontoon with a double, circular or at least quadrangular shaped, bottom (24), and a double casing (23), in which are arranged watertight chambers. The ratio of the width B of the body of the technological equipment carrier (1) to its draught T is in the range of 8.5 to 12.5 and the metacentric radius r0 of the body of the technological equipment carrier (1) is in the range of 15 to 26. The watertight chambers of the partitioned double bottom (24) form ballast tanks to stabilize the changing weight ratios that occur in the treatment of the sewage.

Description

METHOD AND EQUIPEMENT FOR OFF-SHORE TREATMENT OF COMMUNAL SEA AGE WATER

Field of the invention

The invention concerns a method of treating communal sewage water from medium-sized and larger sources of pollution, especially in maritime areas, and equipment to carry out this method.

Descriprion of the prior art

In maritime areas with a broken hilly and mountainous coast, for example in areas of the Mediterranean Sea and many other locations, the configuration of the coast does not permit the acquisition of suitable space for the construction of a sewage treatment plant. Most towns and urban units situated in such a terrain at steep coastal mountain locations therefore discharge sewage water straight into the sea, which is polluted. The degree of sea pollution increases considerably in the tourist season, when the number of inhabitants at these locations rises sharply in comparison with the number of permanent inhabitants. In this manner the demand arises for the adaptability of water treatment output in these two different seasons. Obstacles so far in the way of the construction of municipal sewage treatment plants at the localities mentioned can be expressed as follows. On the one hand it is practically impossible to acquire a suitable and adequately large site for the surface construction on land of a sewage treatment plant in the given relief of the coast. From the point of view of the need for a natural declivity the plant should be situated on the coast, where the life of a harbour town is usually concentrated and where beaches with tourist and hotel facilities used for recreation are located. Another obstacle is the necessity to ensure the varying output of water treatment with regard to the above-mentioned substantial increase in the number of inhabitants during the tourist season. Summary of the Invention

The disadvantages of the current technological situation are eliminated to a great extent by the method of communal sewage water purification and the array of equipment to carry out this method which contains technological equipment with tanks with an open water area to which sewage water is supplied through piping. Sewage water from a housing agglomeration on the coast is accumulated and subsequently is pumped through pipes to at least one anchored floating body of a carrier of the technological equipment of the plant, where it is treated, and the purified sewage water is both partially used as service water in the treatment process and discharged, whereas substances caught and separated from the technological process of treatment are stored and/or packed and subsequently removed for final liquidation or utilization. An advantage is that the method of communal sewage water treatment according to this invention can be used in places where the configuration of the sea coast does nor permit suitable space for the construction of a sewage treatment plant. This equipment is composed of the floating body of the carrier of the technological equipment which is anchored and is made up of at least one pontoon with a double bottom, where the bottom is in the shape of a circle or at least a quadrangle, and a double casing, in which watertight chambers are arranged and where the relation of the width B of the body of the carrier to its draught T is in a range from 8.5 to 12.5 and the metacentric radius r₀ of the body of the carrier is in a range from 15 to 16. The watertight chambers of the divided bottom make up ballast tanks to balance the changing weight relations in the treatment of the sewage water.

The double bottom and casing of the floating body of the carrier of the technological equipment ensures ecological safety in the event of any breakdown in the impermeability of the plant, the watertight chambers serve in such a case as safety cisterns. The watertight chambers of the divided double bottom are also partially used to advantage as ballast tanks to balance the changing weight relations in the treatment plant process.

The shape of the body of the carrier and the relations given for its width and draught and also its metacentric radius have an effect on achieving the highest possible stability of the floating body of the carrier against inclinations in all directions. Thanks to this shape the maximum amount of surface moment of inertia of the main water line is achieved, which influences how high the metacentric height is. The stability of the floating body of the carrier is a necessary condition in ensuring the technological function of the installed purification equipment, which works on the basis of the gravitational flow of the treated water between individual treatment stages.

The relation of the width B of the body of the carrier to its draught T is to advantage in a range from 10.3 to 11.3 and the metacentric radius r₀ of the body of the carrier is to advantage in a range from 21 to 22.5. In these ranges the highest amount of stability of the floating body of the carrier is achieved. The equipment for purifying communal sewage water according to this invention is designed to be located on a wavy surface with a wave height up to one metre, under these conditions the inclination of the floating body of the carrier is approximately 1°.

The technological tank of the plant with the greatest open water area is to advantage situated at the centre of the body of the carrier and another two technological tanks of the plant with the second and third greatest open water area are arranged opposite each other and are mutually connected around its circumference. The technological tank of the plant with the greatest open water area is best in a circular shape. With this arrangement of tanks their buffer action is made use of to reduce the extent of inclination of the body of the carrier.

All three technological tanks have to advantage a joint plane of syrnmetry which is orientated in the direction of the dominant winds. This contributes to increasing the stability of the body of the carrier.

Equipment according to this invention can contain mutually connected bodies of carriers, for example with the aid of pins and bolted joints. A greater number of floating bodies of carriers means the capacity of the plant can be adapted to the varying demands both in the course of a season and at the place of location.

An advantage of this invention is the fact that it is possible to utilize relatively cheap treatment technology which is arranged on the floating body with a high stability against tipping. This ensures a sufficiently stable surface in the tanks of the treatment equipment with an open water area.

Brief description of the drawings

For better clarification of the invention examples of the invention workmanship are depicted in the appended Figures 1-5, which are subsequently described in more detail. The floating equipment for communal sewage water treatment is depicted in graphic form in Fig.l in its axonometric projection, containing the technological equipment with tanks with an open water area to which sewage water is supplied through pipes. The octagonal floating body of the carrier of the technological equipment of the plant is given as a top view in Fig. 2 with a schematic diagram of individual pieces of equipment located on it, vertical cross sections of the equipment are given in Figs. 1 and 5 according to Fig. 2 in two planes perpendicular on themselves going through the centre of the equipment. In Fig. 4 the equipment according Fig. 2 can be seen in a horizontal cross section with the layout of the technological equipment.

Description of the Preferred Embodiments

The equipment for communal sewage water treatment, containing the technological equipment with tanks with an open water area according to this invention, is arranged on the floating carrier .1, made up of a steel modular construction. The pontoon has a double bottom 24 in the form of a polygon (this can be a square, rectangle, octagon, etc.) or a circle, and the double casing 23, in which the watertight chambers are arranged. The size of the diagonal or diameter of the bottom can be 32 metres, the height of the casing 7 metres. The watertight chambers ensure ecological safety in the event of any breakdown in the impermeability of the plant and serve as safety cisterns. The chambers of the divided double bottom 24 can also be partially utilized as ballast tanks to balance the changing weight relations in the process of the plant's work. Built into the mentioned steel construction of the floating body of the carrier 1. is the technological equipment of the plant, including tanks made of rustless steel for the captation of sewage water in the course of the treatment process. This sewage water is supplied to the equipment through pipes (not in the diagram).

The shape of the bottom 24 of the body of the carrier !_ of the technological equipment (a circle, or polygon - at least a quadrangle) is important in achieving the greatest possible stability of this body against inclination in all directions by the same amount of the stability moment (the moment given by the size of the arm of stability occurring because of a shift in the gravitational centre of the displacement in the event of the floating body being deflected from its equilibrium). It is thanks to the shape of its bottom that the maximum surface moment of inertia of the main water line (the surface intersecting the floating body) is achieved, which has a direct influence on the size of the metacentric radius r₀ = I_x/D, where I_x is the surface moment of inertia of the main water line and D is the displacement. In experiments it has been verified that in the case of the equipment according to this invention a size of r₀ = 24 was achieved, whereas it is known that the usual r₀ values for naval ships are in a range from 0.8 to 1.5.

With a diameter of d = 32 metres and draught of T = 2.5 metres of the floating body of the carrier 1_ of the technological equipment the ratio of the side height H to the draught T of this body of the carrier 1_ is at least 2.2 and the ratio of the diameter or diagonal d of its bottom to the draught t is at least 12.8. The ratio of the width B of the body of the carrier 1_ to its draught T is to advantage in the range from 10.3 to 11.3. These values characterize the very good stability of the floating body of the carrier 1, which is a necessary prerequisite in ensuring the technological function of the installed treatment equipment, which works on the basis of the gravitational flow of the treated water between individual treatment stages (tanks). It is evident that even the period of swing of the floating body of the carrier 1 must meet the condition of not being located in the resonant area of the frequency of the acting water. For the reasons given above the floating body of the carrier 1. according to this invention is designed for location on a wavy surface with a wave height up to one metre.

The equipment for communal sewage water treatment, containing technological equipment with tanks with an open water area, is designed for medium-sized and larger urban sources of pollution lying on the sea coast. In general the method of solution takes place in module form in two basic sizes which differ in the technological stabilization of the plant's sludge. One of them (designed for an agglomeration with from 5,000 to 20,000 connected inhabitants) works with the full aerobe, joint stabilization of sludge, the second (designed for agglomerations with from 25,000 to 100,000 inhabitants) works with the full anaerobe stabilization of sludge. Individual modules can be connected in from twos to fours depending on the size of the pollution source. The location of the equipment is suitable in a protected inlet or behind a protective breakwater in a place providing a depth of water of 4 metres with the wave height not exceeding approximately one metre away from a residential or recreational zone on the surface of the sea. The whole facility is fixed by anchoring chains tied to anchoring blocks on the seabed.

Sewage water from housing agglomerations is removed via sectioned drainage into underground accumulation tanks of the pumping station, located on the coast at the shortest possible distance from the anchorage site of the floating equipment according to the invention. From this pumping station sewage water is pumped to the equipment through floating piping or piping placed on the seabed. At the pumping station pumps are used requiring no mechanical protection, with high profile continuity of hard particles.

Sewage water is transferred to the stage 2 of rough pre-treatment (a combination of mechanical and hydraulic treatment), where rakings (rough impurities), sand and fats are removed. These components are placed partially in containers 4 (caught and extracted substances) and partially packed into foil (rakings). From the stage 2 of rough pre-treatment sewage water is conducted down a gradient to the biological stage of treatment, containing a contactor 6, denitrification tank 7, nitrification tank 9 and induction tank 10 with scraping of the bottom and surface and with the submerged collection of offset water. The aerobe treatment process (with the use of blowers 8) takes place in these tanks in the usual manner. Sludge farming is connected with the biological stage of treatment, made up of a multipurpose two-chamber tank 11. for primary handling of the sludge (if necessary two tanks) for drawing off sludge water and the opportunity to mix the medium pneumatically. Also involved is the homogenization tank 14 with mechanical sludge storage. Chemical farming 17 with dissolvent and dosing tanks with the relevant mixing and pumping technology, including the operative storage of chemicals for sludge stabilization, is also installed for the proper functioning of this equipment. From the homogenization tank l i the sludge is pumped through to the belt press, where in two stages pre-compression takes place and then sludge removal. The removed sludge is transported through worm pumps to the main deck of the floating body of the carrier 1_ into storage containers 4. Two diesel aggregates 2 _ (200 kVA) are located in the body of the carrier 1_ for the functioning of the plant which alternately switch in order that uninterrupted operation of the plant is ensured. There is also an emergency diesel aggregate 22 (40 kVA) in the engine room which secures breakdown operation in the event of an operative diesel aggregate 21 cutting out.

The whole floating facility secures living conditions for the service staff supervising the fully automated running of the sewage water treatment plant. Once a week compressed sludge, rakings, extracted sand and fats are removed with the service vessel for the further utilization of raw materials extracted from the treatment process. Removed, stabilized sludge can be used to advantage in the event of its appropriate quality to fertilize agricultural land directly, to produce compost or for recultivations. Final liquidation of rakings and fats is expected at a dumping site or in a communal waste incinerator. Final liquidation of sand is also expected at a dumping site or again in the production of compost.

The spacing of individual tanks of the technological equipment of the plant with regard to the total configuration of the floating body of the carrier 1 of the technological equipment is selected in such a manner that the lowest possible influence is achieved of free, open surfaces of the water area on the stability of the whole floating body. The technological tank of the plant with the greatest open water area (the induction tank H)) is located in the middle of the body of the carrier 1_^ and another two technological tanks of the treatment plant with the second and third greatest open water area (the denitrification tank 7, the nitrification tank 9) are arranged opposite each other around its circumference. The connection of these tanks has the effect of a buffer element lowering the amount of inclination of the floating body of the carrier 1.

All three of the above-mentioned technological tanks (the denitrification tank 7, nitrification tank 9, and induction tank 10) have a joint plane of symmetry which is orientated in the direction of dominant winds. In this manner stability of the floating body of the plant against inclination is further enhanced.

The communal sewage water treatment plant according to this invention in its given configuration is a design fully secured with its own energy resources, alternatively the necessary electrical energy can be supplied from the shore. A management and control work point, microlaboratory equipped in the relevant manner (e.g., for semi-automatic setting of the biochemical consumption of oxygen 5, chemical consumption of oxygen, turbidity metering, etc.), workshop space and a storeroom for replacement parts, and social facilities for the service staff can also be located on it.

With regard to the quality of the processed sewage water, an increased concentration especially of suspended and extractable matter from the operations of recreational establishments, hotels and restaurants can be expected.

Because the equipment according to the invention can contain mutually connectable bodies of carriers, the output of the treatment equipment can be adapted to the size of the pollution source in the course of a season (important in tourist areas) and with the development of construction in a given locality.

The sectional nature of the ship construction and the total module lay-out (see, for example, the interfaces 3 of modules) make the transfer of equipment according to this invention possible in the form of pressure assembly to the place it is located.

Industrial Use of the Invention

The equipment according to the invention is designed for the treatment of communal sewage water from medium-sized and larger residential sources of pollution situated on the sea coast.

Claims

1. The method of communal sewage treatment from residential sources of pollution, in particular those situated at the sea coast, characterised by the fact that the sewage from a residential agglomeration is accumulated on the coast and subsequently pumped through piping to at least one anchored floating body of a technological equipment carrier, where it is treated, and the treated sewage is partly used as operational water in the treatment process and partly discharged, whereas substances retained and separated in the technological process of treatment are stored and/or packed and subsequently removed for final liquidation or utilization.

2. The equipment to make use of the method of communal sewage treatment according to claim 1, comprising technological equipment with tanks with an open water surface, to which sewage is supplied through piping, characterised by the fact that it is composed of at least one floating body of the technological equipment carrier (1), which is anchored and comprises at least one pontoon with a double circular or at least quadrangular shaped bottom (24), and with a double casing (23), in which are arranged watertight chambers , and where the ratio of the width B of the body of the carrier (1) to its draught T is in the range of 8.5 to 12.5 and the metacentric radius r₀ of the body of the carrier (1) is in the range of 15 to 26, whereby the watertight chambers of the partitioned double bottom (24) form ballast tanks to stabilize the changing weight ratios that occur in the treatment of the sewage.

3. The equipment according to claim 2, characterised by the fact that the ratio of the width B of the body of the technological equipment carrier (1) to its draught T is in the range of 10.3 to 11.3.

4. The equipment according to claims 2 or 3, characterised by the fact that the metacentric radius r₀ of the body of the technological equipment carrier (1) is in the range of 21 to 22.5.

5. The equipment according to any of the claims 2 to 4, characterised by the fact that the technological tank of the treatment equipment having the largest open water surface is located in the centre of the body of the technological equipment carrier (1) with another two technological tanks of the treatment equipment around its circumference with the second and third largest open water surface being arranged opposite each other and mutually connected.

6. The equipment according to claim 5, characterised by the fact that the technological tank of the treatment equipment with the largest open water surface is of a circular shape.

7. The equipment according to claim 5 or 6, characterised by the fact that all three of the technological tanks have a joint plane of symmetry which is orientated in the direction of the prevailing winds.

8. The equipment according to any of the claims 2 to 7, characterised by the fact that it comprises at least two bodies of carriers, mutually connected.

AMENDED CLAIMS

[received by the International Bureau on 28 August 1998 (28.08.98); original claim 1 cancelled ; remaining claims unchanged (2 pages)]

1. Equipment for communal sewage treatment, comprising technological equipment with tanks with an open water surface, to which sewage is supplied through piping, characterised by the fact that it is composed of at least one floating body of the technological equipment carrier (1), which is anchored and comprises at least one pontoon with a double circular or at least quadrangular shaped bottom (24), and with a double casing (23), in which are arranged watertight chambers , and where the ratio of the width B of the body of the carrier (1) to its draught T is in the range of 8.5 to 12.5 and the metacentric radius r₀ of the body of the carrier (1) is in the range of 15 to 26, whereby the watertight chambers of the partitioned double bottom (24) form ballast tanks to stabilize the changing weight ratios that occur in the treatment of the sewage.

2. The equipment according to claim 1, characterised by the fact that the ratio of the width B of the body of the technological equipment carrier (1) to its draught T is in the range of 10.3 to 11.3.

3. The equipment according to claims 1 or 2, characterised by the fact that the metacentric radius r₀ of the body of the technological equipment carrier (1) is in the range of 21 to 22.5.

4. The equipment according to any of the claims 1 to 3, characterised by the fact that the technological tank of the treatment equipment having the largest open water surface is located in the centre of the body of the technological equipment carrier (1) with another two technological tanks of the treatment equipment around its circumference with the second and third largest open water surface being arranged opposite each other and mutually connected. 11

5. The equipment according to claim 4, characterised by the fact that the technological tank of the treatment equipment with the largest open water surface is of a circular shape.

6. The equipment according to claim 4 or 5, characterised by the fact that all three of the technological tanks have a joint plane of symmetry which is orientated in the direction of the prevailing winds.

7. The equipment according to any of the claims 1 to 6, characterised by the fact that it comprises at least two bodies of carriers, mutually connected.