DE3808297A1 - Rainwater treatment and duct flushing by novel street inlets (syphon gulley) - Google Patents

Abstract

The rainwater treatment and duct flushing by syphon gulleys is an effective concept for the renovation and new construction of drainage systems. The simple principle of the syphon permits a robust and operationally reliable design of the street inlets with a high degree of retention for dirt and impurities in order to protect the bodies of water. The tests with a prototype have proved the technical feasibility and reliability, even in the presence of a large amount of dirt and impurities.

Description

Technical concepts of urban drainage

Cities are drained either in the mixed system or in the separation system. Street inlets are used in both systems, which are referred to below as gullies. In the mixing system ( Fig. 2, top), dirty water and rainwater flow in a sewer pipe to the sewage treatment plant. In the separation system ( Fig. 2, bottom), on the other hand, only the dirty water flows to the sewage treatment plant, but the rainwater in a second sewer pipe without cleaning directly into a body of water. The entire wastewater from mixing systems cannot be treated in the wastewater treatment plant in heavy rain. In mixed systems there are therefore discharge points (rain overflows) which start between 5 and 50 times a year and thereby discharge unpurified wastewater into the water. Most city centers are drained by mixed systems, the peripheral areas by separation systems.

Conventional street inlets

Road drainage technology in the Federal Republic of Germany almost exclusively uses dry or wet gullies according to DIN 4052 (1977). The common forms of gullys are described below: The water flowing off the street is mechanically cleaned in a dry gully ( Fig. 3, left) using a sludge bucket. The water escapes through the slots in the bucket. When the bucket is filled with solids, the water flows through the top row of holes, which serves as an emergency overflow. At the end of the rain, all water flows through the slits or holes in the bottom of the bucket to the canal, so that the gully falls dry. In the wet gully ( Fig. 3, right), the water is also cleaned mechanically, but here by depositing the dirt particles in the gully sump. There is no drainage delay with either type, which means that the time distribution of the gully inflows is equal to the gully outflows. The variants of the dry or wet gullies differ only in the different bucket sizes or sump volumes and an odor trap required for use in the mixing system, but not in the type of cleaning and the drainage of the draining water. A detailed description of the structural designs can be found, for example, in the catalogs of the manufacturers Passavant (K85 duct casting catalog) or Buderus (duct casting 82). Proof of hydraulic performance was provided by Thiele (1983).

Problems with water protection and canal operation

In connection with the above Gullys focuses on two problems the functioning of sewer networks. For one thing, it is from Rainwater draining off road surfaces is often much stronger dirty, such as the processes of sewage treatment plants. With every rain, pollutants become from the rainwater channel carried into the water. Extensive measurements and Calculations about the pollutants contained in the rainwater were carried out by Grottker (1987). On the other hand, tend special flat positions in sewer networks for deposits of Pollutants. These pollutants mostly have to be regular be removed by high pressure flushing. About 1% of all Postures need to be rinsed more than once a month, most once or twice a year. In one shift with  two men and a modern high-pressure flushing car can hold about 5 up to 10 poses can be rinsed. Would not find these douches instead, in extreme cases the pipe cross-section may be relocated come with extremely unpleasant side effects for the connectee. It would come in mixed systems in rainy weather, moreover to even larger contaminant inputs into the water, since the discharged waste water is still there would be more enriched with whirled channel sediments.

Task

The object of the invention is to create a gully in the sense of water protection less pollutants get into the water, with additional the sewer network operating costs are reduced. It is now proposed in the drainage of rainwater canals and in Attitudes of mixed water channels at risk of sedimentation instead of the usual dry or wet gullies, new street inlets to install. The invention based on the Exemplary embodiments shown in the drawings explained.

Fig. 1 shows the top view of an end strand of a city drainage system in the separation process ( 2 ). The dirty water pipes of the households ( 4 ) are connected to the dirty water channel ( 6 ), the rain water pipes ( 8 ) of the roof surfaces to the rain water channel ( 10 ). The street gullies ( 12 ) are also connected to the rainwater channel ( 10 ). The channel section between two shafts ( 14 ) is referred to as channel maintenance ( 16 ). Several gullies ( 12 ) can be connected to a sewer system ( 16 ).

Fig. 2 shows the cross section of a residential street, the drainage is designed as a mixing system ( 20 ) - above - and as a separation system ( 22 ) - below. In the mixing system, all household sewage pipes ( 24 ) (rainwater and dirty water) are led into the mixed water channel ( 26 ). The gullies ( 12 ) are also connected to the mixed water channel ( 26 ). In the separation system, the dirty water pipes ( 4 ) are connected to the dirty water channel ( 6 ) and the rain water pipes ( 8 ) and the gullies ( 12 ) to the rain water channel ( 10 ).

Fig. 3 shows a conventional dry gully ( 30 ) and wet gully ( 32 ) consisting of a grate made of cast iron ( 34 ), which is stored in a frame made of cast iron with a bucket support ( 36 ). The sludge bucket ( 38 ) is suspended in the frame ( 36 ) of the dry gully ( 30 ). The support ring ( 40 ) establishes the connection between the frame ( 36 ) and the shaft ( 42 ). In the dry gully, this shaft ( 42 ) rests directly on the floor with a basic outlet ( 44 ). In the wet gully ( 32 ), the shaft ( 42 ) rests on a sleeve part ( 46 ), an intermediate part ( 48 ) and a closed bottom ( 50 ).

Fig. 4 shows the novel wet gully with siphon (Hebergully), sludge bucket and throttle with attack, in the separation system ( 54 ). Consisting of a closed bottom ( 50 ), an intermediate part ( 48 ) and a socket part ( 46 ). A throttle ( 58 ) with a throttle opening ( 60 ), an overflow ( 62 ) and a cover ( 64 ) is inserted into the outlet ( 56 ) of the sleeve part ( 46 ). The outlet leads to the rainwater channel ( 10 ). The stowage area is referred to as the gully sump ( 66 ). Above the sleeve part ( 46 ) there is in turn an intermediate part ( 48 ) with a circular hole ( 68 ) through which the lifting tube ( 70 ) is inserted. The lifting tube ( 70 ) ends within the gully about 5-10 cm above the closed bottom ( 50 ). Outside the gully, the siphon pipe ( 70 ) is designed as an odor trap ( 72 ). The lifting tube ( 70 ) opens into the dirty water channel ( 6 ). Above the intermediate part ( 48 ) there is a shaft ( 42 ), a support ring ( 40 ), a frame made of cast iron with a bucket support ( 36 ) in which a sludge bucket ( 38 ) hangs and a grate made of cast iron ( 34 ) analogous to the construction of the Dry gullies ( 30 ).

Fig. 5 shows the new type of wet gully in the simplified version (overflow gully) without lifter and without sludge bucket, in the mixing or separating system ( 76 ). Consisting of a closed bottom ( 50 ), an intermediate part ( 48 ), a sleeve part ( 46 ) and a throttle ( 58 ) with throttle opening ( 60 ), overflow ( 62 ) and cover ( 64 ). The stowage area is referred to as the gully sump ( 66 ). Above the sleeve part there is a shaft ( 42 ), a support ring ( 40 ), a frame made of cast iron with a bucket support ( 36 ) and a grate made of cast iron ( 34 ).

Fig. 6 shows a new type of wet gully with lifter and sludge bucket but without throttle with hold-up, in the mixing system ( 78 ). Consisting of a closed bottom ( 50 ), three intermediate parts ( 48 ), a shaft ( 42 ), a support ring ( 40 ), a frame made of cast iron with a bucket support ( 36 ) in which the sludge bucket ( 38 ) hangs and a grate made of cast iron ( 34 ). In the uppermost intermediate part ( 48 ) there is a circular hole ( 68 ) through which the lifting tube ( 70 ) is inserted. The lifting tube ( 70 ) ends within the gully about 5-10 cm above the closed bottom ( 50 ). Outside the gully, the siphon pipe ( 70 ) is designed as an odor trap ( 72 ). The lifting tube ( 70 ) opens into the mixed water channel ( 26 ). The stowage area is referred to as the gully sump ( 66 ).

Fig. 7 shows the novel dry gully with modified sludge bucket, in the mixing or separation system ( 80 ). Except for the sludge bucket ( 38 ), the novel dry gully ( 80 ) is identical to the conventional dry gully ( 30 ) shown in FIG. 3. Consisting of a base with base outlet ( 44 ), a shaft ( 42 ), a support ring ( 40 ), a frame made of cast iron with a bucket support ( 36 ) and a grate made of cast iron ( 34 ). The modified sludge bucket ( 82 ) has a bottom with holes ( 84 ) so that the water can drain from the bucket. Apart from the overflow openings at the upper edge ( 85 ), it is otherwise closed.

In a further modification, instead of the sludge bucket ( 38 ), 3 sieves (coarse sieve ( 86 ), middle sieve ( 88 ), fine sieve ( 90 )) can be used suspended from one another.

Fig. 8 shows a dimensioning diagram for the new type of wet gully in the mixing or separation system ( 92 ). On the right abscissa is the catchment area of the gully A _{E, GU} [m²] ( 93 ), on the left abscissa the number of elevations n _Heb [1 / a] ( 94 ) and on the ordinate the rain donation r [l / s · ha] ( 95 ). In the left quadrant, the rain shower line of a thoroughfare with a continuous step of T = 1 min ( 96 ) is shown. The throttle characteristics ( 97 ) for throttle openings ( 60 ) from 0 to 7 cm in diameter with a diameter of the lifting tube ( 70 ) of 7.5 cm are entered in the right quadrant. The solid line ( 98 ) shows a design example for the mixing system ( A _{E, GU} = 200 m², throttle = 0 cm, r = 251 / s · ha, n _Heb = 801 / a), the dashed line ( 99 ) shows one Design example for the separation system, ( A _{E, GU} = 200 m², throttle = 3.5 cm, r = 1001 / s · ha, n _Heb = 201 / a).

How the new type of wet gully works with a siphon (Hebergully)

In the mixing system ( 20 ), the outlet of the gully is designed as a lifter and connected to the mixed water channel ( 26 ) ( Fig. 6). The water flowing off the street flows through the sludge bucket ( 38 ), in which the coarse water contents are retained. The water then falls into the gully sump ( 66 ), in which the fine particles can settle. In the event of small drainage events, the lifter ( 70 ) acts like a normal outlet with a low-lying intake. However, if a minimum inflow required for lifting is exceeded, the lifting begins, in which the gully sump ( 66 ) is emptied suddenly and the contaminants deposited in the gully sump ( 66 ) are entrained. With a jack diameter of 7.5 cm and an inflow of only 0.5 l / s, this mode of operation causes the start of lifting and thus an intermittent loading of the mixed water channel ( 26 ). The flushing rinses created in this way remobilize deposits in the position below, thereby reducing the dirt supply in the sewer and transporting it to the sewage treatment plant. The reduction of these pollutants contributes to water protection, since according to surveys by Brombach (1984) approx. 50% of the dirt loads chopped off at rain overflows come from sewage deposits.

The operation of the lifter ( 70 ) in the separation system ( 22 ) is comparable to that in the mixing system ( 20 ) ( Fig. 4). The decisive difference is that the lift gully in the separation system ( 22 ) is also used to separate contaminants. The discharge throttle is so large that the siphon ( 70 ) does not start at small to medium inflows, but the waste water, like in the conventional street inlet, is led into the water via the rainwater channel ( 10 ). Due to the throttled drain and the relatively low turbulence in the gully, the discharged dirt load is significantly reduced. Most contaminants settle in the gully sump. In the event of heavy rain, the gully empties via the lifter ( 70 ) with the contaminants accumulated in the gully sump ( 66 ) into the dirty water channel ( 6 ) and thus to the sewage treatment plant. The effect for water protection lies in this dirt separation. The additionally installed hold-up ( 78 ) ensures operational safety in the event of a possible blockage of the jack ( 70 ).

How the new type of wet gully works without a jack (hold-up gully)

In a simplified variant, the overflow gully ( FIG. 5), the drain from the gully is designed as a throttle ( 74 ). At low inflows, the outflow is throttled, thereby reducing turbulence. In heavy rain, the gully water level rises, whereby all water escapes through the raid. As a result, increased dirt retention is achieved compared to the conventional gully. There is no uplift.

How the innovative dry gully works

In the novel dry gully ( Fig. 7) only the sludge bucket ( 96 ) is modified. The construction without slots causes increased dirt retention due to the restricted flow through the holes in the bottom ( 84 ) of the gully. If the bucket is full during heavy rain, the waste water can flow through the overflow openings at the upper edge ( 98 ) so that the hydraulic output of the gully is not restricted.

Try a prototype

The gully was on one Test rig on a scale of 1: 1 for its hydraulic effectiveness regarding the generation of a flushing surge and one Separation of contaminants checked. A test report is currently under way created. The following design details are for how it works of greater importance:

• - hydraulically favorable shaped crown,
• - lifter diameter approx. 7-10 cm,
• - Slightly upward flow throttle flow to lock prevent by relatively heavy objects,
• - throttle opening in the falling area of the incoming rainwater, for automatic flushing of floating substances (paper, sheets, . . .) to guarantee,
• - throttle diameter approx. 2-7 cm,
• - odor trap with slight curvatures,
• - Tangential entry into the further channel,
• - Eccentric intake manifold eccentric and approx. 10 cm above the Sole of the gully sump,
• - Intake port of the jack on the passage through the gully shaft removable.

Dimensioning of the gully

The hydraulic dimensioning of the lift gully depends on its use in the mixing or separation system. In the mixing system, the dimensioning is very simple, since only a change in the drainage curve takes place here, but not a discharge distribution. The only variable dimension is the jack diameter. It influences the minimum inflow required for lifting. With a large diameter (10 cm), this minimum inflow of 2.1 l / s is much higher than with a smaller jack diameter (7.5 cm) with 0.5 l / s. In FIG. 8 is for a lifter diameter of 7.5 cm a design diagram set forth, which is suitable for the separation system as well as the mixing system. It was obtained from the test results with the prototype. The throttle characteristic for a throttle with a diameter of 0 cm can be used to demonstrate the light-off frequency in the mixing system, since there is no throttle in the mixing system and the water only escapes via the siphon. For a typical gully catchment area (street area) of 200 m², there are approx. 80 elevations per year. It is evident that with such a frequency of surge flushing, no larger deposits can form in the position below. A version of the lifting gully according to FIG. 4 is used in the separation system. Here, the discharge is divided by the throttle into the rainwater channel and via the lifter into the dirty water channel. A three-fold goal is pursued. On the one hand, the drain to the rainwater channel should be throttled as much as possible in order to keep flushing out of contaminants to a minimum. On the other hand, the number of lifts must be limited in order not to generate excessive proportions of extraneous water in the sewer. Thirdly, it is necessary to ensure that the gully sump is adequately flushed throughout the year in the dirty water channel. The optimal combination can be found with the help of the data on the local conditions and the dimensioning diagram. With a gully intake area of 200 m² and a selected number of 20 flushes per year, the throttle diameter is approx. 3.5 cm. In the event of the lifter failing due to blockages as a result of excessive lifter intervals, the hold-up serves to properly drain the drain.

Rinse

The one available for a flush The net content of the gully depends on the desired gully depth (65 up to 95 cm) between 100 l and 150 l. With a jack diameter of 7.5 cm and a (test) suction height of approx. 90 cm the drain in 100 s. The mean emptying rate is thus 1 l / s. In practical cases, the suction head should be lower because of the lower Sewer rather larger and thus the drainage time get even smaller. Pisano et al. (1979) give one empirically found relationship for that for a gush flush required amount of water:

V _rinse = (13.5 L ^1.45 D ^0.23 ) S ^1.40

with V rinse _{amount of} rinsing water in cf, L pipe _length in 100 ft, D pipe diameter in ft, S gradient in ft / 1000 ft. This can be used to calculate the effective rinsing length for a typical sedimentation-prone position: with 0.5% gradient, 25 cm pipe diameter and 100 l effective gully volume results in 83 m, a length which is in the order of the usual keeping lengths.

Separation of contaminants

The separation of contaminants happens at Hebergully in the mixing system as with conventional dry gully, because the dirt deposited in the gully sump when lifted is disposed of via the mixed water channel. In the separation system the dirt load washed off the street is divided into three parts Cut. The coarse contaminants are like in the sludge bucket held back at the dry gully. A lot of the little ones Dirt particles settle in the gully sump and are removed by the Lifter flushed into the dirty water channel. The little remaining Dirt escapes through the throttle and the rainwater channel Waters.

Refurbishment concept

The use of lifting gullies must be seen as part of a rehabilitation concept for conventional street gullies. This refurbishment concept includes yet another modification of the wet gully, the overflow gully ( FIG. 5), which is constructed similarly to the lifting gully in the separation system, but without a lifting device and sludge bucket. Furthermore, the dirt discharge can be reduced with the dry gully with modified sludge bucket ( Fig. 7) due to the restricted flow. There are three modifications to the street gullies for decentralized rainwater treatment:

• - the Hebergully described in detail above,
• - the raid drain as well
• - the modified sludge bucket.

The renovation concept sees two options for moving Retrofitting before:

1. Retrofitting without earthworks.
This solution is mainly used in existing drainage systems. In the separation system for the dry gully, there is an exchange of the sludge buckets and for the wet gully the conversion to a hold-up gully to increase the dirt retention. In the mixing system, the sludge bucket is also replaced in the dry gully and the wet gully is designed as a lifting gully. The conversion is done by inserting a suction hose through the outlet to the channel and sealing between the hose and the outlet fitting. The hose ends in the gully about 10 cm above the bottom of the gully sump. This increases the retention of dirt and, in the case of the Hebergully, causes the deposits in the sewer to be remobilized by means of interval loading.

2. New construction or renovation with earthwork measures.
The lifting gully is used in the separation system, with the lifting device being connected to the waste water channel. The lift gully should be used in the separation system, especially in busy streets and in postures with deposits. In order not to unduly increase the proportion of extraneous water, the hold-up gully is used in all other cases. A lifting gully should generally be used in the mixing system. Table 1 shows the renovation variants with the gully types that can be used sensibly.

Table 1: Renovation concept

Water protection through drain gullies

The dirt retention through Hebergullys increase in the separation system depending on what already exists Gully type from 10% to 30% to 30% to 40% of the total Dirt. This part of the dirt mainly contains Sediments that would settle in the water bed. Deposits on the river bed, provided that they are not within approx. 7 days as debris to be transported to one partial to complete death of the biocenosis on the sole cause or cause long-term damage. In the mixing system is due to the constant reduction of channel deposits the rinsing potential of rain overflows by 20% to 40% the annual overflow freight reduced. Since this is the same is a significant reduction in sediments similarly positive effect with regard to water protection in the separation system.

Cleaning the drainage system

The effort for cleaning of the drainage system is reduced when it is introduced the gully in two ways. The maintenance effort at cleaning of the lift gully is reduced since only 1 or 2 times a year the sludge buckets have to be emptied the more complex cleaning of the wet gully with the help of a vacuum truck. Only in the event of a blockage of the jack as a result a defective or missing sludge bucket or too long intervals between the lifts is a more time-consuming maintenance of the gully required. However, the lifter can be lockable flap can be simply rinsed in the lifter arch, see above that this rarely required maintenance is carried out quickly can. Furthermore, considerable savings will be made in the Cleaning of the channel postures can be recorded.

Claims (9)

1. gully with a drain for a drainage in the mixing system, as well as with an inlet with an associated sludge bucket, and with a gully body with a lower bottom, characterized in that the drain is formed by a lifting tube ( 70 ) which is formed by the gully body ( 48 ) is guided to the outside ( 68 ) and ends within the gully body ( 48 ) just above the bottom ( 50 ), and that the bottom ( 50 ) of the gully ( 78 ) is closed and forms a gully sump ( 66 ) ( FIG. 6 ). 2. Gully according to claim 1, characterized in that the lifting tube ( 70 ) ends about 5-10 cm above the bottom ( 50 ). 3. Gully according to claim 1 and / or 2, characterized in that the lifting tube ( 70 ) outside the gully ( 78 ) is designed as an odor trap ( 72 ). 4. Gully with a drain for a drainage in the mixing or separation system, and with an inlet and a gully body with a closed bottom to form a gully sump, the drain being arranged above the closed bottom in the gully body, characterized in that the drain is a throttle ( 58 ) with a throttle opening ( 60 ) is formed ( Fig. 5). 5. Gully according to claim 4, characterized in that above the throttle opening ( 60 ), a hold-up ( 62 ) is provided through which the wastewater rising above the throttle opening ( 60 ) can escape through the outlet ( 56 ) without being affected by the throttling effect . 6. gully, with an inlet, a gully body with a closed bottom to form a gully sump, and with a first drain located above the bottom in the gully body, characterized in that the first drain is designed as a throttle ( 58 ) with a throttle opening ( 60 ) is that a second drain is provided, which is formed by a lifting tube ( 70 ) which is led out through the gully body ( 48 ) and ends inside the gully body ( 48 ) just above the bottom ( 50 ), that in the lower region of the gully body ( 48 ) a gully sump ( 66 ) is formed, and that a sludge bucket ( 38 ) is arranged below the inlet ( FIG. 4). 7. Gully according to claim 6, characterized in that the lifting tube ( 70 ) ends about 5-10 cm above the bottom ( 50 ). 8. Gully according to claim 6 and / or 7, characterized in that the lifting tube ( 70 ) outside the gully ( 54 ) is designed as an odor trap ( 72 ). 9. Gully according to one or more of the preceding claims 6-8, characterized in that above the throttle opening ( 60 ), a hold-up ( 62 ) is provided through which the wastewater rising above the throttle opening ( 60 ) without being impaired by the throttle effect the drain ( 56 ) can escape.