ROMAG

Combined Sewer Overflow Screen-RSW

STORMWATER TREATMENT

The contamination of surface water resources by combined water from overflow systems and partly also from stromwater tanks, consists of all the solids which are present in the waste water. This involves a very wide range of dissolved, semi-dissolved, fiber and solid substances with different structures and specific weights (plastic strips, sanitary towels, diapers, condoms, faecal matter, paper etc.).

A basin-screen combination is the best way of meeting the criteria in such cases. In this concept, retention of the heavily contaminated flushing surge is the main task of the basins. On the other hand, the screen removes light, floating and solid substances which would otherwise contaminate the outfall area

ROMAG CSO Screens (Combined Sewer Overflow) 

ROMAG specializes in the development and manufacture of screens for overflow structures. For many years they have been collaborating with professional experts from the water resources sector and have therefore acquired extensive experience and references both at home and abroad.

The Combined Sewer Overflow screen has the following typical features:

• high operational reliability
• automatic mechanical cleaning
• corrosion-resistant design
• robust construction
• low-maintenance requirement
• narrow bar spaces (4mm)
• controlled handling of the screened material

Design Features

ROMAG combined sewer overflow screens are designed to a modular system. All types consist largely of elements which can be put together to obtain the most suitable type of screen for each particular application. The robust frame structure holds the screen grate, the cleaning carriage with the comb stacks and the hydraulic or pneumatic cylinder.

The screen grate is built up from pre-tensioned narrow screen bars. The small bar cross-section ensures optimum use of the screen area, low screen resistance and high flow capacity. The standardized bar interval is 4mm, so that all the undesirable floating materials are retained.

One or more cleaning carriages are arranged on the outflow side depending on the screen length. They travel in guides over the screen surface. The comb stack which is mounted on the cleaning carriage engages in the screen grate, supports and guides the screen grate bars. The comb stack accordingly replaces the transverse stiffener elements which are undesirable in water cleaning systems. The screen cleaning is switched on and off as a function of the level. Drive is normally hydraulic.

RSW- Screen with Horizontal Throughflow

Features

- low-cost solution
- simple structure
- easy access to screen
- low head loss

Benefits

• dispenses with the need to make high investments in retaining capacity volume
• prevents unnecessary contamination of the receiving water courses
• is safe and reliable to operate
• permanently performs mechanical cleaning action
• is resistant to corrosion
• is rugged
• requires little maintenance
• has a small bar spacing (4 mm)
• transports the caught material from the inlet zone
• materials either 316L or 304L

Function

The combined sewer overflow screen RSW, fitted vertically between the discharge culvert and the relief sewer, reliably retains all visible solids when the excess water flows through. Water flows horizontally through the screen. It is mounted on the owner`s prepared concrete sill. The height of the sill depends on the hydraulic survey and is lower than the required water level when relief operations start. The retaining panel attached to the rear side of the screen is designed to achieve a uniform screening rate but so that a CS of max. 1.50 m/s is not exceeded. The upper edge of the screen is designed as an emergency spillway. The water is discharged via the screen if the cleaning system fails (e.g. in the event of electrical power failure) or if overloaded.

Design Combined Sewer Overflow RSW Screen

The ROMAG combined sewer overflow screen RSW consists of a rugged frame made of stainless steel sections. The horizontal screen bars are braced in this frame. The cleaning carriage which is moved to and fro by a double-acting hydraulic cylinder is located on the rear side. Several comb rows of asymmetrical triangular shape move through between the screen bars. The water flowing through forces the caught material against the bars where it is moved on by the cleaning combs with their ``steep end`` longitudinally. The flow direction assists this movement. During return travel, the ``flat end`` of the combs slides through beneath the caught material. The traverse paths and shapes of the combs are intermatched so that each cleaning comb transfers the caught material to the next cleaning comb. It is slid to the end of the screen and is then discharged with the outflowing effluent to the sewage treatment plant. This prevents a problematic concentration of caught material at the inlet end.

System Planning

The combined sewer overflow screen RSW has proven successful in several hundred applications. However, close cooperation with the offices and agencies involved is necessary in order to achieve a reliably operating installation. This is necessary in order to determine and comply with the hydraulic boundary conditions. This concerns a streamlined feed to the combined sewer overflow screen and the discharge to the sewage treatment plant with the required downgrade:

- The caught material which is transported by the screen to a defined point must move continuously downwards into the discharge path. For instance, a shaft for the caught material may need to be used depending on local conditions.

Combined Sewer Overflow Screen-RSW-K

Features

• optimal usage of the existing storage volume
• substantial reduction of number and quantity of the discharges
• best possible protection of your receiving waters

Benefits

• optimum utilisation of available storage volume
• dispenses with the need to make high investments in retaining capacity volume
• drastically reduces the number of relief operations
• prevents unnecessary contamination of the receiving water courses
• allows reliable quantity measurements
• has an increased efficiency when subject to part load
• is safe and reliable to operate
• permanently cleans mechanically
• is corrosion-resistant
• is rugged
• requires little maintenance
• transports the caught material from the inlet zone
• materials either 316L or 304L

Function

The combined sewer overflow screen RSW-K, fitted vertically between the discharge culvert and the relief sewer, reliably retains all visible solids > 4 mm when the excess water flows through horizontally. It is mounted on the owner`s prepared concrete sill. The height of the sill depends on the hydraulic survey. Type RSW-K is a combination of Type RSW and a controlled weir wicket, but the basic functions of the CSO screen are identical. The relief height can now be controlled on Type RSW-K with a control function. The weir wicket is controlled by two hydraulic cylinders. The aim of the control function is to discharge as little contaminated rainwater as possible into the relief sewer.

This works as follows: In basic position, the weir wicket is closed, i.e. no effluent or waste water can flow into the relief sewer. If the water level at the inlet end has reached a predetermined height, the weir wicket starts to open. level probe which allows various level heights to be measured generates the signal. An optimum position of the weir wicket then corresponds to each signal. This achieves minimum discharge into the relief sewer. Cleaning is also performed by the cleaning carriage analogously.

Quantity measurement option: A second level measurement system at the relief end and the fact that the position of the weir wicket is known by the displacement measurement system allows the relief rates to be detected, totalled and recorded permanently.

Design of the Combined Sewer Overflow RSW-K Screen 

The design of the RSW-K is identical to that of the RSW in the screen area. The same components are used. A rugged, moving weir wicket is attached by means of hinges and tight metal side panels in place of the static retaining panel. An all-round seal on the carrier frame of the CSO screen ensures tightness at three sides when the weir wicket is closed. When open, the weir wicket seals against the lateral guides. The weir wicket is driven by two control cylinders which move synchronously swing to the incorporated displacement measuring systems. The anchoring system of the control cylinders is integrated in the frame structure. The structure itself is thus not loaded additionally.

When the control cylinders are fully extended, the hydraulically calculated maximum angle of the weir wicket is reached. This prevents overloading of the screen surface owing to an excessively low relief height.

System Planning

Combined sewer overflow screen RSW-K has already proven successful in very many applications. However, close cooperation with the offices and agencies involved is necessary in order to achieve a reliably operating installation. This is necessary in order to determine and comply with the hydraulic boundary conditions.

This concerns a streamlined feed to the combined sewer overflow screen and discharge to the sewage treatment plant with the required downgrade:

• The caught material which is transported by the screen to a defined point must move continuously downwards into the discharge path. For instance, a shaft for the caught material may need to be used depending on local conditions.

Combined Sewer Overflow Screen-RSO

Features

• no head loss on inflow side suitable for installation in existing structures

Benefits

• dispenses with the need to make high investments in retaining capacity volume
• prevents unnecessary contamination of the receiving water courses
• is particularly suitable for subsequent installation behind an existing sill
• thus minimises loss of volume in the basin owing to the rake
• is safe and reliable to operate
• permanently performs mechanical cleaning action
• is resistant to corrosion
• is rugged
• requires little maintenance
• has a small bar spacing (4 mm)
• transports the caught material from the inlet zone
• materials either 316L or 304L

Function

The combined sewer overflow screen RSO, fitted horizontally between the discharge culvert and the relief sewer, reliably retains all visible solids when the excess water flows through. Water flows vertically from top to bottom through the rake, which is mounted between the prepared concrete sills. The height of the combined sewer overflow screen depends on the hydraulic survey and is lower than the required water level when relief operations start. The anticipated flow rate depends on the resultant retention height and the weir height selected on the basis of the conditions at the inlet end. The water is discharged via the concrete sill (emergency relief) if the cleaning system fails (e.g. in the event of electrical power failure) or if overloaded.

Particular importance has been attached to operating safety and reliability. The first step towards this relates to omission of components susceptible to failure such as limit switches. In addition, the electrical hydraulic control elements are arranged outside the critical zone so that only two hydraulic pipes lead into the wet chamber. The clever design means that the combined sewer overflow screen cleans itself constantly. In the event of solid material causing brief clogging, the control system is designed to repeat the comb movement at this point until the rake is unobstructed again.

On this ROMAG concept, the caught material is transported from the rake area into a caught material shaft at the end of the screen area. This means that the caught material is no longer floated onto the screen surface, which is important when heavily loaded. This shaft is emptied via a controlled gate valve or by means of a pump back into the sewage treatment plant inlet. Continuous emptying of the shaft during rake operation is recommended, depending on the size of the caught material shaft and quantity of caught material.

Design of the Combined Sewer Overflow RSO Screen

The ROMAG combined sewer overflow screen RSO consists of a rugged frame made of stainless steel sections. The vertical rake bars are braced in this frame. The cleaning carriage which is moved to and fro by a double-acting hydraulic cylinder is located on the underside. Several comb rows of asymmetrical triangular shape move through between the rake bars. The water flowing through forces the caught material against the bars where it is moved on by the cleaning combs with their ``steep end`` longitudinally. During return travel, the ``flat end`` of the combs slides through beneath the caught material. The traverse paths and shapes of the cones are intermatched so that each cleaning comb transfers the caught material to the next cleaning comb. As the water level drops, transport of the solids towards the caught material shaft is assisted by special flaps. The caught material is slid into the caught material shaft at the end of the rake. This ``disposal`` of the solids also prevents a problematic concentration of caught material at the inlet end.

System Planning

The CSO screen RSO has proven successful in many applications. However, close cooperation with the offices and agencies involved is necessary in order to achieve a reliably operating installation. This is necessary in order to determine and comply with the hydraulic boundary conditions.

This relates to streamlined feed to the CSO screen and discharge to the sewage treatment plant with the required downgrade:

• shape and volume of the shaft are crucial to smooth operation of the installation.
• this also applies to handling of the caught material transported by the rake into the shaft. It will generally depend on many project-specific parameters as to whether the caught material is transported from the shaft towards the sewage treatment plant after or already during the event.

Combined Sewer Overflow Screen-RSU

Features

• suitable for installations with low space in height
• outflow and emergency overflow possible on both sides
• ambitious regarding water flows and maintenance

Benefits

• dispenses with the need to make high investments in retaining capacity volume
• prevents unnecessary contamination of the receiving water courses
• is safe and reliable to operate
• permanently performs mechanical cleaning action
• is resistant to corrosion
• is rugged
• requires little maintenance
• has a small bar spacing (4 mm)
• transports the caught material from the inlet zone
• materials either 316L or 304L

Function

The combined sewer overflow screen RSU, fitted horizontally between the discharge culvert and the relief sewer, reliably retains all visible solids when the excess water flows through. Water flows vertically from bottom to top through the screen which is mounted on the owner`s prepared concrete sills. The height of the CSO screen depends on the hydraulic survey and is lower than the required water level when relief operations start. The anticipated flow rate is dependent on the resultant retention height and the weir height selected on the basis of conditions. The water is discharged via the concrete sill (emergency relief) if the cleaning system fails (e.g. in the event of electrical power failure) or if overloaded.

Particular importance has been attached to operating safety and reliability. The first step towards this relates to omission of components susceptible to failure such as limit switches. In addition, the electrical and hydraulic control elements are arranged outside the critical zone so that only two hydraulic pipes lead into the wet chamber. The clever design means that the combined sewer overflow screen cleans itself constantly. There is no cross-bracing which could lead to build-up of caught material in the screen area at the inlet end. In the event of solid material causing brief clogging, the control system is designed to repeat the comb movement at this point until the rake is unobstructed again.

On this ROMAG concept, the caught material is disposed of from the rake area into a caught material shaft and guided near to the bottom. This means that the caught material is no longer floated onto the screen surface, which is important when heavily loaded.

Design of the Combined Sewer Overflow RSU Screen

The ROMAG combined sewer overflow screen RSU consists of a rugged frame made of stainless steel sections. The horizontal rake bars are braced in this frame. The cleaning carriage which is moved to and fro by a double-acting hydraulic cylinder is located on the upper side. Several comb rows of asymmetrical triangular shape move through between the rake bars. The water flowing through forces the caught material against the bars where it is moved on by the cleaning combs with their ``steep end`` in longitudinal direction. The flow direction assists this movement. During return travel, the ``flat end`` of the combs slides through beneath the caught material. The traverse paths and shapes of the combs are intermatched so that each cleaning comb transfers the caught material to the next cleaning comb. It is slid to the end of the rake and is then discharged with the outflowing effluent to the sewage treatment plant. This prevents a problematic concentration of caught material at the inlet end.

System Planning

The CSO screen RSU has proven successful in many applications. However, close cooperation with the offices and agencies involved is necessary in order to achieve a reliably operating installation. This is necessary in order to determine and comply with the hydraulic boundary conditions.

This relates to streamlined feed to the CSO screen and discharge to the sewage treatment plant with the required downgrade: System planning

• • the caught material which is transported by the rake to a defined point must move continuously downwards into the discharge to the sewage treatment plant. One good solution is to use a caught material shaft.
• particular attention must be paid to the space conditions in the inlet area. Excessively constrained inlet sections aggravate or render impossible the inspection and maintenance work which is required periodically.

Combined Sewer Overflow Screen-RSS

ROMAG`s combined sewer overflow screens normally operate horizontally and require an installation length of at least 3 m. They are thus unsuitable for many, less recent structures with small or narrow spillway openings.

The new RSS combined sewer overflow screen with raised screen has been designed for opening widths of 40 to 120 cm respectively for structures characterised by cramped conditions. Apart from operating vertically, everything else functions in precisely the same way as on the well known ROMAG combined sewer overflow screen which have been used very successfully for many years now and which enjoy an excellent reputation on the market. The RSS is designed for flow rates of 80 - 300 l/s. 

England and Ireland with their many small storm water relief tanks and basins are particularly interested in the RSS. During the course of a series of tests covering several months, a water and sewage authority in Britain`s north-east determined that the RSS retains 95 % of the solids and suspended matter > 6 mm in the relief water. The first RSS has already been sold to Spain.

POLYTHERM® Belt Drier

Field of applications include

• molasses from the foodstuffs
• fodder
• cosmetics industries
• slurry from the cosmetics and soap industries- sludge`s from agriculture, communal and industrial effluents.
• products and by-products in powder form or forms similar to powder from industrial processes such activated carbon, waste products from tea and coffee production and coated broken repulped particles from the paper industry etc.

The resultant products leave the evaporation chamber with a dry substance content of 80 to 99%, which can be adjusted, depending on further processing.

Simply Technology

The pre-dewatered material whose water content varies depending on the properties of the relevant product to be dried is pumped by a feed pump through a heat exchanger into the loading unit of the patented POLYTHERM® belt drying system. The material to be dried is fed from the cutting mechanism through the output opening onto the high-grade steel mesh belt. Rotating blades which periodically close off the exit openings output the product in the form of individual, pressed pellets or in the form of a sort of pressed granulate. Opposite to the high-grade steel mesh belt, there are several heating elements along the belt conveyor, distributed between the input device and an unloading lock through which the dried material leaves the drier.

Dust-Free Drying

By contrast with conventional belt driers, the POLYTHERM® belt drier operates with infrared radiation. An appropriately tight array of heating tubes which are heated so that they emit in the infrared band in the area specified forms a high-temperature zone. The heat is issued at this point by the heating tubes in the form of radiation and convection. This abruptly forms a crust on the surface of the material to be dried. Drying is performed by convection in the downstream area.

Closed Process Air Circuit System

In a closed process air circuit, the air at the downstream end of the high-grade steel mesh belt is ducted into the drying chamber and flows through the chamber in a direction opposite to the direction in which the material to be dried is conveyed. As it passes through the drying chamber, the air is heated and saturated with moisture originating from the material to be dried. The air leaves the drying chamber on the upstream side.

No Odours

The process air ducting system now routes the hot air, saturated with water, to the condenser. The air is then cooled and the condensate is routed to the drainage pipe. The air which is now cool again is routed through a further fan to the flue gas heat exchanger. There is an additional fan, used to feed fresh air into the process circuit, if required between the fan and the flue-gas heat exchanger.

Profitable Technology

Fast flow through: The dwell time of the product in the evaporation chamber depends on the speed of the conveyor belt and the length of the POLYTHERM® belt drier. It is between 8- 15 minutes depending on product and required final dry substance content. Evaporation of the water escaping from the material to be dried occurs at a slight partial vacuum. This eliminates the possibility of vapour emission from the plant.

Modular Construction

Individual system sections, such as the drying chamber, may be arranged one on top of the other or side-by-side and may be combined so as to produce a drying system with several drying lines.

View plan summaries.

Efficient Use of Energy

It goes without saying that the walls of the POLYTHERM® belt drier features an exothermic thermally insulated design to supply additional heat loads with heat.

Control

The system is controlled with MIPOS® (Modular integrated process control and optimisation system).

Minimal Labour Coasts

The drying system which has a mechanically simple design requires a sophisticated measurement and control system, in particular if different products are to be processed with the same system.

MIPOS® incorporates control intelligence in a PC. All variable operating parameters are controlled on a personal computer running under the Windows NT® operating system.

Variable Input Products

The system integrates a system database, linked to a knowledge database and an automatic operator. This means that MIPOS® is aware of all changes made manually and, at a later point, can signal these deviations to the user, display to the user corresponding proposals for adjustment of the corresponding operating parameters or correct the parameters itself if an identical or similar situation occurs subsequently.

Optimised End Product

Thanks to the combination of MIPOS® and POLYTHERM® belt drier, it is possible simultaneously to optimally achieve different, required specifications of the material to be dried. The following parameters can be set, amongst others, depending on how the material to be dried is to be used:

- length of the pellets
- diameter of the pellets
- shape of the pellets
- density and strength of the pellets

When drying sewage sludge, liquid manure and manure etc., working with drying temperatures of over 200°C achieves complete disinfection of the output material. The advantage: Both work steps, disinfection and subsequent drying, are performed in one operation. This allows the operator to save on the expense of a disinfection system.