Dry well pumping station with solids separation
Dry well pumping station with solids separation
Dry well pumping stations are designed to pump a specified volume of sewage to a designated height and distance within a set time. Unlike pump stations, pumping plants utilise a system that separates solid contaminants from sanitary sewage. This solution offers numerous benefits, such as lower operating costs and more comfortable working conditions for the operators.
Benefits of use
Separation of solid contaminants – increases the efficiency and reliability of the system, allowing for the use of higher-efficiency pumps (impellers with smaller free passage).
Reduced risk of failure – separating solids before they reach the pumps reduces the number of potential impeller blockages.
Improved operating conditions – pumps and the pumping stations module are housed in a dry enclosure, making maintenance and repairs easier.
Elimination of unpleasant odours – a sealed retention chamber with ventilated odour neutralisation completely eliminates odours.
Prevention of sewage stagnation – optimal retention capacity prevents the formation of odours.
Easy and hygienic operation – no contact with sewage and easy access to pumps and valves increases safety and user comfort.
Lower operating costs – high-efficiency pumps enable the use of motors with lower power, reducing operational expenses.
Corrosion resistance – high-quality materials provide corrosion resistance, and the pumping plants come with a 5-year warranty.
Wide range of pump selection – pumps are selected according to project specifications and customer requirements.
Application
Dry well pumping station can be used in any sewer system, particularly recommended for:
- areas, where the terrain is varied,
- areas with low population density,
- residential and industrial estates located a significant distance from the sewage discharge point,
- urban agglomerations.
Types of dry well pumping station
ETS II dry well pumping station with solid pollutant separators
The ETS pumping plant contains two single-channel solids separators located outside the retention module at the pump discharge nozzles. This allows quick access to the separator’s interior for inspection. The separator’s design allows it to handle sewage inflow of up to 50 m³/h.
A typical ETS II dry well pumping station consists of a body, a pumping module with separators, pumps, hydraulic equipment, an automation system, and optionally, remote control. ETS II sewage pumping plants comply with EN 12050-1:2001, bear the CE mark, have a national technical assessment issued by ITB, and are marked with the B construction mark.
Their main advantages include:
- the ability to service the technological components of one of the two inflow circuits while the dry well pumping station is in operation,
- quick and easy service access to all technological components – pumps, separator, flexible separator flaps, check and shut-off valves, distributor, inflow pipeline,
- the application of pumps from any manufacturer, individually selected based on project specifications or according to user requirements.
Operation Principle of the ETS II Pumping Plant
Sewage flows through the inflow collector to the distributor, from where it is directed to two separate inflow circuits. The specially shaped distributor minimises the risk of clogging, and inspection windows ensure effective monitoring. The sewage then moves to the separator, where solids (screenings) are trapped by flexible straining flaps. The purified sewage flows into the retention chamber, and the sewage containing solids remains in the separator chamber. When the maximum sewage level in the retention chamber is reached, one of the pumps is activated, and the sewage is pumped out towards the receiver along with the impurities from the separator. This mode of operation is repeated cyclically, and the pumps operate alternately.
ESS dry well pumping station
The ESS dry well pumping station contains two dual-channel solids separators, equipped with flexible strainer flaps. The separators are located outside the retention module at the pump discharge nozzles. Each ESS pumping plant is equipped with a bypass system, consisting of a bypass pipe, pneumatic gate valve, and compressor.
The ESS pumping station has a module made of stainless steel. Due to the dual-channel separator design, it is suitable for handling very high sewage inflow rates, operating at up to 360 m3/h.
Comparison of dry well pumping station types
| ETS II | ESS | |
|---|---|---|
| Inflow intensity | up to 36 m3/h | up to 250 m3/h |
| Type of separator | single-channel | single-channel |
| Type of sewage | sanitary | sanitary |
| Separator location | outside module | inside module |
| Retention module material | stainless steel | stainless steel |
| Body material | concrete / polymer concrete / HDPE | concrete / polymer concrete / HDPE |
| Piping material | stainless steel | stainless steel |
| Bypass flow | none | above 50 m3/h |
| Piping diameter | DN100 | DN100 – DN250 |
| Pump operation | alternating | alternating |
| Number of pumps | 2 | 2 or 3 |
| Pump protection level | IP 68 (option IP 55) | IP 68 (option IP 55) |
Construction and installation
Basic elements of dry well pumping station construction:
Body
The body of the device is a sealed tank made from concrete, polymer concrete, or HDPE, tailored to the client’s needs, soil and water conditions, and investment requirements. The cover of the pumping station has an opening equipped with a stainless steel, HDPE, or cast iron manhole cover, depending on the intended use of the site, where the dry well pumping station is located. The dimensions of the manhole openings are adjusted for the installation and removal of pumps and for operational and service purposes. Transitions through the body walls are made watertight to a degree that prevents the infiltration of groundwater and the exfiltration of sewage.
Retention Module
The retention module of the pumping station is a sealed tank designed to accumulate sewage flowing into the device. It is entirely made of stainless steel or HDPE. The materials used eliminate the need for additional anti-corrosion coatings and ensure long service life. Its size and retention capacity are calculated during the design selection process, considering the intensity of sewage inflow to the dry well pumping station. The upper part has inspection hatches that allow for inspection of the interior during operation, as well as full service and cleaning of the interior when the retention module is completely emptied, and the inflow of sewage to the pumping station
is stopped.
Solids Separators
Solids separators are made of stainless steel. Each separator is equipped with flexible straining flaps. Depending on the type of dry well pumping station, two kinds of separators are used. In ETS pumping station, single-channel separators located outside the retention module are used. In ESS and ESS-PE dry well pumping station, dual-channel solids separators located inside the retention module are used. In both cases, separators are situated at the discharge ports of the pumps. Each type of separator features a simple design that ensures a full free passage during pumping, without any permanent elements in the flow of pumped liquid that could block the flow of sewage. The construction and operation principle of the separator ensure its self-cleaning during pump operation.
Pumps
Dry well pumping station have pumps that are mounted vertically outside the retention module. They are not directly immersed in the sewage, unlike in traditional pumping stations. Typically, submersible pumps with a cooling jacket and an IP68 protection rating, adapted for “dry” operation, are used. Pumps installed in a sewage pumping plant are equipped with a channel or Vortex impeller. Pumps in dry well pumping station are designed for alternating operation in a 1+1 setup. Each of the pumps operates in alternating cycles, with a performance equal to the total output of the pumping station at the set lifting height. The pumps serve as a reserve for each other.
Hydraulic valves
Fixtures:
In pumping station produced by Ecol-Unicon, spherical check valves and knife gate valves, from well-known and widely available manufacturers, are used. These are placed outside the retention module, ensuring ease of service and quick access to replaceable parts. They facilitate operational and maintenance activities, while the device is running.
Backflow Fixtures:
- Elbow spherical check valves – located on both gravity inflow pipelines behind the distributor, before the solids separators. The operation system of the elbow valves is fully automatic.
- Straight spherical check valves – located on each of the dry well pumping station risers.
Cut-off Fixtures:
Knife valves – used to cut off the flow of sewage by closing the conduit aperture. They are positioned in strategic locations to allow servicing of individual equipment components (fixtures, pumps).
Standard additional equipment:
- CE-marked descent ladder,
- handrails,
- drainage installation,
- lighting,
- mechanical-gravitational ventilation ensures continuous air exchange inside the body. The retention module is equipped with gravitational ventilation, finished with an odour neutraliser. The neutralisation process uses impregnated activated carbon, constituting the filling of the chimney-type odour neutraliser.
- power and Control System – a standard piece of equipment in each dry well pumping station is a power and control switchboard, which has a CE certificate, confirming compliance with the 2014/35/EU and 2014/30/EU directives.
The primary task of the switchboard is the automatic activation of pumps depending on the level of sewage in the pumping station. Level measurement is performed using a hydrostatic probe. The punping station is also equipped with two vibratory probes, serving as additional safety sensors that enable the automatic operation of the plant in case of failure of the hydrostatic probe. It is possible to monitor and control the parameters of the plant by connecting it to the Bumerang superior monitoring system – data transmission is carried out wirelessly, using the GPRS standard.
Piping
Constructed from corrosion-resistant materials – stainless steel or HDPE. The diameter of the piping is adjusted according to the intensity of the sewage flow in the pumping station.
Operation
Dry well pumping station are automatic devices that do not require constant operation and frequent maintenance. The device should be subjected to a detailed technical inspection.
Due to the diverse composition of sewage, the frequency of inspections should be determined individually – at least once a year. Maintenance of pumps and electrical devices should be performed in accordance with the manufacturer’s documentation. The first inspection should be conducted within six months of commissioning the device, and subsequently under normal device load once a year. Failure to perform inspections in accordance with the manufacturer’s recommendations will result in the loss of warranty.