Vacuum system to eliminate direct discharge into the Gulf of Finland
Vacuum sewerage system – energy efficient and environmentally friendly solution for the water discharge network, installed in the Toriki village located in the Krasnoselsky district of St. Petersburg.
Solution to which problem
The Toriki village is a part of the Gorelovo municipal district (population: 32 436), located in the Krasnoselsky district of Saint Petersburg. The territory is characterized by a high level of groundwater and flat terrain. Due to the fact that when designing a traditional gravity sewage system, its indicators (flow rate, slopes, diameters) conflicted with the specified regulatory requirements, a vacuum sewage system was provided in the village.
This solution has several advantages:
- the ability to divert domestic wastewater to treatment facilities and improve the environmental situation in the territories and adjacent water bodies, where the untreated wastewater of the village was previously discharged,
- creating a comfortable living environment for people,
- increasing the investment attractiveness of territories,
- saving resources during construction by reducing the amount of work, especially in limited spaces (shallow depth, small diameters of pipelines) and operation due to low power consumption of the system.
Technical conditions
The Toriki village is located in the Leningrad Region and has the following main characteristics that influenced the choice of a vacuum sewerage system:
- Smooth and flat terrain;
- High level of groundwater;
- The existing development of the territory with low buildings in which there is a partial or complete absence of sewerage systems;
- Lack of places for laying traditional drainage systems with a high depth of installation and standard slopes to ensure that the networks are not clogged;
- Significant fluctuations in wastewater discharge associated with seasonal fluctuations in water consumption;
- Discharge of insufficiently treated or untreated wastewater to the terrain and water bodies;
- Possibility of small energy consumption for the operation of the sewerage system.
Implementation
The vacuum sewerage system Roediger® can be installed as an autonomous and independent system, or can be integrated into the existing water treatment network.
The external vacuum sewerage system in the Toriki village is provided from receiving chambers, to which sewer outlets from subscribers are connected, underground vacuum pipelines with a diameter of 90 to 250 mm and a vacuum pumping station with at least one vacuum tank.
The receiving chamber consists of a receiving tank with a capacity of 50-350 liters, in which a certain volume of domestic wastewater is accumulated (at least 25% of the daily rate), and a control chamber (clean unit), with a vacuum valve, a level sensor and a pneumatic relay (a device that controls a vacuum valve). Reception of domestic wastewater from the gravity pipeline of the internal sewerage system into the external vacuum sewerage system is carried out using a vacuum valve, which is located in a clean block of the receiving chamber.
When the household wastewater discharged from the house outlet into the receiving chamber reaches a predetermined level, the vacuum valve closed up to this point is pneumatically opened. The wastewater is sucked from the receiving chamber into the main vacuum pipeline due to the pressure difference between the atmospheric pressure in the receiving chamber and negative pressure 25-60 kPa in the vacuum line. After emptying the collecting chamber, the vacuum valve closes again.
The underground vacuum pipeline is manufactured in accordance with the design documentation from HDPE-100 polyethylene pipes of SDR-11 class in accordance with GOST 18599-2001, joined by the electric-welded pipe connector. The wastewater is transported through an underground vacuum pipeline in the direction of the vacuum pumping station at a speed of 2-4 m/s. The connection of the vacuum pipeline from the receiving chamber to the main line is performed at an angle of no more than 55o. The vacuum pipeline is connected directly to the vacuum reservoir of the vacuum pumping station, in which a vacuum of 60-70 kPa is maintained with the help of vacuum pumps.
Depending on the capacity of the vacuum system, the range of pipe diameters, in accordance with the calculations in the design documentation, varies from 90 to 250 mm. For control and adjustment of the pipeline system, control nozzles are installed on the main line every 100 m. The filling level of the vacuum tank at the vacuum pumping station is automatically controlled by the transfer sewer pumps. When the level of wastewater in the tank reaches a certain level, sewage pumps are automatically connected and the wastewater is removed to the sewer collector or to a treatment plant.
System maintenance
The maintenance schedule of the installed system highly depends on the individual operating conditions, f.ex. high dust concentration in the air or mechanical impurities in water might require maintenance performed more often. The following intervals are recommended with the initial parameters.
Weekly: Check the oil level. Check the machine for oil leaks. If found, carry out the necessary repairs (contact Aqseptence Group).
Monthly, if an inlet filter is installed: Check the filter cartridge, replace if necessary.
Every 2000 hours, no later than after 6 months: Change oil, oil filter and exhaust filters
Every 6 months: Clean the machine from dust and dirt. If a gas ballast valve is installed – clean the valve filter.
Every 5 years: Carry out a major overhaul of the machine (contact Aqseptence Group).
Result
The use of vacuum sewerage systems in the Toriki village allowed:
- to use low labor costs (high level of automation, availability of a control system with the possibility of transmitting information to the control room, the turbulence of the flow eliminates sedimentation of sludge);
- to obtain a drainage system with high energy efficiency (receiving chambers are energy-independent, the only consumer is the vacuum station);
- to ensure high environmental safety (no leaks and pollution of groundwater, during transportation the sewage is saturated with oxygen, which excludes the possibility of the development of anaerobic processes, the load on the treatment plant is reduced).
This system ideally "fits" into the city highways for laying networks and made it possible to intercept all direct outlets of the existing drainage system with the direction of wastewater to a single treatment plant before being discharged into a reservoir.