Construction of Molodezhnoye WWTP with modern membrane wastewater treatment technologies
In December 2018, the construction of wastewater treatment plant with implemented membrane technology and a capacity of 2,500 thousand m3/day was completed in Molodezhnoye settlement of the Kurortny district of St. Petersburg. The plant was designed for the population equivalent of 11,000 PE (7,800 PE based on the calculation of BOD5 load).
Solution to which problem
Previously Molodezhnoye wastewater treatment plant belonged to the “Chernaya Rechka” resort and was designed to receive and treat 500 m3 of wastewater a day. Untreated wastewater was discharged into the Smolyachkov stream, thus negatively affecting the resort and the Gulf of Finland area environment.
The project was implemented in the Kurortny district of St. Petersburg in the Molodezhnoye settlement. The Molodezhnoye WWTP construction provides the prospective development of the infrastructure of the Molodezhnoye, Smolyachkovo and Serovo settlements.
The facility is equipped with sewage regulators in order to regulate the hourly and daily unevenness of wastewater inflow from the Kurortny catchment area.
Wastewater firstly passes screening grits for crushing of mechanical impurities, and then it is pumped to combined mechanical treatment facilities, including 2 mm gap screens, a sand and grease chambers. Next, wastewater enters a highly loaded aeration tank for biological treatment with enhanced removal of nutrients by nitrification-denitrification technology. Aluminum sulfate dosing as chemical treatment stage is applied for intensification of phosphorus removal. Mixed liquor after the aeration tank is transported to membranes facility.
Treated wastewater is supplied to ultraviolet disinfection facility, and then discharged to the Gulf of Finland by gravity discharge duct.
Introduction of ultrafiltration membranes enables enhanced wastewater treatment in conditions of the flow instability in terms of temperature and rates specific to the resort area.
1. Wastewater sludge treatment technology
Two screw presses are provided for the excess sludge dewatering. The process outputs are reject water and cake. Reject water is discharged into the on-site sewer and then goes to the beginning of the treatment line. Cake is collected in a container for dewatered sludge, and subsequently is transported to the sludge incineration plant of the Northern Wastewater Treatment Plant.
2. Treatment of polluted air generated during wastewater treatment.
All open surfaces of the sewage regulators system are equipped with removable overlaps and an air intake system for odorous gases from under the overlaps, as well as from all installed equipment that contacts with wastewater. Discharged odorous gases are transported to gas treatment facilities, where they are treated and released into the atmosphere. The sorption-plasma-catalytic purification of gas emissions and biofiltration technologies are used for the gases treatment. The applied gas treatment systems minimize the negative impact of gaseous substances generated during wastewater treatment and provide favourable living conditions for residents of the Kurortny district of St.Petersburg.
3. Full automation of technological processes and control over the operation of process equipment.
Following the full treatment cycle, wastewater is discharged into the Gulf of Finland through a deep-water outlet at a distance of 1,200 m from the coastline, thus ensuring comfortable resort environment for citizens and development of infrastructure for the residents of Molodezhnoye, Smolyachkovo and Serovo settlements.
Usage of the membrane ultrafiltration technology allows high-quality treatment of wastewater in the specific conditions of the resort hosting sanatoriums and youth health camps: with unstable hydraulic and pollutants load.
Modern wastewater and sludge treatment methods with automatized high-tech equipment help to significantly improve the environmental state of the Kurortny district in St. Petersburg.
The process solution allowed to reduce the treatment plant footprint by half compared with the conventional technology (which is also relevant in the resort area). Membrane bioreactor replaces two process stages (separation of activated sludge and treated water instead of a secondary sedimentation tank and tertiary treatment of suspended solids) at the Molodezhnoye WWTP.
Molodezhnoye WWTP indicators, mg/l