Proposal by Russia to delete hot spot 18.2

Transcription

1 Proposal by Russia to delete hot spot Hot spot Central Aeration Station 2. Location 1, Bely Island, St. Petersburg 3. Reasons for designation of hot spot Discharges of phosphorus higher than requirements 4. Reason for hot spot deletion 4.1. Technical specifications of Central Aeration Station (CAS) Central Aeration Station was put into operation: 1 st phase in 1978 ( m 3 /d), 2 nd phase in 1985 ( m 3 /d) of design capacity 1,500,000 m 3 /d. Design treatment parameters : SS < 15 ; BOD tot < 15. Flow rate per second in dry weather: average 17.4 m 3 /s, design 20 m 3 /s, in rainy weather 30 m 3 /s. If flow rate of 30 m 3 /s ( m 3 /h) is exceeded, the excess wastewater is discharged via emergency gate (throughput capacity 28,000 m 3 /h) located in receiving chamber. WWTP layout Main pump station has 9 pumps: 5 FV-14-6/58 pumps (FV 21600/58) of 6 m 3 /s capacity and 4 ZOFV-13 pump aggregates (FV9000/63) of 2.5 m 3 /s capacity, 4 mechanical screens (100mm) for the protection of pumps from coarse matter and clogging. Wastewater pre-treatment: 13 grates (6 mm). The solids trapped by the grates are taken to a landfill. Upon that, wastewater goes to 12 horizontal sand traps (4800 m 3 ). Design flow rate of wastewater in sand traps is m/s. Sand is removed by hydraulic elevators to sand grounds. Once mineralized on sand grounds, the sand is used for CAS surfacing. Mechanical treatment Following pretreatment wastewater goes to 12 primary radial settlers (54m in diameter and 5.3m deep). Settling time at design flow rate is 2.3 hours. Sludge from the primary settlers is filtered at 2mm grates, treated at hydrocyclone and pumped to sludge dewatering stage. Biological treatment: 12 aeration tanks that comprise pre-anoxide, anaerobic, 1 st aerobic, anoxide and 2 nd aerobic zones that provide for biological removal of phosphorus, nitrogen and organic impurities. Treatment time in aeration tank at design capacity m 3 /h is 5.4 hours. Sludge mix from aeration tanks goes to 12 secondary radial settlers where active sludge is settled, settling time being 2.3 hours. Settler scrapers are designed for continuous operation. Sludge treatment. Excess active sludge is thickened at 4 sludge thickeners (33m). Solid matter content in thickened sludge is 2.5%. The mixture of raw sludge and thickened sludge at % moisture content is fed to sludge treatment phase where it is filtered at mechanical grate (2 mm). Separated sludge goes to sludge receiving tank. Following that, the sludge goes to dewatering phase, the tank with 2 mixers. Mixed sludge is dewatered at 10 centrifuges using polymer flocculants (6 kg/t of dry matter). Design capacity to trap solid particles is 96% at 70-75% moisture content of dewatered sludge. The effluent is fed to CAS receiving chamber. Dewatered sludge tank is used when operation is stopped (total volume being 160 m 3 ). page 2 of 6

2 The cake from the centrifuge is unloaded into the hopper via which it is pumped by Schwing КSР piston pumps to incinerator via 8 injectors located in a circle around the furnace. Sludge is pumped by 2 pumps via four pressure lines to one incinerator. Sludge incineration. The major Pirofluid incineration technology is incineration of dewatered sludge in quartz sand fluidized bed furnace. Incineration phase comprises 4 furnaces. Incineration furnace is a metal structure 12m high that consists of two cylinders one above the other and connected with each other. The lower 4.5m cylinder is a blow chamber, the upper 7.5m cylinder is a reactor. The blow chamber and the reactor are separated with selfbearing arch of fire bricks wherein air nuzzles are inserted. 37 tonnes of quartz sand (30% fine, 50% medium and 20% coarse) is fed on the arch via injector. Fluidization air that is burning air at the same time is fed to the blow chamber following pre-heating to С in recuperator with flue gases. From the blow chamber air via nozzles goes to sand layer and fluidizes it. Sand layer temperature is maintained at С. The organic matter of the sludge is oxidized by excess oxygen and turns into gaseous products of burning, while the mineral matter is taken away by flue gases as ash. Ash generated by sludge burning is landfilled Measures implemented to meet requirements, including the implementation of the best available technologies and environmental practice. CAS aeration tanks were updated to reach required nutrient level through total nitrogen removal and biological treatment of phosphorus to meet requirements. Anoxide (denitrification processes), anaerobic zones (phosphates removal) and aerobic (oxidation of ammonium nitrogen) were made. Such design and technology adjustments allowed to meet requirements in Considering special role of phosphorus in the eutrophication of the Gulf of Finland, Vodokanal management decided to reduce phosphorus to 1.0 and later to 0.5. Biological treatment is not enough to reach such parameters. In this respect John Nurminen Foundation and Plancenter (Finland) offered to use chemical coagulation and settling of phosphates using Fe 2 (SO 4 ) 3 Ferix-3 agent produced by Kemira. The agent was tested and applied: to effluent, to sludge prior to dewatering, to internal sewer, to sludge mix prior to secondary settlers and to wastewater prior to primary settlers. The highest effect was reached when Fe 2 (SO 4 ) 3 was added to wastewater prior to primary settlers. Chemical settling of phosphorus in primary settlers Ferix-3 continuous dosing started in November 2008 via distributed channels of primary settlers. Optimum reagent dosage is 35 g/m 3. Chemical settling of phosphates results only in partial of concentration at primary settlers output. The major part of phosphates is removed from wastewater in aerobic zone of aeration tanks. The key factor for maximum phosphates removal is maximum phosphates release in the anaerobic zones of aeration tanks and sufficient amount of dissolved oxygen in the aerobic zone for the consumption of phosphates by phosphorus accumulating microorganisms Capital investments CAS reconstruction cost is 58.2 million. Operation tests for chemical settling of phosphorus at CAS have terminated now. Chemical reagent dosing installation is being installed. The project is carried out under the bilateral cooperation between Russia and Finland. Total project cost is 288,536. John Nurminen Foundation supplied equipment worth 57, 900. page 3 of 6

3 Total phosphorus contncentrations, Концентрация фосфора общего, мг/л 4.4. Monitoring data on pollutant discharges during last four years Average concentrations in 2008 at CAS output were: BOD 5 4.6, total nitrogen 9.0, total phosphorus 0.8. The chart below illustrates pollutant concentrations in terms of total phosphorus at CAS input and output in Phosphorus concentrations at CAS input and output in Концентрация фосфора общего на входе и выходе ЦСА в гг 5 4,5 4 3,5 3 2,5 2 1,5 1 0,5 0 4,7 4,4 4 4,1 4,2 1,9 1,5 0,96 0,77 0, г г г г 9 months 2009г( месяцев) P tot at input фосфор общий вход,мг/л P tot at output фосфор общий выход,мг/л page 4 of 6

4 5 Analysis of WWTP operation for compliance to Recommendation 28Е/5 Wastewater treatment (> 100,000 PE) ) Year BOD 5 N tot. Р tot. % requirements % requirements % requirements ) or 80% or 70-80% or 90% months ) requirement to be reached not later than 31 December page 5 of 6

5 6. Programmes of monitoring and control of pollutants Control of treated wastewater discharges is done in accordance with the document The procedure for departmental control of WWTP operation, wastewater composition and the impact thereof upon hydrochemical regime of water body. The procedure for CAS control Sampling point WWTP input WWTP output Wastewater outlet into Neva estuary in the Gulf of Finland, 500m radius area Sampling method Automatic sampler Manual sampler Sample type Daily average Single Single Sampling frequency Daily, each 2 hours Once in ten days Once in 30 days Once in ten days Once in a month (August- October) Parameters рн, suspended matter, ash content in suspended matter; phosphates phosphorus; ammonia nitrogen; nitrate nitrogen; nitrite nitrogen; COD Total nitrogen; total phosphorus; dry residue; ash content in dry residue; copper; total iron; nickel; zinc; mercury; aluminium; manganese; surfactants; phenols; chlorides BOD tot. Temperature; oil products; dissolved oxygen; coliphages; helminths eggs ; pathogenic micro flora Temperature, рн; odour; colour; COD; BOD 5 ; suspended matter; dissolved oxygen; total nitrogen; total phosphorus; oil products; helminths eggs; coliphages; pathogenic micro flora; manganese; iron; mercury. page 6 of 6

6 Additional information concerning Municipal Sub-Hot -Spot 18.2 Central Station Aeration (CSA) Area population >100,000 people Assessment of CSA operation compliance with Recommendation 28E/5 Municipal Wastewater treatment BOD5 P total N total Month % requirements % requirements % requirements January February March April May June July or 80% or 90% or 70-80% Reduction Reduction Reduction August September October November December Mean page 7 of 6

7 Area population >200,000 people Assessment of CSA operation compliance with Recommendation 28E/5 Municipal Wastewater treatment in 2009 year Recommendation 28E/5 will enter into force in December 2012 BOD5 P total N total Month % requirements % requirements % requirements January February March April May June July or 80% or 90% or 70-80% August Reduction Reduction Reduction September October November December Average 4, page 8 of 6

8 Assessment of CSA operation compliance with Recommendations superseded by Recommendation 28E/5: 9/2 concerning measures aimed at the of discharges from urban areas by the use of effective methods in wastewater treatment ; 16/9 Nitrogen removal at Municipal sewage water treatment plants. BOD5 P tot. N tot. Year % Recommendation 9/2 % Recommendation 9/2 % or 90% Recommendation 16/ % , page 9 of 6