You can find here the information about
sewerage system of Grodno, pollution sources and polution monitoring.
They are fragments from graft report “Assessment of GRODNO City Sanitation System
Technical and Financial Proposals for Improvement of Works and Practices”.
This report has been prepared by the Halcrow/BCEOM Consortium in the frame of Reducing Agricultural and Industrial River Pollution: Improving Surface Water Quality in the Neman River Basin, Grodno Oblast, Belarus in 2002.
Background and objectives
The water quality monitoring network for the Neman river includes two stations close to the city of Grodno. One is located one kilometre upstream from the city. Another is located ten kilometres downstream from the city, just downstream of the Grodno wastewater treatment plant.
The change in the values of a number of parameters between these stations indicates that the city of Grodno City is a significant pollution source for the Neman river in Belarus.
The population of Grodno City is around 300,000. Most houses and industries (as far as these do not directly discharge to the surface water themselves) are connected to the municipal sewerage system.
The industrial activity has reduced since 1992. There are still two big factories (Azot, producing fertilisers and Bellegprom, producing synthetic textile fibres) with their own treatment plant discharging into the Neman river. Most others are connected to municipal sewerage system. However, there is little quantitative information on pollution sources and the respective loads of different types of sources (industries, WWTP, storm water …) responsible for the decrease in water quality in the Neman river around the city of Grodno.
The Project aims to reduce industrial and agricultural river pollution. The report in question will contribute to this objective by:
1) Estimating the real impact of the city of Grodno on the Neman river,
2) Determining as accurately as possible the load distribution of identified potential pollution sources:
The urban wastewater treatment plant,
The various industrial wastewater treatment plants,
Direct discharges (domestic and industrial),
Storm water,
Overflows from sewers; and
Diffuse and agricultural pollution.
3) Proposing a programme for overall improvement of works and practices, concerning all sanitation systems.
WASTEWATER TREATMENT PLANT ASSESSMENT
The total design capacity should be 142,000 m3/day and the real capacity close to 110,000 m3/d.
Main process:
Screening, Sand traps, Pre-aeration tank, Primary treatment, Aeration tanks, Secondary settling tanks
Final treatment:
Final treatment is disinfection by chlorination. The disinfection is done in two contact tanks.
Sludge treatment
Primary and excess sludge is pumped from the treatment plant to the sludge lagoons on the opposite (left) bank of the Neman river.
The sludge lagoons, which cover 210 ha, were put in place in 1969 on the left bank of the Neman river near the village of Berezhany in 4 cascades. Lagoons are 1.5 to 3 m deep with a volume of about 5.5 thousand m3. Dry sludge is dumped into a quarry nearby.
Concentration of mixed liquor is very low to get pumping and treatment easier. Compartments are working alternatively for drying and removing sludge.
The outlet effluent is collected and goes back to the treatment plant through a gravity pipe and a pumping station.
There is no specific watertight layer (clay, PEHD, concrete …) in the lagoons and infiltration protection is provided by sludge layers only. This situation is very hazardous for the (ground-water) resources, which can be easily polluted by heavy metals.
Treatment efficiency
Efficiency on carbon pollution is good. Expected efficiency for medium loading biological treatment is 90 percent. Nevertheless, BOD5 outlet concentration is higher than MAC (2000 results).
TSS rate is also higher than MAC because of sludge feeding in the outlet effluent.
Efficiency for NH4 treatment is better than expected. A medium loading biological treatment is not supposed to eliminate more than 20 to 25 % of ammonium nitrogen. Outlet NH4 concentrations are just under MAC. Because of the low efficiency for NH4, few NO3 are generated.
Oil products treatment efficiency is enough. Inlet concentrations are already low.
Efficiency for P04 and heavy metals is essentially the result of the primary treatment stage.
Sludge lagoons
The banks of the lagoons and the distribution system are not properly maintained. Some lagoons overflow the banks. . The sludge has a high content of heavy metals.
The sources of this high heavy metal pollution are mainly the electroplating industry, the Grodno tannery, TORGMASH, fine-cloths factory,
Dried sludge dumped on the ground is washed away by rain. The risk for feeding heavy metals and other toxics to the river is very high.
According to the average inlet BOD5 load (20 t/day), theoretical sludge production of the wastewater treatment plant should be more than 20 t/day (dry matter). Annual theoretical production is then close to 7,500 t/year. If the dry matter content of the “dried” sludge extracted from lagoons is 35 percent, it is corresponding to 20,000 m3 of removed sludge in a year.
There is no data on dried removed sludge.
Wastewater Treatment Monitoring
Flow measurement
There is no flow measurement working on the treatment plant. Flow meters are out order since 2000/2001.
The volumes used for loads calculation are estimation for previous data and consumed water.
It is estimated that the daily flow volume is between 110,000 and 140,000 m3/day, with an average of 125,000 m3/day.
Sampling and analysis
Single samples are taken every day at each step of the process.
Sampling on peak flow and maximum daily concentration is not representative. Results are nevertheless used with estimated volumes for load calculation.
Most of laboratory was provided when the treatment plant was built (1968). Part of it is outdated and not working.
The accumulated uncertainty is very high and could be as high as 30 percent!
INDUSTRIES
Connected factories
Thirty-three main factories are connected to the municipal sewer. Twenty of them treat their effluent before discharging into municipal sewers.
All industrial plants need a licence for discharging into the municipal sewers. This licence gives allowed volumes and concentrations, according to standards coming from a directive issued by the Grodno executive committee and based on the “regulations of receiving wastewater from industries into municipal sewerage system”.
Industrials are under obligation to do daily self-monitoring. In reality such monitoring hardly takes place
Three levels can exercise control:
Vodokanal,
Oblast Committee of Natural Resources and Environmental Protection,
Ministry of Health.
Draining industrial wastewater into municipal sewers with levels of pollutants in excess of standards level occurs quite frequently. In such cases, higher taxes are paid for sewage.
The estimated volume discharged by those main factories (data from Vodokanal) is 22.0 million m3/year. According to the annual volume carried to the wastewater treatment plant, the industrial part should be 56% of the total flow which is 39.5 million m3/year.
There is no specific and regular data concerning discharged loads from industries, especially for heavy metals. It is not possible to determine the industrial part in the collected pollution load.
Unconnected factories
Seven factories are not connected (including the two main factories, Azot and Bellegprom) and discharge their treated or untreated effluent in the Neman river. According to meteorological conditions and heating and lighting needs, activity is higher in warm season than in cold season. Discharged volumes can be quite different.
Azot
This factory produces fertiliser. It is located upstream of Grodno, on the right bank of the river.
Water is supplied from boreholes. A biological treatment plant designed for 37,595 thousand m3/year treats the wastewater. Treated effluent is then pumped into lagoons for a final treatment. Lagoons are just near the municipal sludge lagoons, downstream Grodno.
In average, 18,000 m3/year are discharged in the Neman. Pollution load is 46 tonnes/year for BOD5 and 4.5 tonnes/year for NH4.
Bellegprom (textile factory)
This factory elaborates synthetic textile fibres. Water is supplied from boreholes. Wastewater is treated by a physical treatment plant designed for 1,305 thousand m3/year.
In average, 400 m3/year are discharged in the Neman. Pollution load is 1.5 tonnes/year for BOD5 and 0.1 tonnes/year for NH4
IDENTIFIED POLLUTION SOURCES
Only two main discharges have been identified :
Wastewater treatment plant outlet,
• The main industrial discharge : Azot.
Other pollution sources are qualified as “diffuse pollution” which includes :
• Agricultural discharge (directly in the Neman and in tributaries),
• Unconnected households and industries,
• Storm water outlets.
Data are not reliable enough to determine proportion in pollution sources. It is plausible that this proportion is close to :
50 % from municipal wastewater treatment plant and Azot lagoon,
50 % from other pollution sources which can be called “diffuse pollution”.
SOURCES OF POLLUTION IN GRODNO CITY AND IMPACT ON THE NEMAN
Global impact on Neman river
There is following monitoring date for 1998/2001 10 km downstream variations (concentrations in mg/l)
N-NH - 40.42
BOD - 54.5
TSS - 23.2
Oil.prod – 0.05
N-NO3 - 0.79
N-NO2 - 0.034
pH - 8,4
SO4 - 19,9
PO4 - 0,2
Cl - 16,9
Grodno City impact on the Neman river quality can be approached from upstream to downstream in four main parameters : BOD5, NH4, Bacteriology and heavy metals.
It is also possible to use the WPI classification to get a global quality profile of the river.
BOD5
BOD5 comes from all organic matters (not only from human activity).
BOD5 concentrations are rather low in the Neman, most of the time less than 5 mg/l. Analysis accuracy is less than 20% for these values. Low variation of BOD5 does not allow to draw significant conclusions.
Upstream concentrations are from 1,5 to 6,5 mg/l with an average at 3,6 mg/l (2000 and 2001 data). Downstream from 2 to 7 mg/l with an average at 4,5 mg/l.
In the average year (river discharge = 6,5 million m3/day), the BOD5 annual load upstream Grodno should be 25,000 tonnes. The downstream annual load is close to 30,000 tonnes/year. From this it can be calculated that the contribution of Grodno is about 5,000 tonnes per year from which 900 come from the urban wastewater treatment plant and the Azot factory together.
A 1 mg/l error on BOD5 analysis (20 % of 5 mg/l) is close to 5,000 tonnes/year (as much as the contribution of the city of Grodno and much more than the emission of the WWTP).
With such low concentrations, BOD5 cannot be considered as a good parameter for monitoring the river and assess Grodno city impact on the Neman.
NH4
NH4 only comes from humans and animals (and small amounts from industry eventually). Analysis accuracy is good and reproducible.
Upstream Grodno city, the average concentration is 0,1 mg/l. Upstream wastewater treatment plant and Azot lagoons discharges concentration is 0.2 mg/l. Downstream those discharges, it is 0.5 mg/l. Ten kilometres downstream, concentration is going down to 0.4 mg/l.
On average, the NH4 annual load downstream of Grodno is 650 tonnes. Immediately downstream Grodno (but upstream the WWTP), annual load is 1250 tonnes/year. The difference (650 tonnes) comes from all pollution sources in Grodno (unconnected areas, overflows from sewers, industries, etc...). Downstream WWTP and Azot discharge, load is 3250 tonnes. 400 of them come from the two main discharges (Azot, and wastewater treatment plant). Diffuse pollution seems to be more important than identified pollution sources.
NH4 is one of the main deterioration factors for the Neman River, just downstream those discharges.
Ten kilometre downstream WWTP, part of NH4 has been oxidised by self-purifying power of the river and the concentration reach exactly the limit.
Bacteriology
The requirement for bathing water is less than 5000 TC (total coliforms) /100 ml.
From available data (21 for 2000/2001) upstream Grodno concentration is between 60 and 24,000 TC/100ml. 12 results are under the limit and 9 are above.
High values are generally observed by summer time when people use the river for recreation.
From other data (1 result in February 2002) the concentration upstream the wastewater treatment plant is 24,000 TC/100 ml, and 70,000 TC/ml after WWTP discharge. This tendency is confirmed by verbal conversation from the Health Inspectorate in Grodno.
Heavy metals
Impact of Grodno City cannot be proved for heavy metals, as the concentrations in the Neman river are most of time below the detection limit.
Only Zn and Fe can be detected, with concentrations higher than the maximum allowed concentrations, already upstream from Grodno City. For those parameters, the river is not affected by crossing the study area. They are the same downstream.
Those significant concentrations come from natural water quality due to geological composition of soil in the catchment area.
CONCLUSIONS
Monitoring
It seems that around the city of Grodno there are enough monitoring stations on the Neman river, which are properly situated. Sampling is unfortunately not performed in winter and does not permit to study real monthly variations.
There is no monitoring on sewers, except on industrial discharges, which are controlled only by taking single samples for analysis. Loads are calculated through water consumption. This way for monitoring is not representative.
Industries do not respect daily self-monitoring obligations.
What is done in the treatment plant cannot be considered as monitoring.
Average data provided are only mathematical averages from single samples. Volumes are only estimated from water consumption. Loads are then always calculated from estimated volumes and concentrations. Using such inaccurate data can lead to mistakes in the monitoring process.
Wastewater treatment plant
Vodokanal everyday maintenance is good and efficient. Outlet concentrations often seem to respect guidelines. Hundred percent of total effluent is generally treated by the wastewater treatment plant.
Available primary settling capacity is 20% higher than the secondary capacity, even if the standard required is twice the primary settling capacity for the secondary stage.
The Secondary settling stage actual hydraulic capacity is the main limiting parameter (even after finishing the new tank presently under construction). The design capacity is approximately 75 to 85,000 m3/d, depending on the distribution in the tanks. After finishing work on the last secondary setting tank, capacity should be close to 100,000 m3/d.
Inlet effluent is very diluted, essentially because of high level of domestic consumption. The wastewater treatment plant can treat 65 to 70 percent of the total average volume actually received. To treat all the emitted BOD5, it is necessary to reduce water consumption from 300 to 200 litres per day and per person.
There is apparently also dilution with clear water (take-up of water supply leaks and groundwater from wet lands) which can represent 15 to 20 percent of the total inlet flow.
The WWTP only efficiently treats carbon pollution, which is not the main priority to maintain water quality and not to affect ecological balance, considering the dilution in Neman river.
The WWTP is not designed to treat nitrogen pollution. Efficiency for NH4 is less than 50%.
The final treatment is not reliable enough and might be environmentally hazardous according to chlorine compounds resulting of chlorination.
Global efficiency of WWTP against toxic substances (heavy metals,…) is not enough to preserve water quality, but is enough to contaminate sludge which cannot be used in agriculture.
Most of the metallic equipment is to be replaced; same for electric motors (cabinets), most of the pumps (worn by sand) and air injection units.
Monitoring (flow, sampling, laboratory,…) and automatic regulation equipment is required.
Although it seems possible to easily improve wastewater treatment plant reliability, efficiency will always be limited by design in a medium load activated sludge biological treatment.
The main impact of Grodno City sanitation system on the Neman River can be observed in dry season where the river flow is low and water is used for recreation.
The low flow measured in summer in the Neman River is around 85 m3/s. The average flow for the wastewater treatment plant is 1.5 m3/s. This discharge is then only 2 percent of the total flow downstream of Grodno. The dilution of the wastewater treatment outlet in the river is around 50 times.
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