Project 1. Hot Spot Smolensk Municipal Vodokanal

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10.2. Project 1. Hot Spot Smolensk Municipal Vodokanal

10.2.1. Description of the Facility

Characteristics of Municipal Wastewater Treatment Facilities

The muncipal wastewater treatment facilities, which was refurbished in in 1987, are characterised by old systems, obsolete equipment, equipment in poor repair, energy-inefficient  equipment and poor control of the operating system.

Wastewater Treatment and Discharge

Mechanical and biological treatment of wastewater is carried out by four (4) wastewater treatment facilities, which, in total, treat approximately 48,910 thousand m³/year of wastewater.  Sanitary wastewater and industrial effluents are directed to the wastewater treatment facilities.  After purification, the treated wastewater meets established standards.

The main issues associated with the operation of the wastewater treatment facilities are as follows: worn equipment, an inefficient aeration system, and a poorly equipped operating control system.  In order to improve the treatment process, it is necessary to install a new aeration system and construct improved sludge stabilization systems. 

The population of Smolensk is about 353000 people, with 257690 residing in apartment housing which is connected to the sewerage system.  The wastewater sewage generated by 92000 inhabitants of the town is collected in septic tanks and transported to the wastewater treatment facilities, while the remaining 3000 inhabitants use local means (toilet pits without any equipment).

The main sewerage wastewater treatment facilities process communal wastewater and industrial effluents, whereas the other three units of wastewater treatment facilities treat mainly the discharges from urban residential districts.

In the town of Smolensk there are approximately 50 industrial enterprises connected to the main wastewater treatment facilities.  These include food processors and electronic industries; approximately 20 enterprises have their own local wastewater treatment facilities.  The pre-treatment of industrial effluents typically uses the most standard methods, including chemical and various coagulation technologies.

Industrial Effluents

According to the data used for calculation of load in 2001 the volume of discharges of industrial effluents made up approximately 13778,0 thousand m³.  Flow measurement was carried out by industrial enterprises themselves, that is why the accuracy of these measurements is not perfectly reliable.

Budget Establishments

Budget organizations consume and discharge 3109 thousand m³/year.

Sanitary Wastewater from the Residential Area

According to the data given in the water supply section, water consumption of the population is approximately 24370 thousand m³/year.  95000 people are not connected to the centralized sewerage system.  According to the Smolensk Vodokanal datta, houses, which are not connected to sewerage system, consume about 90 l/person/day, which makes up 3302 thousand m³/year and generate about 110 l/person/day of wastewater.  The total incoming volume of sanitary wastewater to the major wastewater treatment facilities is 27672 thousand m³/year.

Stormwater Runoff make up 6000 thousand m³

At present, Smolensk municipal vodokanal has 4 sources of stormwater discharge to the Dnipro River.

The major part of sewerage system was built or reconstructed during the last thirty years.  The pipes are made of ceramics, steel, cast iron and transite.  The trunk sewer line is concrete.

More than 200 km of pipelines are made of ceramics.  Ceramics pipes do not undergo corrosion and mechanical wear, but they are sensitive to uneven soil settlement.  Due to insufficiently hard ground, the pipe damage occurances are not rare.

About 11 km of the pipes are made of steel.  They do not have a covering and their service life is short.

Sewage Pump Stations

There are 21 sewage pump stations in the town of Smolensk; it should be noted that they have rather high output.

There is mechanical rake in front of the pumps at 7 of the pump stations; all of the others are equipped with screen facilities (lattice cells are 16 mm).

The oldest pump station was built in 1947 and is in poor condition.  The other operating pump stations were constructed in the period between 1972 and 1993.  Three of them are are operating overload conditions.

The main pump station was constructed in 1982.  There station has a vibrational problem, which has led to the weakening of the girders of the building.  The vibration is produced by the pumps and is exacerbated by the weak building structure.

Rayons of City of Smolensk with no Sewerage System

At present about 92000 people live in the rayons where there is no sewerage system.  In these rayons wastewater is collected in cesspits or septic tanks.  Sediment from cesspits or septic tanks is taken to the wastewater treatment facilities.

Wastewater Characteristics

In 2001, the BOD load was 12410 ton/year.  The share from industry was 6205 ton/year.

In 2001, the total nitrogen load was stable, approximately at the level of 2000.  The share from industry was 692 ton/year.

The total phosphorus load was 292 ton/year.  The share from industry was 36 ton/year.

The concentration of heavy metals in the incoming wastewater for treatment is low.  Usually storm water from the urban territories is the reason of high concentration of zinc and copper, whereas high chromium content is accounted for industrial sources.  This indicates that industry can have strong impact on the quality of wastewater.  However the adverse impact of industrial effluents on main sewerage wastewater treatment facilities seems low; there are no signs of the biological processes being depressed.

In order to meet these standards, it is necessary to take the necessary steps toward the construction of local wastewater treatment facilities at industrial enterprises of the city which are the sources heavy metal entry.

Table 10.1 presents the average peak data at the point of entry into the Smolensk municipal wastewater treatment facilities.

 

Table 10.1 : Pollutants at the Entry of Municipal Wastewater Treatment Facilities of Smolensk

 

Assessment of Operational Efficiency

The standards as for BOD₅, suspended solids and heavy metals in the treated wastewater are exceeded.

Phosphorus discharge is lower than the temporary standard for treated wastewater.  In order to reach the national standard, it would be necessary to introduce a dephosphorization process.

The content of most salts of heavy metals is decreased approximately by 70%.  However, the low content of salts of heavy metals in treated wastewater provides for accumulation of these salts in the sludge.

Description of Technological Process and Parameters of Main Wastewater Treatment Facilities

Mechanical Processing

Approximately 20% of the wastewater is directed to Line 1.  Processing includes three screen facilities (lattice cells are 16 mm).  Then the wastewater is directed to two screening facilities where sand is separated out.  The two primary clarifiers are the final stage of mechanical processing.  The crude sediment from Line 1 along with sludge from Line 2 are pumped over for the subsequent treatment.

The flow to Line 2 makes up approximately 80% of the total incoming volume of wastewater to the main sewage wastewater treatment facilities.

Crude sediment along with the activated sludge are repeatedly directed to the primary clarifies of Line 2.  The entire excess sludge (apart from crude sediment in Line 1) is extracted from these tanks.  The excess sludge has a standard concentration of approximately 2% of dry substance.

Aeeration Tanks

After mechanical processing the wastewater is directed to the aeration tanks for aeration.  Every tank is divided into four sections with a total length of 400 meters.  The first 25% of the aeration tanks areused for the regeneration of activated sludge.  The next 50% are used for the aeration of the dispersed supply of wastewater and the last 25% - for the aeration of total mixture of wastewater and sludge.

Aerators are located uniformly along the length of tank with the exception of the first fourth (the zone for sludge regeneration), where there is only one pipe on each side.  In the course of examination the aerators were tested by sight and it was ascertained that they produce small and well-dispersed air bulbs along the whole length of pipes.

The air is distributed with the help of four superchargers, which are operated by switching on/off.  The rate of aeration is regulated by the level of excess oxygen in aaeration tanks.  The value of excess oxygen is determined by laboratory analysis.

Secondary Settling Tanks

Secondary settling takes place in three settling tanks.  The system for processing of the excess and recycled sludge includes four pumps with an output 2500 m³/hour each.  Usually two pumps are activated.  The pumps are linked up to one 800 mm pipe for the recycled sludge and to a 250 mm pipe for the excess sludge.  The link between the excess and recycled sludge is regulated by pressure loss in the pipes.

Sludge Processing

Crude sediment and excess activated sludge are removed from the primary clarifiers to the sediment processing system.  The sediment processing system consists of two sediment compactors, three hydrocyclones, six centrifuges for dehydration and three aerobic mineralizers for fugacity.

Treated wastewater in the town of Smolensk is discharged to the Dnipro River.  Data concerning water quality in the Dnipro River upstream and downstream of the main sewage wastewater treatment facilities prior the discharge and after the discharge of wastewater are given in Table 10.2.

Table 10.2 : Water Quality in the Dnipro River Upstream and Downstream of Main Sewage Wastewater Treatment Facilities in 2001

 

10.2.2. Description of Mitigation Measures

In order to ensure that the the level of pollution in the waste-water is redueced, it is necessary to realize the capital measures presented in Table 10.3.

Table 10.3 : Environmental Measures for Smolensk Municipal Vodokanal for 5 years

 

Investment Programme

Total costs of realization of the aforementioned measures would be 68700 thousand roubles.  For the Phase 2 facilities the cost would be 25400 thousand roubles.

Further to the above environmental measures, the reconstruction programme includes:

- Construction of a new main sewerage pumping station in the value of 48230 thousand roubles;

- Reconstruction of the mechanical treatment system at the cost of 48291 thousand roubles;

- Inspection and reconstruction of the sewerage system – 134490 thousand roubles.

The total investments would amount to 342 mln. roubles, including 94100 thousand roubles for the first five years.

10.2.3. Feasibility Analysis

The economic assessment of water-protective measures was carried out by means of comparing the economic results of these measures with the costs required for their realization.

For Smolensk Vodokanal, the following input data was used:

·                     The cost of reconstruction of the treatment facilities (for five years) is 94100 thousand roubles;

·                     The savings in the operation costs as a result of the reconstruction would be 7080 thousand roubles;

·                     The respective input data and calculation sheets are presented in Annex 3.

 

Calculation of mono-pollutant (М).

М = _i * V_i = 3356 c. t (see the calculation table)

 

Per year, М_a = 671 t

D_a = 8400 * 1.8 * 671 = 10146 thousand roubles

 

Calculation of incremental lost financial benefit I:

I is assumed in professional judgment as 10% of D_a = 1015 thousand roubles

Calculation of the economic result of the water-protective measures

E_wp = 10146 + 1015 = 11161 thousand roubles

 

Calculation of the reduced costs:

DC = Е * К + Т_c,

Е = 0.12

К = 94000 thousand roubles

Т_c – operational costs of the wastewater treatment (based on the data from Vodokanal) will be reduced by 7080 thousand roubles

DC = 0.12 *  94000 + (-7080) = 11280 – 7080 = 4200 thousand roubles

 

Calculation of the net annualized economic effect:

DU = E_wp - DC = 11161-4200 = 6961 thousand roubles

 

The pay-back period (Т) for the investment into water-protective measures will be:

Т = К / DU = 94000 / 6961 = 13.5 years

 

Table 10.4 : Reduction in the Total Mass of Mono-Pollutant to be Achieved in Pollution with Wastewater from Treatment Facilities of City of Smolensk Within Five Years

The cost of averted damage which would have been caused by pollution of the water body, including the incremental cost of lost economic benefit was accepted as economic result of water-protective measures.

 

Table 10.5 :  Discharged Pollutants, caused Damage by Calculation Years, and Investments

 

The cost of damage averted as a result of realized mitigation measures will make up 10146 thousand roubles.  The lost financial benefit exceeds 1000 thousand roubles.

Discounted costs will make up 4200 thousand roubles, net economic effect – 6961 thousand roubles.

The pay-back period in water-protective measures will make up 13.5 years.

An effective payback of investments into wastewater treatment facilities is 14 and less years.

The Smolensk Municipal Vodokanal Hot Spot is the promising enterprise to be included in the list of projects considered favourable for investment.