Identification of the Greater Baku wastewater systems on hydraulic modelling basis using GIS

 

Dr.I.Mamedzadeh, S.Nimer

 

Montgomery Watson / Azspetsprominvest Consulting Engineering Co.

54 Bulbul Avenue, Baku City, Azerbaijan, 370014

phone : (99412) 957056; fax : (99412) 951247; e-mail : ats@aspi.baku.az

 

 

Abstract

For Baku city (capital of Azerbaijan) with a population of some 1.9 million an enormous wastewaters are evident in the discrepancy between the volume potentially available and the actual quautity of water received by users.

In Apsheron peninsula as the larger urban area one third of the population is not connected to a municipal wastewater system. All of the Greater Baku urban centers have inadequate sewerage and lack treatment facilities. Large number of different sewerage systems together with new settlement are creating a difficulties for effective monitoring of wastewater collection and treatment.

The study area, Apsheron peninsula, consists of wastewater connected and non-connected to the collection system, treated or untreated primarily to the Caspian Sea, inter- connections with the stormwater drainage system, pass directly to storage Bulbul and GunliGel lakes. Due to this complexity it is unable to study individual discharge points and some parameters such us capacity, leakage and infiltration, pumped flows, wastewater loads, within short period without to use modelling methods.

In this context relevant wastewater features have been hydraulic analysed to extract spatial parameters related wastewater production and the extrated parameters are used input for GIS to obtain different wastewater needs.

 

Keywords: wastewater, sewerage, modelling, CCTV survey, classification, assessment

 

Introduction

Greater baku with area about is 2192 km2 situated to western part of the caspian Sea. At present, more than 70% of industrial potential of Azerbaijan is concentrated in the Apsheron peninsula, mostly in two big cities - Baku and Sumgait.

The population presently connected to the collection system is about 78% of population of Apsheron peninsula. The total wastewater is reported to be nearly 1.3 million m3/day, as the capacity of operational treatment plants is only 0.95 million m3/day.

A main objective of this study is to use approach the hydraulic modelling for assessment the existing physical condition of the various wastewater system components and expend the system to meet present and future wastewater needs. In this context an attempt has been made adopt a new methodology called Hydroworks, developed by «Wallingford Procedure» for determination of hydraulic capacity of the wastewater collection system.

 

Current Situation

The wastewater systems serving the Greater Baku area comprise some 1100 km of

trunk, collector and local sewers, 22 pumping stations, 100 km of pressure mains and five wastewater treatment plants.

The Baku City has a number of treatment facilities, mainly for the treatment of domestic sewage in the volume of 317 million m3 (Hovsan biological treatment facilities with a capacity of 600,000 m3/day and with a project capacity of 940,000 m3/day; Haji Hasan mechanical treatment facilities - 18,600 m3/day; Shuvalan mechanical treatment facilities - 18,600 m3/day ; Zikh mechanical treatment facilities - 126,000 m3/day; Karadag biological treatment facilities - 17,600 m3/day; Khatai mechanical facilities with total capacity 258,400 m3/day). The construction of the Greater Baku sewerage system was started in the 1970's, was planned to be finished in 1980.

However, so far it operates at 60 % of the capacity. Provision of a sewerage system for half of the settlements and districts of Baku has not yet been completed.

About 400,000 m3 of untreated wastewater is discharged primarily to the Caspian Sea through by passes or inter-connections with the stormwater drainage system. Some flows pass directly to Apsheron lakes, which are periodically pumped into the wastewater collection system as constantly rising levels have led to flooding nearly of properties.

 

Field Survey

In order planned investigations to expand the sewerage systems it is essential that the existing facilities are analysed to assess: size, level, capacity and performance; structural condition and residual life; service condition including siltation, internal surface encrustation and blockages; adequacy, serviceability and performance of mechanical and electrical equipment.

The physical conditions of the Baku wastewater collection system has been investigated by conducting a Closed Circuit Television (CCTV) survey of a number of representative sample sewers. The survey provided information on the internal surface and structural condition of a selection of sewer pipe materials, integrity of pipeline joints, vertical/horizontal displacements, blockages and sediment depths, levels of infiltration or inflow. The 381 surveys (survey is two or more length of sewer surveyed in a continuous operation, while sewer length is the distance between pipe-end faces in consecutive manholes) represent 17,522 m of pipelines, the actual length of surveyed pipe is 13,685 m. For classification of the internal pipe condition were defined five following grades : (1) Acceptable structural condition; (2) Minimal collapse risk in the short terms, but potential for further deterioration; (3) Collapse unlikely in the near future, but further deterioration likely; (4) Collapse likely in the foreseeable future; (5) Collapsed or collapse imminent.

Below is a summary table of results of the CCTV survey

 

Internal Condition Grade

Number of Surveys

Total Length of Pipelines (m)

Surveyed Length of Pipelines (m)

Grade 5

4

212

212

Grade 4

192

9664

8642

Grade 3

41

1452

1062

Grade 1 or 2

144

6194

3769

Total

381

17522

13685

 

There are four pipe materials in the network. The correlation between pipe materials and internal condition is summarised below. The percentage of pipelines with an internal condition grade of 4 or 5 is shown for each material.

 

Material

Number of Surveys

Total Length of Pipelines (m)

% of Pipes with ICG 4 or 5

Asbestos Cement

149

7290

54%

Concrete

187

8169

53%

Cast Iron

38

1779

29%

Brick

7

284

57%

 

Hydraulic Modelling and Analysis

In evaluating a wastewater collection system one of the most important aspects to be considered is the hydraulic carrying capacity of the system. This determines the adequacy of each length of sewer to be able to convey present and projected future flow rates. To carry out the hydraulic analysis, current sewer data together with present and future flow rates were built into a computerised hydraulic model. The model was then used to determine the flow characteristics of the sewer, i.e. whether flowing partially full or surcharged and to relate projected wastewater flow rates to the carrying capacity of the receiving sewer and trunk lines based on their size, roughness, slope and depth of sediment.

To determine the hydraulic capacity of the wastewater collection system, an hydraulic model called Hydrowork was used. Hydrowork Model is a commercial software designed specially for the hydraulic analysis of wastewater and drainage systems. To simplify the analysis of the existing collectors and trunks and to allow the projected growth that will occur within the immediate vicinity of Baku to be incorporated more readily into the analysis. For determination of the projected wastewater flow rates the centre of the Baku City, and the portions of the districts that are discharging by gravity, and /or pumping to the Hovsan and Zykh treatment plants have been divided of spatial parameters on average wastewater flow, type of sewers and collection systems, drainage network capacity, infiltration rates, population and industrial density. The final map including surficial features, mentioned above has been spatial parameters and table digitized in order to carry out further analysis by used GIS. As shown in figure1, the eight (8) drainage sub-areas with homogeneous wastewater parameters were identified. These sub-areas selected as spatial base for application of the Hydrowork Model. The projected wastewater production for the 2000, 2005, 2010 and 2015 were provided data on average daily wastewater flows, infiltration for each sub-areas, also determined data on population projections, peaking factors, total peak wastewater flow.

In order to determine the adequacy of the existing trunk sewer system, peak flows for year 1996, i.e. the existing condition with different scenarios, were simulated. In addition, the projected peak flow rates for the future were compared to the capacity of the system. The modelled system was upgraded to eliminate all flooding and significant surcharging. The simulation and comparison of the main sewer pipelines were carried out for the following separate conditions.

1 Scenario - simulation of existing conditions. The sewered areas are partially connected to stormwater systems and discharge untreated wastewater to the Caspian Sea, the estimated wastewater flow rate used is 527 l/c/d. Widespread flooding and surcharging is predicted to occur throughout the system. Main problem areas are 8km Collector, upstream section of the Circular Collector, Collector A at upstream Karadag system, inadequacy capacity at Pumping Station #4.

2 Scenario as 1 Scenario with all silt removed. Main problem areas are as for 1 Scenario, but less severe, and more flow can reach Hovsan treatment plant.

3 Scenario where all areas are connected to the wastewater system, using the same flows and infiltration as 1 Scenario, lake pumping terminated. Main problem areas are 8rv Collector downstream Pumping Station #3, upstream section of Circular Collector, Collector A, upstream section of Gravity Collector.

4 Scenario as 3 Scenario with upgrades for 2005 year flow. Total wastewater production is 855,000 m3/day, all reaching Hovsan treatment plant. Abandon Zykh wastewater treatment plant and connected to Pumping Station#2; upgrade system as required to minimise surcharging and eliminate flooding; new collector to take area at upstream end of Circular Collect directly to Karadag Collector.

Some localised surcharging remains as follows 8km Collector downstream Pumping Station #3 and short section of Circular Collector.

Flows are projected to fall after the year 2000, because it is assumed that the per capita water consumption rates will be reduced and that the rate of infiltration will be less, due to implementation of emergency short term measures.

 

Conclusions

The study on hydraulic modelling base was a qualitative and subjective nature and provided a real alternative to the traditional methods such as map overlays. Remote sensing technique are useful in extraction of spatial data and GIS is useful in handling spatial data efficiency. The following seemed to be representative observations :

·      The sewers appear to be in a general state of decline across the catchment due to hydrogen sulphide attack. The rate of decline and degree of degradation to date however varies spatially across the catchment, due to a combination of flow levels, flow rates, flow turbidity, toxicity of the sewer itself and the location of the sewer in the catchment. The proximity and nature of any industrial discharges could also have an effect on the degree of degradation of the sewer.

·      The degree of degradation varies from either being visible along the entire length of a survey, or, where attack is less advanced, deterioration is only visible at the more vulnerable areas, such as joints. In some cases holes, and broken and displaced joints are visible.

·      Flows within the catchment appear to of a fairly high level with velocities and often turbulent in nature. Such conditions will tend to exacerbate and accelerate any deterioration within the sewer. This is particular problem where retention times are long enough to enable the sewage to turn septic.

Acknowledgements

The authors wish to acknowledge the technical support and advice given by Mr. R. E. Dyce, Dr. A. V. Gray, Dr. F. Guliyev, Mr. E. Yusifov during this study period.

 

References

1. Chambers P., Walker S., Jefferson C. (1997) Impacts of municipal wastewater effluents on Canadian waters: a review. Water Qual. Res. J. Canada. 32:659-713.

2. ARWC. (1998). Water and wastewater Master Plan for Greater Baku. Vol.4.

3. UNDP. Azerbaijan: state of the environment report. pp:37-42.

4. Jensen K. (1998). Environmental impact assessment using the rapid impact assessment matrix (RIAM). Olsen&Olsen, VKI, Fredensborg, Denmark, pp:8-28.

5. Brown S., Engel B. (1993). Comparison of GIS assisted simulated hydrologic response with actual storm event data. In: Advances in hydro-science and engineering, Vol.1, pp:511-517.

6. Mamedzadeh I. (1998). Water situation in Azerbaijan Republic: problems, future scenarios and recommendations. In: Proc. Of International Conference on World water resources at the beginning og the 21st Century, IHP-V, Technical documents in hydrology, No.18, UNESCO, Paris, pp:465-471.