STUDYING OF HEATED WATER RELEASED FROM SOUTH-BAGHDAD ELECTRIC POWER STATION TO THE TIGRIS RIVER

Thermal pollution occurs when heated wastewater is discharged into rivers, lakes, oceans, or other water bodies. This will raise the temperature of the water body above its normal level and, consequently, will harm the aquatic live. Thermal Pollution problems will intensify as electricity usage increases unless substantial changes are made in the mode of discharge of the heated water. This paper is aimed to study the effects of heated water released from South-Baghdad Power Station on the water quality of Tigris River. Many parameters are test such as: Temperature (T), Total suspended solids (TSS), Total Dissolved Solids (TDS), Electrical Conductivity (EC), Hydrogen Ion (pH) and the dissolved oxygen (DO). Other parameters are tested to describe the heated water components such as Biochemical Oxygen Demand (BOD), Oil+Grease

Thermal pollution problems will intensify as electricity usage increases unless substantial changes are made in the mode of discharge of the heated condenser cooling water.Steam generation of electrical power plant requires rejection of tremendous quantities of waste heat typically 58% -67% of the energy input to the plant from the generation units to the surrounding (Paily et al., 1974).This heat is transferred in the condensers from the low-pressure steam to the cooling water, and then directly to the atmosphere by the means of a cooling tower, or directly discharge to the water body(Fig.1).
The directly discharge of heated water to the river can be more dangerous to the health of the receiving water than organic pollution.Higher temperature reduces solubility of oxygen and chemical reactions proceed at a faster pace (Masters,1998).
Al-Jalaby (1994) developed a two-dimensional numerical model for the simulation of the spread and mixing of thermally polluted water disposed into the river flow.This model considers the effect of density difference between the pollutant density and the river water density.Finite difference up winding scheme is used to solve partial differential equations, which include the momentum conservation, energy conservation and (K- ) turbulence model.The results of this model are verified by integral heat balance analysis.This model is found to be sensitive to the variation in the river velocity and density.It is also insensitive to the variations in wind speed.Bormans and Webster (1998) investigated the thermal stratification dynamics of the slowflowing rivers of the Marray-Darling Basin.The net surface heat flux and the river discharge are the two most important parameters that determine the stratification status of the rivers with little effect from direct wind mixing.Excellent agreement between measured and simulated temperature profiles under a wide range of river discharge and meteorological forcing is obtained.(1998) presented the mathematical model to predict the long-term effects of once through cooling systems on local fish population.The fish life cycle model simulates different life stages of fish by using appropriate expressions represented by growth and mortality rates.The heart of the developed modeling approach is the prediction of plant caused reduction in total fish population by estimating recruitment to adult population with and without entertainment of ichthyoplakton and impingement of small fish.The model is applied to a local fish species, gilthead (Sparus aurata), for the cause of a proposed power plant in the Aegean region of Turkey.The simulation indicates that entertainment and impingement may lead to a population reduction of about 2% to 8% in the long run.Joody (2001) developed one and two dimensional numerical models for the simulation of the spread and mixing of thermally polluted water disposed into the river released from the AL-Doura Power Station starting from the outfall up to 1000m downstream.The momentum and thermal -energy equations were used to describe the distribution of velocity and temperature in river.The two dimensional model also incorporates with the (k- ) model to calculate the distribution of turbulent viscosity.The two dimensional model also discusses two cases; the first case neglects the effect of vertical velocity distribution, while the second case include it.Comparison of observed data on Feb, 3,2001 andJuly, 27,2001 with data computed by two-dimensional model shows good agreement with error of 0.57% and 1.95% respectively.

Cakiroglu and Yurteri
Al-Suhaili and Jasim (2006) applied two dimensional numerical model for estimating temperature distribution in a river.This model was found to be sensitive to the wind speed.A laboratory physical model was built to find experimental data.The comparison of the observed results from Al-Doura Power Station and laboratory physical model with those computed by the numerical model showed a good agreement and the maximum absolute difference percentage were 16.2 %, 8.6 % respectively.

Measurements and Field Work
A river reach of 500 m Long was involved in the present work.It is started from the outfall structure of South-Baghdad station and extended to 500 m downstream.Samples were collected to predict the essential variation of the water quality after the heated water discharge.
The cooling system applied in South-Baghdad power station is once through cooling system in which the cooling water is withdrawn from the river via two pipes (1.4 m diameter), and then it is conveyed to underground rectangular channels that convey the cooling water to the six condensers with water temperature increase to about 10-15 °C.The heated water returns to the river via an underground discharge channel and an outfall structure located in the shoreline downstream on the intake structure.
Different field measurements were performed and different data were gathered, which can be mainly classified as stream, wastewater and raw water sampling.
Stream sampling is considered to represent and give reliable measurements of water quality constituents along the stream reach.Seven parameters are involved in the present work.These parameters are temperature (T), dissolved oxygen (DO), Electrical conductivity (EC), total suspended solids (TSS), total dissolved solids (TDS) and hydrogen ion (pH).
The temperature and dissolved oxygen were measured by using portable device.While, the remaining measurements were collected every week using plastic bottle of 0.5 liter capacity and sent to laboratory of the Power Station to be tested.Collection of samples was usually conducted using a boat.
Tables from 1 to 6 show the values of TSS, TDS, EC, pH, T, BOD, Oil & grease and PO 4 .While, figure from 2 to 7 show the variation of dissolved oxygen concentrations along the study reach Four parameters are involved in the present work, which are biochemical oxygen demand five day (BOD 5 ), Oil+grease, TSS, and (PO 4 ), These samples were collected once in a month (started from April and ended in July)

Results and Discussion
 The TSS concentration decreases at the outfall location in which the temperature increases.The increase of temperature will have effect on density of water (density decreases with temperature increase), therefore the suspended solids will move downward the river bottom.But in the case of washing of condensers, the concentration of TSS increases at the outfall because the washing water will be released to the river directly. The maximum TSS concentration measured at outfall location on 3/1/2002 and its equal 188-ppm, this high value may be attributed to the high concentration of TSS released from the condensers of power plant at that time, while the minimum TSS concentration measured at outfall location on 18/6/2002 and 15/7/2002 which is equal 8 ppm.
 TDS and EC concentrations increase at the outfall location due to increase in the dynamic energy of molecules, this leads to an increase in the dissolution salts in turn in (TDS) and (EC), For example the concentrations of TDS and EC on 21/3/2002 are 677 ppm and 989 micromhos/cm at outfall location, while they equal 610 ppm and 969 micromhos/cm at 50 m far from outfall location in which the temperature of water river decreases. Maximum concentration of TDS measured at outfall location on 3/1/2002, which is equal 895 ppm while the minimum concentration of TDS measured upstream on 4/6/2002,which is equal 345 ppm.
On the other hand, the maximum concentration of EC measured at outfall location on 16/1/2002, which is equal 1220 micromhos/cm.whilethe minimum concentration measured at 100 m far from outfall location on 2/7/2002, which is 605 micromhos/cm.Moreover the concentration of EC some times exceeds the allowable limits (1000 micromhos/cm). The test of stream water at the study reach shows there is no effective change in pH concentration mainly at the outfall location; this can be attributed to the logarithmic equation of pH.Field observation shows, those concentration levels of pH are acceptable along the study reach and still with allowable limits of Iraqi Standards (from 7 to 8.5). The concentration of Dissolved Oxygen (DO) is often used as index for water quality.At least 4 (mg/l) are required to maintain a balance of desirable species in the water.On the other hand, field observation shows that the concentration of dissolved oxygen is acceptable along the study reach, i.e greater than allowable limit of Iraqi Standards (more than 5 mg/l), but there is sudden dropping at the outfall location because of temperature increasing. The test of heated water released to the Tigris River shows that there are illegal concentrations of BOD 5 and Oil.The high concentration of Oil (above 10 mg/l according to the Iraqi standards, see tables 5 and 6

CONCLUSIONS
 The dissolved oxygen of water river does not drop under the allowable limits (5 mg/l according to the Iraqi standards) so that there is no sever effect on the organisms lived in the river. The concentrations of total dissolved solids are within the allowable limits (1000 mg/l according to the Iraqi Standards) along the study reach. The Electrical Conductivity exceeds the allowable limits (1000 micromhos/cm) along the study reach in some tests during the study period. The pH concentration is not affected by increase in temperature in study reach. The heated water samples showed that the concentration of BOD 5 are slightly rising comaired with the samples taken from the raw water.
-Ren and Righetto (1998) presented unsteady state two-dimensional model to simulate the velocity and temperature fields in the estuary of the Yangtza River in Brazil.The computation is based on the advanced turbulence depth averaged two equations (k-) model.Variations of bottom topography and water surface elevation are included.The distribution of velocity and temperature computed by turbulence model (k-) is compared with experimental results and field data.It is found that the simulation by using (k-) model can provide more details of flow fields and temperature distribution than once by using phenomenological algebraic for models of eddy viscosity and diffusivity.
) comes from the State Company for Vegetable Oils which disposes high concentration of oil upstream the South-Baghdad Power Station.Also the power plant itself disposes oil to the pipe of heated water.BOD 5 test shows there is illegal concentration in June and July (above 40 mg/l according to the Iraqi standards) because the difference in inlet and outlet water temperature.Also the State Company for Vegetable Oils disposes high concentrations of BOD 5 and TSS up stream Power Station at that time.PO 4 concentrations are within the permission value of Iraqi standard which is (3 ppm).