The effect of intake channel length on water temperature at the intake point of the power plant at Muara Karang power plant

. Muara Karang Power Plant (MKPP) is one of the main power plants on Java Island in Indonesia. Presently, the Jakarta provincial government has issued a reclamation project on Island G in the marine waters around MKPP. This reclamation effort is predicted to lead to a rise in the seawater temperature around the intake, which MKPP will address with the addition of intake channel of 250 - 957 m. Therefore, this study aimed to determine the effect of intake channel extension on the water temperature at the intake point using numerical modeling comprising hydrodynamics and dispersion advection modules. A total of 10 scenarios were modeled by varying intake channel length and season. The result showed that adding intake channel was less effective because the average water temperature was less than 0.24 o C with an effectiveness below 0.78%. Based on the validation of the modeling results on the measurement data, the NRMSD values in west and east seasons were 9.13% and 12.63%, respectively. Under existing conditions, the average and maximum seawater temperatures were 31.40 o C and 32.08 o C. Meanwhile, by extending intake channel, the average and maximum water temperatures were 31.16 o C and 31.60 o C. These results showed that by extending intake channel, the temperature at the intake point was generally lower than the existing conditions. Intake channel length was more effective in reducing the temperature at the intake point during west monsoon than east monsoon. Vertically, the temperature at the bottom was relatively colder than near the surface. In west monsoon, the average temperature difference between the bottom and the surface ranged from 0.16-0.21 o C, while in east, it was between 0.23 and 0.50 o C. In conclusion, the addition of subsequent structures to increase effectiveness was necessary, specifically to hold hot water in east monsoon.


Introduction
The operation of the condenser system in the Steam Power Plant (SPP) and Gas & Steam Power Plant (GSPP) depend on a considerable amount of cooling water.On average, a coal-based power plant with cooling towers requires approximately 5 to 7 cubic meters (m 3 ) of water per megawatt-hour (MWh) (Tasnim, 2020).Seawater at ambient temperature is pumped directly into the condenser through the inlet pipe, an important equipment in the turbine-boiler thermodynamic cycle of power plants.As a result, it exits the condenser at an increased temperature through the outfall.
The efficiency of the SPP or GSPP system is related to the quantity and temperature of the available cooling water (Wibowo & Asvaliantina, 2018;Genbach et al., 2021).It is important to stress that for every 1 o C increase in cooling water temperature, the efficiency of power plant system decreases by approximately 0.168% (Darmawan & Yuwono, 2019).Therefore, most SPP or GSPP facilities are strategically built in coastal areas with unlimited water sources.
Power generation activities tend to discharge wastewater back into the sea through cooling canals to reduce its temperature.However, after passing through these cooling channels, the water remains warmer than the surrounding sea.This temperature differential is mainly governed by the following physical processes: advection and diffusion (Cahyana, 2011;Panigrahi & Tripathy, 2011;Mirza et al., 2021).The distribution of heat in the cooling canal is influenced by several factors, such as the volume and discharge rate of wastewater, initial wastewater temperature, bathymetry conditions, ambient seawater temperature, and the circulation patterns of ocean currents near the location of wastewater discharge into seawater bodies (Cahyana, 2011;Panigrahi & Tripathy, 2011;Fikri et al., 2020).
Hot water discharged from power plants into natural water bodies was identified as a source of heat or thermal pollution (Harmon, 2021).Heat pollution is defined as any deviation or increase from the natural ambient temperature in an ecosystem, which could be due to high temperatures associated with industrial cooling activities or the release of warm water into rivers enclosed by large embankments (Dodds & Whiles, 2010;Geurdes, 2023).The discharge of hot water from cooling canals into seawater bodies can potentially disrupt the sustainability of coastal and marine ecosystems.Meanwhile, detrimental effects were observed when an increase in the ambient sea temperature exceeded the threshold for the survival of marine biota (Rosen et al., 2015;Aljohani et al., 2022).Dallas (2009) stated that all organisms had a certain temperature range for optimal growth, reproduction, and fitness, often called the optimum thermal regime.The high temperatures from power plant thermal discharges severely affect the benthic fauna living near the discharge outlets (Deabes, 2020).An increase in temperature was observed to induce stress or mortality in organisms (Geurdes, 2023).
Hot water discharge not only affects the ecosystem but also influences the performance of electricity generators.This problem occurs when the hot water discharge reaches the location of power plant intake point.Generally, the water from the cooling system is hotter than the surrounding one, with temperatures reaching approximately 40°C (Yustiani et al., 2015;Fikri et al., 2020).At the same time, the temperature of the surrounding waters is relatively 30 o C.These power plants usually require 45 to 55 m 3 /s of water to cool every megawatt at full load (Fudlailah et al., 2015).The efficiency of power plant is highly dependent on the ambient water temperature.According to Petrakopoulou et al. (2020), every 10 o C increase in ambient water temperature decreases the efficiency by 0.3 to 0.7%.Makky and Kalash (2015) stated that an increase in temperature of 1 o C of cooling water from the environment decreased the power plant output and thermal efficiency by 0.45% and 0.12%, respectively.Therefore, cooling recirculation technology is important to reduce heat pollution and enhance power plant reliability (Miara et al., 2018).
Muara Karang Power Plant (MKPP) is a steam and gas power plant situated on the north coast of Jakarta City, playing a significant role in the power generation infrastructure of Java Island.It is an integral part of the Jakarta Bay Ecosystem in the Java Sea, Indonesia, as shown in Fig 1 .MKPP is crucial in supplying electricity to Java Island, particularly in Jakarta, the capital city.The peak load demand for the Jakarta metropolitan area in 2015 reached approximately 7293 MW (BTIPDP-PTRIM, 2016).
The operational activities of MKPP require discharge rates of + 180,500 m 3 /hour of water through two intakes and outfalls (PJB UP Muara Karang, 2020).Presently, the Jakarta Provincial Government is undertaking a reclamation project near MKPP on G Island.This reclamation is expected to increase the seawater temperature around the intake point, leading to disturbances in the natural water circulation and a degree of isolation from the open sea (BTIPDP-PTRIM, 2016).Furthermore, the effects of climate change result in a yearly increase in ambient temperatures.This rise significantly impacts gas turbine performance, mainly due to the high temperatures at the compressor inlet (Fatimah et al., 2019).
To address the issue of hot wastewater affecting the temperature of the intake point, MKPP plans to extend intake channel by 957 m, placing its end approximately 2 kg from the beach.However, this extension project requires a significant cost.In order to evaluate the impact and effectiveness of the channel extension on the intake point temperature, it is necessary to study the computational modeling of effluent dispersion patterns from the steam power plant.In 2019, MKKP implemented several steps to improve its wastewater treatment plant, resulting in a 21% reduction in service water usage compared to the monthly average (Hutajulu et al., 2020).
Modeling technology has been widely used as an effective approach to optimizing designs according to the conditions of an area (Aljohani et al., 2022).In the last few years, several numerical models, particularly those using Delft3D-FLOW, have been developed to investigate thermal pollution caused by power plant discharges (Laguna-Zarate et al., 2021).Typical examples include the application of numerical modeling with Delft3D-FLOW to simulate thermal plumes originating from the Veracruz Power Plant in the Gulf of Mexico (Durán-Colmenares et al., 2016), and the Yanbu-Saudi Arabia Power Plant (Aljohani et al., 2022).Numerical modeling of water thermal dispersion using MIKE has been carried out in different locations, including the Paiton Power Plant (Fudlailah et al., 2015;Fikri et al., 2020), Lekki Coast-Nigeria (Panigrahi & Tripathy, 2011), Bandar Abbas Power Plant-Iran (Abbaspour et al., 2006), and PT Kilang Pertamina International Kasim process plant in Sele Strait, West Papua (Yesaya et al., 2023).Additionally, the numerical simulation of water temperature in the R´ıo de la Plata River and Montevideo's Bay was conducted using the finite element numerical model RMA-10 in its 2D vertical integrated mode (Fossati et al., 2011).
Several studies have been conducted on thermal dispersion, although none has examined or modeled the effect of extending intake channel.It is important to note that the heat distribution emanating from MKPP has the potential to extend over an area with a large size of 156 hectares (Mihardja et al., 1999).The numerical modeling results showed that the temperature around MKPP intake channel decreased by 1 to 3°C due to the reclamation master plan (Islami et al., 2020).The reclamation of G Island is expected to raise the average temperature at the intake location by 0.32 to 0.7 o C (Khoirunnisa et al., 2021).Furthermore, Suntoyo et al. (2021) conducted an experimental study on the hydraulics of the water intake channel (Suntoyo et al., 2021).The study conducted by Hananta (2018) focused on the impact of the reclamation of Island G using hot water dispersion.However, this study did not address the plan to extend intake channel.Presently, no investigation has been conducted on the effect of intake channel length on the cooling water temperature in power plant.Therefore, the current study was conducted to determine the effectiveness of extending MKPP intake channel.The results are expected to provide crucial insights for future strategies addressing this issue.

Materials and Methods
This study explored various intake channel length scenarios in a specific domain.The model simulation was performed using MIKE 3, a software package developed by the Danish Hydraulics Institute (DHI), which included hydrodynamic and dispersion advection modules.MIKE 3 is a widely recognized and reliable tool for consistently delivering highly accurate results across various applications.The modeling effort also included calculations near the emission source, using the Coupled to MIKE 3 Solution module.However, the verified results of hydrodynamic and thermal dispersion modeling using MIKE21 showed a similar pattern compared to field measurements (Abbaspour et al., 2006;Fikri et al., 2020).The results of the study conducted on the exhaust cooling system of LNG facilities in Kutch Bay, India, showed that the correlation coefficient between the modeling predictions and actual measurements was in the range of 86 and 98% (Gupta et al., 2014).

Governing equation
The modeling process in this study applied a hybrid equation system combining the hydrodynamic model, which is associated with current dynamics, and the thermal dispersion model.The hydrodynamic model incorporated the continuity (Equation 1) and momentum formula with depth smoothing, as stated in Equations 2 and 3.Meanwhile, the thermal dispersion model used the dispersion advection equation (Equation 4) (Danish Hydraulic Insitute, 2017).The numerical method applied in this model was the finite difference method.

Equation of continuity:
Equation of momentum in the x-direction: Equation of momentum in the y-direction: Where h(x,y,t) is the depth of water (=-d, m),  (x,y,t) is the variation of water depth in time (m), (x,y,t) is the surface elevation (m), p,q (x,y,t) is flux density in x and y (m 3 /s/m), u & v is the velocity at average depth in x and y, C(x,y) is the resistance of Chezy (m 1/2 /s), g is the acceleration due to gravity Governing equation for advection and dispersion:  ), S is Qs, (cs-c), Qs is source/sink discharge (m 3 /s/m 2 ), and cs is component concentration in the source/sink discharge.

Study Stages
The sequence of stages in this study commenced by modeling ten distinct scenarios.Subsequently, the domain model was defined and built while considering both area and time.The preparation of input data for the setup and execution of the models followed this.The modeling results were validated through a comparison with field data.The final stage requires post-processing the modeling results for further analysis and presentation.

Input data
The advection-dispersion thermal modeling depended on the main input data shown in Table 1.However, the climate in Jakarta showed seasonal variations, with temperatures ranging from 25 to 31°C and 25 to 33°C during west and east seasons.In October, seawater temperature typically falls from 27 to 31°C.Humidity in Jakarta varies between 61% and 95%, and the average monthly rainfall amounts to 218.4 millimeters (mm).The wet season occurs between November and April, while May through October are typically dry (World Bank Group, 2021).
The thermal dispersion modeling at the open boundary used results obtained from HD models, comprising critical factors such as surface elevation, current velocity, and direction.The HD model covered a larger domain, approximately 32 x 61 km, using the surface elevation data extracted from the Tidal Model Driver (TMD) for 2019, available at one-hour intervals (Padman & Erofeeva, 2005).The values associated with the location of outfall, and intake discharges from PLTU Muara Karang are 14.4 m 3 /s -30.4 m 3 /s, and 15.08 m 3 /s -35.07 m 3 /s, respectively (PJB UP Muara Karang, 2020).
The wastewater temperatures at outfall 1 of MKPP during west and east monsoon were recorded at 35.5 o C and 35.2 o C, respectively.Meanwhile, at outfall 2, during west monsoon, the wastewater temperature was 34.7 o C, and in east, it decreased to 34.2 o C (PJB UP Muara Karang, 2020).The initial ambient  West-Existing+500 Simulation in the west season with the length intake channel is the existing intake channel plus 500 m. 4 West-Existing+750 Simulation in the west season with the length intake channel is the existing intake channel plus 750 m. 5 West-Existing+957 Simulation in the west season with the length intake channel is the existing intake channel plus 957 m. 6 East-Existing Simulation in the east monsoon with the existing intake channel length 7 East-Existing+250 Simulation in the east season with the length intake channel is the existing intake channel plus 250 m. 8 East-Existing+500 Simulation in the east season with the length intake channel is the existing intake channel plus 500 m. 9 East-Existing+750 Simulation in the east season with the length intake channel is the existing intake channel plus 750 m. 10 West-Existing+957 Simulation in the east season with the length intake channel is the existing intake channel plus 957 m. temperature was set at 30.5 o C (PJB UP Muara Karang, 2020), with a horizontal and vertical dispersion of 0.01 m 2 /s and 0.0001 m 2 /s, respectively.

Domain of model
The reclamation of Island G had been completed, except for the validation modeling domain.The overall domain size is approximately 9 x 12 km, as shown in Figure 2.This domain is divided into three nested parts, with the smallest section centered around MKPP, featuring a maximum mesh area of 1000 m 2 .The input surface elevation at the open boundary was extracted from a larger model comprising the entirety of Jakarta Bay, covering an expansive modeling domain of relatively 61 x 32 km.Specifically, MKPP is equipped with two outfalls and the intake point for disposing of hot water waste and cooling it, respectively, all located in close proximity, as shown in Fig 2.
This study used ten scenarios, defined by intake channel length and season, as shown in Table 2.The simulation period accounts for both west (January 2019) and east monsoons (July 2019).

Validation of Modeling Results
In this study, validation is a crucial step focused on assessing the performance of the hydrodynamic model, particularly the surface elevation conditions.This process relies on a detailed comparison of the modeling results with the measurement data obtained from the Kolinamil station, located at coordinates 106.89083 o E and -6.For the current velocity, due to the absence of direct measurement data, the validation process for this parameter was carried out qualitatively, drawing on the results from previous studies.Based on the existing map of Jakarta Bay, it was estimated that the current velocity in both the bay and near the coast was relatively 0.05 m/s (BAPPEDA Provinsi DKI Jakarta,

2015)
. In general, the hydrodynamic conditions in Jakarta Bay are characterized by significant variability in the direction of the ocean's current, with an average current velocity of approximately 0.02 m (Pranowo et al., 2014).A similar study stated that the current velocity at Kayangan Station Teluk Jakarta ranges from 0.002 to 0.05, with prevailing directions predominantly to west and east (Surya et al., 2019).Based on the modeling results obtained in May 2019, the current speed ranged from 0.001 to 0.045 m/s, with dominant directions being west and east, as shown in Fig 4 .The thermal dispersion modeling results were validated in January and July for west and east seasons, respectively.Temperature measurements to validate the modeling results were performed at eight specific points by MKPP, as shown in Fig 5a (PJB UP Muara Karang, 2020).A visual representation of the temperature comparison between the measurement and modeling results at these eight points is shown in Figs 5b and c.This validation showed that the NRMSD values in west and east seasons were 9.13% and 12.63%, respectively.Validation can be performed using remote sensing techniques, assuming the image data is accessible.This result is similar to the approaches applied at the Gujarat Power Plant (Roy et al., 2022).

Temperature Variation at The Water Intake Point
The temperature of thermal wastewater affects seawater at the intake point during east and west monsoons.However, the longer intake channel, the lower the seawater temperature at the intake point (Shawky et al., 2015).Under existing conditions during west monsoon, the average and maximum seawater temperatures at the intake point are 31.40o C and 32.08 o C, respectively.However, when intake channels were extended, there was a significant reduction in the average and maximum water temperatures at the intake point, which dropped to 31.16°C and 31.60°C, as shown in Table 3.The same phenomenon occurred in east monsoon, although the maximum seawater temperature at the intake point was higher, except in the Existing+957m scenario.
The seawater temperature at the intake point is slightly higher in east monsoon compared to west season.This variation is mainly attributed to the thermal wastewater from outfall 2, which flows through the Mutiara Beach canal, carried by prevailing currents and eastward winds, although partially obstructed by G Islands.Consequently, this phenomenon raises the temperature at intake channel mouth, and point.During west season, the presence of G Island slightly obstructs the flow of wind and currents from west, limiting the transfer of heat from outfall 1 toward the intake channel.
Tides significantly influence the distribution pattern of hot discharge water from power plants (Mihardja et al., 1999;Fossati et al., 2011;Rosen et al., 2015;Wibowo & Asvaliantina, 2018).In west monsoon, the seawater temperature at the intake point is highest at low tide, as shown in Fig 6a .Meanwhile, in east monsoon, the highest mean temperature at the intake point coincides with the lowest tide, as shown in Fig 6b .This observation is associated with the lowest tide, during which wastewater from outfalls 1 and 2 is directed towards intake channel mouth, eventually reaching the intake point.
In west monsoon, all scenarios concerning the extension of intake channel tend to reduce the seawater temperature at the intake point.The magnitude of this temperature decrease becomes more pronounced with longer intake channels, as shown in Table 3. Specifically, during west monsoon, the Existing+957 m scenario was unique, resulting in a decrease in the average water temperature at the intake point from 31.40°C to 31.16°C, marking a 0.77% reduction.During west monsoon, Existing+957 m scenario decreased the average water temperature at the intake point from 31.40 to 31.16 o C, marking a 0.77% reduction.The maximum temperature also declines, from 32.08°C to 31.60°C, representing a 1.50% decrease.This phenomenon is predictable because the longer intake channel positions its mouth farther away from the hot water waste disposal outlet.As a result, the water entering the intake point is cooler, which explains the observed temperature reduction.
During east monsoon, the extension of intake channel scenarios does not generally reduce seawater temperature at the intake point.Meanwhile, only in the Existing+957m scenario can the average and maximum temperatures decrease at the intake point.This was mainly influenced by the thermal wastewater from outfall 2, which, under normal circumstances, moved from east to west but encountered obstruction from G Islands.The temperature at intake channel mouth at the intake is affected.Therefore, by comparing all scenarios other than Existing+957 m, the maximum temperature remained higher, as shown in Table 3.In east monsoon, Existing+957 m scenario only yielded a slight reduction in the average water temperature at the intake point from 31.72 to 31.51 o C (0.65%).At the same time, the maximum decreased from 32.16 to 32.02 o C, a 0.45% reduction.
Hao et al. also studied at the Huadian Ministry of Power Plant to explore the impact of heated water retaining designs.The study showed that the walls and barriers reduced the maximum temperature at the intake point by 1.0 to 1.3 o C, with an average decrease of 0.2 o C. Another study showed that constructing a hot water retaining structure could reduce seawater temperature at power plant intake by 1.12 to 1.24% (Hao et al., 2020).The results suggested that adding intake channel in the 250 to 957m range was less effective compared to other heat-retaining structural designs.This present study reported that the average water temperature at the intake point decreased only by 0.01 to 0.24°C, corresponding to a 0.02 to 0.78% reduction.
The temperature reduction at the intake point is highly dependent on various factors, including the design and length of the heat-retaining structure, distance from the outfall, and bathymetry (Shawky et al., 2015).Meanwhile, the extension of intake channel is more effective in reducing the temperature at the intake point during west monsoon compared to east.In east monsoon, the flow of hot water, which generally dispersed to west, was blocked by G Island, and resulted to higher temperatures at intake channel mouth than at the intake point.When intake channel length is limited to 250 m, 500 m, or 750 m, the effectiveness is reduced, thereby leading to an increase in temperature at the intake point.
The water temperature specification at the condenser inlet differs between Steam Turbine Generators (STG 1, 2, and 3) at 30.4 o C and Steam Power Stations 4 and 5 at 32 o C (PJB UP Muara Karang, 2020).Therefore, the cooling water input for the Steam Power Station met the existing specifications in all scenarios.Pre-treatment is needed for the cooling water input at the Steam Turbine Generators to meet the specified requirements.One method often used is a cost-effective cooling pool that has a simple design but requires a large land area.By adopting this method, the discharge water temperature from the outfall was regulated to remain in 4°C of the ambient temperature, incurring an estimated cost of approximately Rp. 806 billion (Nurdini, 2017).Complying with the seawater quality standard, which demands a maximum temperature difference of 2°C from the ambient seawater temperature, requires substantial financial commitment.
The estimated cost for constructing an average dike height of 4 m in the sea and 957 m extension of intake channel at MKPP was approximately Rp. 60.29 billion, with each meter costing approximately Rp. 63 million (Suranto et al., 2021).In a comparative context, the Bandar Abbas Thermal Power Plant in Iran built a 500 m long outlet channel in 2005 at an approximate cost of 634,147.8USD (Abbaspour et al., 2006).
In the seawater surrounding MKPP, the macrobenthic diversity index is quite high, relatively 1.19, while evenness is 0.49 (Wulandari et al., 2021).Among the macrobenthic organisms, the Polychaeta and Mollusca groups are the dominant species.Water temperature greatly influences aquatic life, but because the temperature change is less than 0.5 o C, it does not have numerous impact on benthic organisms (Deabes, 2020).
The abundance of phytoplankton in the waters around MKPP ranges from 70 to 620 ind/l (Islami, 2018).While the temperature tolerance limit for plankton was recorded at 35°C  (Nybakken, 1992), other aquatic organisms, namely Fish 38.1 o C, Crustacea 37.9 o C and Mollusca 36.7 o C, also showed varying tolerance limits (Mihardja et al., 1999).It was reported that phytoplankton tend to be relatively unaffected by temperature fluctuations.
During both west and east monsoons, there is a vertical temperature difference in the water, with the bottom being slightly cooler than the surface, as shown in Fig 7 (Hasita et al., 2013;Aji et al., 2017).This temperature variation is mainly due to the influence of sunlight, which heats the water's surface.In west monsoon, the average temperature difference between the bottom and the surface falls in the range of 0.16 to 0. The extension of intake channel had a more pronounced effect during east monsoon, mainly because the surface temperature of the intake point was increased due to the heat from the hot water discharge.

Temperature variation along the intake channel
The temperature conditions along the intake line for the five scenarios at the end of the simulation are shown in Fig 8 .During west monsoon, there is a typical pattern where the water temperature tends to be higher as it moves closer to intake channel mouth, with the exception of the existing conditions.The pattern is mainly influenced by the length of the channels; shorter ones, which are closer to outfall 1 on west, showed lower temperatures at the mouth.This is because the wastewater discharge contributed heat to intake channel mouth.The temperature at the intake point is consistently lower than the existing conditions, except for the Existing+250 m scenario.The intake point experienced higher temperatures, showing heat transfer.This deviation from the norm is due to the limited cooling effect from the surrounding air.
In east monsoon, there is a prevailing pattern where the water temperature generally rises as it approaches intake channel mouth, except in the cases of the existing conditions and Existing+250 m scenario.This increase in temperature is associated with the intake channel length.Furthermore, the longer intake channels, the higher the temperature at the mouth.This phenomenon was majorly attributed to the movement of hot wastewater from outfall 2, which flowed through the Mutiara Beach canal.The wind and currents carry this heat from east to west, increasing temperatures at the mouths of Existing+750 m & Existing+957 m intake channels.
The temperature at the intake point remains relatively stable, similar to the existing condition, except in the cases of Existing+750 m and Existing+957 m scenarios.It showed that in Existing+250 m and Existing+500 m scenarios, the heat was still transferred to the intake point, as there had been a significant cooling effect from the surrounding air.
The snapshot modeling results when the temperature at the intake point was at its highest are shown in Figure 9.It shows the heat distribution pattern of MKPP outfall 1 and 2 wastewaters in west and east seasons.The red and blue colors in this representation show the highest and lowest temperatures, respectively.During west season, the predominant water flow is eastward, resulting in the major source of heat affecting intake channel being the wastewater discharge from outfall 1, located to west of intake channel.Meanwhile, the heat from outfall 2, situated to east of intake channel, does not significantly affect the channel during west monsoon, as shown in Figure 9.In these scenarios, intake channel length becomes a crucial factor.Longer intake In east season, the dominant flow direction is westward, leading to a significant influence on the water temperature at intake channel mouth by the hot wastewater originating from outfall 2, which flows through the Mutiara Beach canal.Meanwhile, the heat generated by wastewater from outfall 1, located west of the channel, has no discernible impact as it disperses westward, away from intake channel.In this particular situation, intake channel length is a critical factor.Longer intake channel shows higher water temperatures at the mouth because it is positioned closer to the end of the Mutiara Beach canal, where wastewater from outfall 2 flows.Therefore, it is essential to implement control measures or other modifications to prevent heat from wastewater, specifically during east season.

Conclusion
Intake channel length is more effective in reducing the temperature at the intake point during west monsoon than east.During west and east monsoons, the average temperature differences between the bottoms and the surfaces ranged from 0.16 to 0.21°C and 0.23 to 0.50°C, respectively.As a general trend, water temperature increased as it approached intake channel mouth.However, the incorporation of intake channel measuring 250 to 957 m was not considered optimal in the past because it resulted in only a marginal reduction in the average water temperature at the intake, ranging from 0.01 to 0.24°C, with an effectiveness of 0.02 and 0.78%.To effectively address this issue, the addition of another heat-retaining structure, such as a north-south dike positioned on east side of intake channel mouth, was essential.This measure was crucial for reducing the impact of wastewater from outfall 2, specifically during east monsoon.

Fig 1
Fig 1 Location and Area of Study Thermal at MKPP the concentration of component (unit arbitrary), u & v is the horizontal velocity in x and y (m/s), w is vertical velocity

Fig 2
Fig 2 Domain Thermal Dispersion Modeling at MKPP

Notes:
The modeling domain assumes that Island G's reclamation has been completed except for the modeling domain for validation | 136 ISSN: 2252-4940/© 2024.The Author(s).Published by CBIORE 10667 o S. The validation result is expressed through the NRMSD (Normalized Root Mean Square Deviation) value, which is measured at 1.354%.It means that the results of the model are in line with the field measurements, with an accuracy exceeding 98%.Fig 3 provide a visual representation of this consistency.A comparison of the modeled surface elevation and the measurement results is shown in Fig 3.

Fig 3
Fig 3 Comparison of Surface Elevation between Modeling Result and Measurement

Fig 5 Fig 6
Fig 5 Validation of Thermal Dispersion Modeling Results on Measurement Data (a) Location of Temperature Observation, (b) Temperatur Comparison Model Vs.Measurement in West Monsoon, (c) Temperatur Comparison Model Vs.Measurement in East Monsoon

Fig 7
Fig 7 Temperature Comparison at The Surface and Bottom Layer at Cooling Water Intake Point (a) West Monsoon (b) East Monsoon 21 o C, as shown in Fig 7a.Meanwhile, this difference is larger in east monsoon, ranging from 0.23 to 0.50 o C, as shown in Fig 7b.

Fig 8
Fig 8 Surface Temperature along Cooling Water Intake Channel (a) West Monsoon (b) East Monsoon

Fig 9
Fig 9 Snapshot Modeling Results when The Temperature at the Intake Point is Maximum

Table 2
Scenarios of thermal dispersion modeling at MKPP

Table 3
The average and maximum temperature at the water intake point when west monsoon and east monsoon ISSN: 2252-4940/© 2024.The Author(s).Published by CBIORE