ASSESSING THE CAPACITY OF RECEIVING WASTEWATER OF RIVER FOR DECISION SUPPORT ON WATER RESOURCES PROTECTION CASE STUDY: THUONG RIVER

ASSESSING THE CAPACITY OF RECEIVING WASTEWATER OF RIVER FOR DECISION SUPPORT ON WATER RESOURCES PROTECTION  CASE STUDY: THUONG RIVER

ASSESSING THE CAPACITY OF RECEIVING WASTEWATER OF RIVER FOR DECISION SUPPORT ON WATER RESOURCES PROTECTION CASE STUDY: THUONG RIVER

17:23 - 16/03/2018

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Water quality simulation of the Thuong river for years of  2020 and 2030 showed that the water has signs of contamination. The pollution levels are different along the river. The most polluted locations are at Bac Giang city and Yen Dung district, due to Hoang Van Thu paper  factory, Ha Bac fertilizer plant and some other facilities. The main  contaminated parameters are PO4 and NH4 with concentrations reac

ASSESSING THE CAPACITY OF RECEIVING WASTEWATER OF RIVER FOR DECISION SUPPORT ON WATER RESOURCES PROTECTION

CASE STUDY: THUONG RIVER

Trinh Thi Thu Vana, Bui Cong Quangb

a Department of Water Resources Management, Ministry of Natural Resources and Environment, Hanoi 10000, Vietnam

bProfessor. Dr, Water Resources University, Hanoi 10000, Vietnam

 

 

Abstract

Thuong river, a tributary of the Red River basin, is currently facing the degradation in both water quality and quantity. One of the major causes of water pollution is wastewater discharge into rivers and streams from industrial plants, agriculture and residential that untreated or treated but does not  meet the national standards. In many river stretches, especially in  Bac Giang city and industrial areas,  wastewater load  to Thuong river exceeds its self-purification capacity, and it may cause serious damages to the water environment, aquatic life and human health. In this regards, assessing capacity of receiving wastewater of Thuong river is the important task for water quality protection and management.

In this article, model MIKE 11, a professional engineering software package for the simulation of flow and water quality model (DHI, 2003) is  used to simulate hydrodynamic, advection - dispersion and ecolab to describe the process of wastewater advection and predict water quality of Thuong river in 2020 and 2030. The model simulated 7 water quality parameters with 3 different parameters . The water quality assessment is based  on  the comparision between simulated water quality and permitted limit of Vietnamese National technical regulation on surface water quality (2015). The results show  that the water of  Thuong river is being contaminated  by industrial and residential wastewater.

Key words: capacity of receiving wastewater, water quality assessment, Mike 11 model, Thuong river in Bac Giang province

 


  1. INTRODUCTION

Thuong river has more than 440 works extracting surface water to serve the industrial production, agriculture, fisheries, living, medical and other service activities; and a total of 946 facilities discharge wastewater into river (Report on the status of water exploitation and discharge wastewater in Bac Giang province, 2012).

As the plan from 2006 to 2020, many industrial clusters and parks are to be  built in Bac Giang province, that  lead to increasing water demands and wastewater discharge to the environment. Many studies showed that the nutrients and organic pollution in Thuong river are significant (Center for Environmental Monitoring, VEA). The results of water quality analysis of Thuong river (2009 - 2013) showed that the concentration of BOD5 was higher than acceptable standard 1,86 - 3,6 times; COD was higher 1,4 - 2,73 times ; NO3 was higher 1,175 - 8,03 times and DO was lower 5,3 times in comparison with the standard (National technical regulation on surface water quality, 2015).

It can be seen that, the issue of river pollution is causing a sensation in the public opinion and poses an urgent task  to  the environmental and water resources management authorities and scientists : finding a solution to control and manage wastewater discharge operation into Thuong river to protect this water source.

The Law on Water resources (2012) of Vietnam regulates  some new provisions on water resources management and protection, especially the field of wastewater discharge management. The Article 37 of the Law states: “The organizations and individuals who discharge waste water into water sources must have a permit issued by the competent State agencies (except the small scale and waste water without a harmful chemical or radiative matter). One of the basis to grant a permit  is capacity of receiving wastewater (Decree No. 201/2013/ND-CP, 2013).

Capacity of receiving wastewater of river is the loading capacity to receive a number of pollutant while still maintains the concentration of pollutants in the water sources which does not exceed the allowable values specified in the national  water quality standards  (Circular 09/2009/TT-BTNMT, MoNRE Vietnam, 2009). The assessment of capacity of receiving wastewater requires not only to have a good long - term investigation of hydrology, hydraulic and wastewater discharge activities, but also  to assess and predict water quality in the future. Therefore, a technical approach should be applied . Mike 11 model - an unsteady hydraulic model has provides engineers with highly accurate hydraulic and water quality modelling tool  , is  selected. The primary feature of Mike 11 modelling system is the integrated structure with a variety of add – on modules each simulating phenonmenon related to river systems (DHI, 2003). To solve the problem of this study, apply three following modules: Hydrodynamic (HD), Advection - Dispersion (AD) and Ecolab. The application of Mike 11 model in the assessment of water quality has been well received among a large number of researches (A.H.Kamel et al., 2008; B.Razdar et al., 2011; Thai. H. Tran et al., 2003 and 2009).

  1. CASE STUDY

Thuong River (also known as Nhat Duc River), located in the territory of Lang Son, Bac Giang and Hai Duong province. It originates from the Na Pa Phuoc mountain (belongs to Lang Son province), and then flows into Bac Giang province (through Lang Giang, Yen The, Tan Yen, Yen Dung district and Bac Giang City). The last point is in Pha Lai town of Hai Duong province and enters Luc Nam and Cau river to form Thai Binh river.  It has 157 km length, the basin area of 6,640 km2.

The selected study area is Thuong river located in Bac Giang province (Figure 1). The total population in Bac Giang province is 1.641.231 people, in which the urban population is 136.021 (18%) and rural area is 614.312 (82%) (Statistical Yearbook 2015 of Bac Giang province). The growth rate of gross domestic product (GRDP) in 2015 was estimated 9.6%.

Topography of this area is mountainous and midland intersperses plain. Climate is tropical monsoon. In winter, the weather is cold, dry and less rainy due to the influence of the Northeast monsoon. The summer is hot, high humidity and rainy. Rainy season lasts from June to October, the dry season is from November to May. The annual average rainfall is only 1.527mm, the flow module in 15 ¸ 20l/s/km2 and total flow is about 1, 93 billion m3.

Figure 1. Map of study area

  1. DATA ANALYSIS

Water quality problem requires a lot of data categories. In the particular case of this topic is calculation for an unsteady one-dimension flow in the natural canal. The data includes hydrological and hydraulic data, wastewater source data (location and discharge), water quality data (wastewater quality and surface water quality), map, socioeconomic development data, etc.

The data used in the study are  collected from various sources.  Majority of the data  used here such as hydrological y and hydraulic data was  collected from the National Center for Hydrometeorology Forecast. The wastewater sources and water quality data were collected from  the project “Planning water resources allocation and protection in Bac Giang for  the period of 2012 - 2020, vision to 2025”, or collected from the Center for Environmental Monitoring, the Center for Water Resources Technology (MoNRE) and field survey in 2016.

Data of the hydrology stations of  Cau Son and Phu Lang Thuong  on Thuong river as well as Pha Lai on Thai Binh river are also used.

The summary of the data used can be found in Tab. 1 while the  geographic location of the hydrology stations are presented  in Fig. 1.The water quality sampling sites are shown in Fig. 2 (2013) and Fig. 3 (2016).

 

Table 1. Summary of the data used in the study

Data type

Date

Remark

Purpose

Across sections

2000

Thuong river: 32

Modelling

Water level

1/11/2003 - 31/5/2004

Phu Lang Thuong, Pha Lai station

Hydrodynamic calibration

1/11/2012 - 31/5/2013

Hydrodynamic verification

Water discharge

1/11/2003 - 31/5/2004

Cau Son station

 

Hydrodynamic calibration

1/11/2012 - 31/5/2013

Hydrodynamic verification

08/3/2013 - 12/3/2013

Water quality calibration

08/3/2016 - 12/3/2016

Water quality verification

Water quality parameters

 

DO, Temperature, NH4, NO3, BOD5, PO4, Total coliform (Coliform).

Data for running water quality model

Surface water quality

08/3/2013 - 12/3/2013

08/3/2016 - 12/3/2016

Pollutant concentration at: Cau Sơn and Pha Lai station, and some monitoring sites on Thuong river

Data for running water quality model

Wastewater sources

Pollutants concentration, discharge and wastewater source location

Data for running water quality model

Map

 

Thuong river

Mapping

Socioeconomic

2015, 2020, 2030

Status and forecast of population, water demand, wastewater discharge

Assessing and predict water quality

Figure 2. Map of sampling sites in 2013       

                                          

Figure 3. Map of sampling sites 2016

 


  1. METHODOLOGY

The assessment is  undertaken in four different steps. The first step simulates hydraulic and hydrological status  to identify the hydraulic parameters using Hydrodynamic modul (HD) of Mike 11 model. The second step identifies water quality parameters of Advection - Dispersion module (AD) and Ecobal modul including physical parameters and biological parameter as coefficient of diffusion, respiratory, photosynthesis, etc. The third step includes assessment of  water quality in the future based on scenarios and identifying water quality objectives in each river sections. The last step involves assessment of  the capacity of receiving wastewater of Thuong river.

  • Hydrodynamic modul (HD)

The purpose of hydraulic calculation is to find the hydraulic parameters in order to assess water quality in the study areas. The hydraulic parameter is Maning roughness coefficient.

Hydrodynamic modul is built from the equations of continuity and momentum (the ‘Saint Venant’ equations).

The equation of continuity :

The equation of momentum:

Where:

- Q: Discharge (m3/s)

- A: Flow area (m2)

- q: Lateral inflow (m2/s)

- C: Chezy resistance coefficient (m1/2/s)

- α: Momentum distribution coefficient .

- R: Hydraulic or resistance radius (m)

  • Advection - Dispersion (AD) and Ecolab modul

The purpose of running AD and Ecolab modul is to determine the most suitable water quality parameters for the study. Then, using these parameters to predict water quality changes based on the scenarios, thereby assess the capacity of receiving wastewater.

The basic equation of these modules is Advection - Dispersion equation:

Where:

- A: Flow area (m2)

- C: Concentration (kg/m3)

- D: Dispersion coefficient

- q: Lateral inflow (m2/s)

- K: biodegradable coefficient, K is only used when the phenomenon related to biochemical reactions.

ECOlab is accompanied by the water quality template, which is divided into six levels. This study use level 4 + Photphorus + Coliform.

 

  1. RESEARCH RESULTS

5.1. The result of hydrodynamic simulation

Calibrating HD modul aims to finding the hydraulic parameters, by adjusting Manning roughness coefficient so that the  measured and calculated water levels are matched . After adjusting parameters, the HD modul  with time step  of  Δt = 5 minutes, the Manning roughness coefficients ranged from 0,012 - 0,032.

The river network diagram of study area is described in Fig. 4. The results of calibration and verification of hydrodynamic mudul are shown in Fig. 5 - 6.

Figure 4. The river network diagram

Figure 5. Calibration of water level at Phu Lang Thuong station

Figure 6.  Verification of water level at Phu Lang Thuong station

The accuracy of the model was assessed by Nash-Sutcliffe index. It must be mentioned that with higher amount of performance coefficient, the model results are more accurate (B.Razdar et al, 2011). The NASH coefficient at Phu Lang Thuong station is 98% (Calibration) and 94% (Verification). Thus, it is possible to use HD modul as input data for AD and Ecolab modul (water quality simulation).

5.2. The result of water quality simulation

Water quality data observed in March 2013 and in March 2016 are used for calibration and verification water quality modul respectively.

  • The calibation results are presented in Fig. 7 - 13.

Figure 7. Calibration of DO concentration

Figure 8. Calibration of NH4 concentration

Figure 9. Calibration of Temperature concentration

Figure 10. Calibration of NO3 concentration

Figure 11. Calibration of BOD5 concentration

Figure 12. Calibration of PO4 concentration

Figure 13. Calibration of Total Coliform concentration

The calibration of water quality modul aims to find the optimal model parameters for study area. The reliability of the parameters is shown by the calibration results as the deviation between measured data and simulated data, as follows: The deviation of temperature is from 0.08 - 0.22 degrees; DO: 0,67mg/l - 0,24mg/l; NH4: 0,01mg/l - 0,14mg/l, NO3: 0,01mg/l - 0,06mg/l, BOD5: 0.1 mg/l - 0.2mg/l, PO4: 0.005mg/l - 0.01mg/l , Coliform: 170 MNP/100 ml - 680 MNP/10ml. All these deviation are under the allowable limit  (10%).

To assess the accuracy of parameters found in the calibration process, we continue using these parameters for the varification step with surveyed data in 2016.

The  verification results are presented in Figure 14 - 20.

Figure 14. Verification of DO concentration

Figure 15. Verification of NH4 concentration

Figure 16. Verification of Temperature concentration

Figure 17. Verification of NO3 concentration

Figure 18. Verification of BOD5 concentration

Figure 19. Verification of PO4 concentration

Figure 20. Verification of Total coliform concentration

The results indecated that deviation range of temperature is 0.1 - 0.3 degrees Celsius; DO: 0.2 mg/l - 0.8 mg/l; NH4: 0,01mg/l - 0,03mg/l; NO3: 0,18mg/l - 0.45 mg/l; PO4: 0,01mg/l - 0.06 mg/l; BOD5: 0.14 mg/l - 0.52 mg/l, Coliform: 11.7MNP/100ml - 165,2MNP/10ml.

Deviation between measured data and simulated data is under the allowable limit (10%). Thus, can use the model to forecast water quality in the future.

5.3. Prediction of water quality of Thuong river by MIKE 11 model

Based on the planning on economic - social development and water resources in 2020 and 2030 of Bac Giang, predict the wastewater discharge to Thuong river in 2020 and 2030 as follows:

Table 2. Prediction of wastewater discharge  

to Thuong river in 2020 and 2030

 

Wastewater discharge
(m3/day)

Year

Domestic

Industry

Agriculture

2020

43.623,28

963.904

41.507

2030

48.260,94

5.550.411

77.488

Using the hydraulic and water quality parameters found above and wastewater discharge forescasts in 2020 and 2030 (Tab. 2), predict water quality of Thuong river under 3 scenarios:

- Scenario 1: The amount of waste water in the basin increased according to plan, but untreated.

- Scenario 2: The amount of waste water in the basin increased according to plan, but 30% was treated.

- Scenario 3: The amount of industrial waste water in the basin increased according to plan, but 70% was treated and achieve the industrial wastewater standard.

The simulated concentrations of pollutants are compared with the National technical regulation on surface water quality, 2015, A2 colum (for domestic purpose).

The results of water quality prediction  under 3 scenarios are shown below:

Figure 21. DO concentration  in 2020

Figure 22. DO concentration  in 2030

Figure 23. NH4 concentration in 2020

Figure 24. NH4 concentration  in 2030

Figure 25. N03 concentration in 2020

Figure 26. N03 concentrationin 2030

Figure 27. BOD5 concentration  in 2020

Figure 28. BOD5 concentration in 2030

Figure 29. PO4 concentration  in 2020

Figure 30. PO4 concentration  in 2030

Figure 31. Coliform concentration  in 2020

Figure 32. Coliform concentration  in 2030

The simulated results of  water quality of Thuong river in 2020 and 2030 indicated that:

  • Scenario in 2020:

- DO: DO concentration under  3 scenarios are within the allowed limit .

- NH4: NH4 concentrations are mostly beyond the standard, from 1,9 to 3,27 times (scenario 1); 1,2 to 2,4 times (scenario 2) and less than 1.7 times (scenario 3). In particular, the water quality at Pha Lai station is within the standard in both 3 scenarios.

- NO3: In scenario 1 and 2, the concentration of NO3 mostly exceeds the standard. At some points B1, B6, B8, B18 and B20, the concentrations exceed negligibly. The remaining points has NO3 concentrations exceed less than 2.5 times.

- BOD: BOD concentration is within the standard in scenario 3, and does not significantly exceeded in scenarios 1 and 2, except the concentrations at point B11 exceed standard 2 times in 3 scenarios.

- PO4: PO4 concentrations of scenario 1 are higher 4 times in comparision with standard while 0,5 - 3 times in scenario 2 and 3. In particular case of point B22, PO4 is within the permitted standard.

- Coliform: no sign of coliform contamination in 3 scenarios.

  • Scenario in 2030:

- DO: DO concentrations are within the allowed limit for 3 simulated scenarios.

- NH4: The values of NH4 exceed 12 times compared with standard in scenario 1 and 0,5 - 8 times in 2 remaining scenarios.

- NO3: NO3 concentrations are higher than the standard in 3 scenarios except the point of B18 and B22.

- BOD: BOD exceededs 2.8 times in scenario 1 and 2, but within the standard in scenario 3.

- PO4: The value of PO4 exceeds standard in 3 scenarios, from 2,5- 15,2 times in scenario 1; 3,8 - 10,4 times in scenario 2 and 1,1 - 3,55 times in scenario 3.

- Coliform: no sign of coliform contamination in 3 scenarios.

CONCLUSION

This paper presents the results of the simulation of hydrodynamic and water quality modeling of Thuong river by MIKE 11, and then predict water quality in 2020 and 2030.

The calculated results have high accuracy (reliability from 92% - 98% for HD modul and error under 10% for water quality modul), so it’s valuable to be used for predicting water quality in the future.

Water quality simulation of the Thuong river for years of  2020 and 2030 showed that the water has signs of contamination. The pollution levels are different along the river. The most polluted locations are at Bac Giang city and Yen Dung district, due to Hoang Van Thu paper  factory, Ha Bac fertilizer plant and some other facilities. The main  contaminated parameters are PO4 and NH4 with concentrations reach up to 12 and 15,2 times higher than the standard. The values of BOD5 and NO3 are lighter pollutants, DO and Coliform have no sign of contamination.

Assessing the capacity of receiving wastewater of Thuong river will be presented in the next report.

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