Forecasting the water quality and the capacity of receiving wastewater of the Dong Nai river up to 2020

Journal of Science and Technology 54 (2A) (2016) 141-148 FORECASTING THE WATER QUALITY AND THE CAPACITY OF RECEIVING WASTEWATER OF THE DONG NAI RIVER UP TO 2020 Le Quoc Tuan 1, * , Ngo Thi Kieu Diem 2 1 Faculty of Environment and Natural Resources, Nong Lam University, Linh Trung Ward, Thu Duc District, Ho Chi Minh City, Vietnam 2 Dong Nai Department of Natural Resources and Environment, Dong Khoi Street, Tan Hiep Ward, Bien Hoa City, Dong Nai, Vietnam * Email: quoctuan@hcmuaf.edu.vn Received: 1 April 2016; Accepted for publication: 15 June 2016 ABSTRACT Dong Nai river, the largest river system in the South East region, flows through five provinces in the South East area. Dong Nai river serves water for living, production, irrigation, aquaculture, navigation, and hydropower. It receives a huge impact from the natural and artificial elements, such as municipal wastewater from residential areas and urban centers; industrial wastewater from industrial zones, toxic wastewater from agricultural activities, etc [4, 6, 7, 12]. Therefore, the prediction of water quality change and the capacity of receiving wastewater are very essential in environmental protection for Dong Nai river. The study results showed that the water quality of Dong Nai river is currently achieved to the standard requirement and the using purposes. However, there were some sections where had locally polluted signs and had not be used (such as Dong Nai river in the section 3). Predictably up to 2020, pollutant load will increases, however, the water quality of Dong Nai river is still achieving the fundamental purpose of water supply, except TSS which, water from the area below Tri An damp to Dong Nai bridge, is not reached the regulation permit in the beginning and ending of rainy season. To protect the water of Dong Nai River, the optimal solution is necessary to collect and treat all wastewater from industrial, domestic, livestock and medical activities to get the standard permission before discharged into Dong Nai river. At the same time, considering the capacity of receiving wastewater on the each section of Dong Nai river is conducted to allow new investment projects and license of wastewater dischargement. Keywords: Dong Nai river, water quality, wastewater, receiving capacity 1. INTRODUCTION Dong Nai province is located in the southern key economic region, one of the provinces with economic growth, highly investment attraction, rapid industrial development, including industry and services, agriculture. Dong Nai province has been launched many industrial parks, Le Quoc Tuan, Ngo Thi Kieu Diem 142 clusters such as Bien Hoa 1, Bien Hoa 2, Amata, Loteco, Tam Phuoc... According to report of the Department of Natural Resources and Environment in 2015, Dong Nai province has 31 industrial zones and 27 industrial parks which have built wastewater treatment plants. Besides the waste water from the industrial park also has a huge amount of waste water from hospitals, residential areas [1, 2]. The process of economic and social development, the surface water are threatened directly by the waste generators from daily activities (urban, residential areas ...) to development activities as the industries (industrial, manufacturing factories ...), husbandry, fisheries, ... almost being discharged directly into water sources. Contaminated surface water affects the self- cleaning ability, declining water quality, also greatly affects human health and the environment, resulting in causing a negative impact [13, 14] on the socio-economic development process. This is the great challenge for socio-economic development of Dong Nai province [4]. Therefore, assessing the quality of present water sources, calculating the load of pollutants into the river, as well as forecasting the water quality and the capacity to receiving wastewater by Dong Nai river to 2020 in order to offer the unified management solutions, synchronization and partition of discharge to ensure water quality and socio-economic development. This study is essential to serve the exploitation, usage and protection of water resources sustainably for the Dong Nai river in the whole province. 2. MATERIALS AND METHODS 2.1. Assessing the water quality and partitioning the receiving zone The surface water quality assessment is carried out according to Decision No. 879/QĐ- TCMT dated 01/07/2011 on the issuance of the manual calculation of water quality indicators in order to assess rapidly the surface water quality. To determine the quality of each specific areas, water quality index (WQI) of each river section and WQI of each monitoring sites are calculated [15]. In addition, the comparison of the pollutant concentration to 08-MT: 2015/MONRE was applied to assess concentrations of some pollutants. Application of Decision No. 16/QĐ-UBND dated 03/19/2010 for partition of receiving industrial wastewater and emission in Dong Nai province to determine the regulations for each section of Dong Nai river [8] and previous result to confirm sections in partitioning of wastewater receiver [12]. 2.2. MIKE 11 modeling MIKE 11 software [3, 9] and analysis [5, 10, 11] applied for forecasting water quality and receiving capacity of wastewater up to 2020. Update data on pollution load into the river can forecast the receiving capacity of wastewater to Dong Nai River up to 2020. Based on hydraulic model of Dong Nai River, on the sources of the waste [2, 9, 10], a concentration scenario, the flow of the waste stream and predictive models of water quality was built for Dong Nai river. The whole 29 streams with over 40 compute nodes and River Network tools are used for Mike 11 model to build up hydraulic diagram calculations. Cross-sectional data of models including measurements of the 357 cross-sections have been transferred to digital terrain data format used in Mike 11. Mike 11 was applied for 3 scenarios and scenario 2 was selected for wastewater management. Data used for Mike 11 were collected from the Department of Natural Resources and Environment, Dong Nai province from 2010 to 2014. Forecasting the water quality and the capacity of receiving 143 Upper margin of the hydraulic model includes: (1) Margin at section 0: The discharge of Tri An hydropower and average flow of Be river; (2) Margin of flow on La Buong river: The average of monthly flow for many years (1978-2000) at hydrological stations; (3) Margin of flow of Nuoc Trong stream: average flow for years Qaverage = 5.58 (m 3 /s) Lower margin of the hydraulic model includes: (1) Margin of water levels in Vung Tau (transmission calculation on entrance Long Tau, Dong Tranh, Soai Rap); (2) Margins of flow is the same as upper’s. 3. RESULTS AND DISCUSSION 3.1. The water quality of Dong Nai river Collecting and analyzing the monitoring data from the Department of Environment and Natural Resources through the 2011, 2012, 2013 [1, 2] at the 19 monitoring sites; according to Decision No. 16/2010/QĐ-UBND dated 19/03/2010 on the partition of wastewater and industrial receiving in Dong Nai province were used to assess the quality of Dong Nai river in each sections as follows: Section 1: from Nam Cat Tien wharf to ferry 107, Phu Ngoc commune, Dinh Quan district; Section 2: From the lower of Tri An reservoir, confluence of Be river and Dong Nai river, Vinh Cuu district to Ba Mieu wharf, Bien Hoa city; Section 3: From Hoa An bridge, Hoa An commune, Bien Hoa city to Dong Nai Bridge, Long Binh Tan ward, Bien Hoa city; Section 4: From the lower of Dong Nai bridge, Long Binh Tan ward, Bien Hoa city to confluence of Cai Mep and Go Gia rivers, Phuoc An commune, Nhon Trach district. The monitoring data and calculating of WQI show that the water quality of Dong Nai river, basically meets regulations for each water use purpose. Water quality of Dong Nai river in sections 1, 2, reaches regulation for water supply, section 3 for water supply, but sometimes in the rainy season (in months 7, 8, 9) water quality has shown significant decline. Section 4 meets regulation for irrigation and aquatic conservation. 3.2. Waste sources to Dong Nai river Table 1. Waste sources to Dong Nai river No Waste sources Total of flow Flow (Q m3/day) Q m3/day Section 1 Section 2 Section 3 Section 4 1 Health facilities 2,467 16 61 1,820 570 2 Factories outside industrial parks 66,497 2,441 17,710 23,910 22,436 3 Domestic activities 89,070 319 1,297 86,519 935 4 Husbandry activities 586 39 198 25 324 5 Markets 589 5 194 280 110 6 Industrial parks 56,268 24 4,600 40,908 10,736 Total 215,477 2,844 24,060 153,462 35,111 Dong Nai River is receiving most of the wastewater from factories, urban areas, residential areas, major industrial parks in Dong Nai province. According to data obtained from the Department of Natural Resources and Environment, Dong Nai river is receiving wastewater flow 215,477 m 3 /day [2], this is the largest received wastewater. In which, wastewater from health Le Quoc Tuan, Ngo Thi Kieu Diem 144 facilities with average flow of 2,467 m 3 /day, from urban and residential areas with 89,070 m 3 /day, from livestock operations about 586 m 3 /day, from markets, supermarkets, trade centers with an average of 589 m 3 /day, from 11 industrial zones with 56,268 m 3 /day, and from manufactories about 66,497 m 3 /day (Table 1). In industrial zones, there are wastewater treatment plants and wastewater were controlled before releasing to Dong Nai river. Wastewater from the other sources have not been treated and released directly to Dong Nai river, especially wastewater from urban regions and agricultural sectors (husbandry) which mainly affect water quality of Dong Nai river. 3.3. Waste load to Dong Nai river According to the quality analysis and relevant calculations for concentration of pollutants, there are selected parameters: BOD5, COD, total N, P total and TSS. The load of pollutants goes down to Dong Nai river was shown in Table 2. Table 2. Load of pollutants in wastewater in 2013. No. Waste sources Q in 2013 (m3/day) Load (kg/day) BOD5 COD Total N Total P TSS 1 Health facilities 2,467 35 113 41 12 145 2 Factories outside industrial parks 66,497 1,190 4,360 1,850 79 4,030 3 Domestic activities 89,070 5,700 3,296 1,158 89 9,709 4 Husbandry activities 586 151 333 170 41 245 5 Markets 589 89 100 31 19 121 6 Industrial parks 56,268 800 2,579 1,073 114 3,393 Total 215,477 7,965 10,781 4,323 354 17,643 3.4. Forecasting load to Dong Nai river in 2020 It is aiming to forecast the Dong Nai river’s water quality to 2020, there are three given scenarios, calculate the pollution load of waste sources into Dong Nai River in the current period, and forecast to 2020. Five parameters of water quality were selected as BOD, COD, total nitrogen, total phosphorus, TSS to calculate and build predictive models. These scenarios are based on the actual conditions of the provincial planning and economic development. Three scenarios were shown as follows. Scenario 1. The quality of waste water into Dong Nai river as current status: the obligation for the legal regulations of waste generators; the maintaining of the management of environmental protection; increasing economy as planned. Therefore, wastewater flow increases with economic development, collection and wastewater treatment is not much changed, the wastewater systems continue its current operation, large urban areas have not developed the domestic wastewater treatment, livestock mostly untreated before being discharged into the receiver, the concentration of contaminants does not change. Calculated pollutant loads by 2020 were estimated in Table 3. Scenario 2. Suppose that by 2020, water flow increased as planned, wastewater in urban areas, production establishments, animal husbandry, health,...are treated to meet 08- MT:2015/MONRE (column B) before being discharged into the receiving water of Dong Nai river. Forecasting the water quality and the capacity of receiving 145 Scenario 3: Based on the planning of social and economic development in Dong Nai province, the implementation of environmental protection activities in Dong Nai province according to the Environmental Protection project of Dong Nai province until 2020. Table 3. Load of pollutants in wastewater to 2020 in scenarios (1, 2 and 3). No. Waste sources Q in 2020 (m3/day) Load (kg/day) BOD5 COD Total N Total P TSS 1 Health facilities 5,297 56 271 47 32 429 2 Factories outside industrial parks 108,058 1,934 7,089 3,004 130 6,548 3 Domestic activities 125,326 12,783 14,287 1,792 226 16,982 4 Husbandry activities 59,409 15,328 33,744 17,217 4,182 24,803 5 Markets 1,296 200 316 77 49 292 6 Industrial parks 320,498 4,551 14,679 6,122 641 19,358 Total (Scenario 1) 619,884 34,852 70,386 28,259 5,260 68,412 1 Health facilities 5,297 265 530 265 53 530 2 Factories outside industrial parks 108,058 5,403 16,209 4,322 648 10,806 3 Domestic activities 125,326 6,266 12,533 1,253 1,253 12,533 4 Husbandry activities 59,409 2,970 5,941 1,782 356 5,941 5 Markets 1,296 65 194 52 8 130 6 Industrial parks 320,498 16,025 48,075 12,820 1,923 32,050 Total (Scenario 2) 619,884 30,994 83,482 20,494 4,241 61,990 1 Health facilities 5,297 159 265 159 32 265 2 Factories outside industrial parks 108,058 1,837 4,538 1,189 216 3,026 3 Domestic activities 125,326 3,760 6,266 627 752 6,266 4 Husbandry activities 59,409 1,782 2,970 891 238 2,970 5 Markets 1,296 39 65 39 8 65 6 Industrial parks 320,498 9,615 24,037 6,410 1,282 16,025 Total (Scenario 3) 619,884 17,192 38,141 9,315 2,528 28,617 The calculated results show that load of pollutants flowing into the Dong Nai river in scenario 3 is the lowest, this is the perfect scenario for the future. Thus, the amount of pollutants discharged rise until 2020, if having no method to reduce and regulate the discharge of wastewater into water receiver, Dong Nai river will be under stress of pollution. Modeling results and monitoring results at three locations are nearly fixed, average error fluctuating from 10 to 19 %. 3.5. Water quality forecasting The calculation results for load of waste sources into the Dong Nai river shows that scenario 3 is the most ideal, pollution load into the river is the lowest. Assessing the current state of the Dong Nai river’s water quality indicated that Dong Nai river has reached the water use. Therefore, research is focusing on building predictive models for scenario 1 and scenario 2 up to 2020. The load- receiving sites, analyzing and evaluating for pursuing the water use purpose, site 1, site 2 compared to standard 08-MT:2015/MONRE 2 Figure 1. Sites for MIKE11 application Le Quoc Tuan, Ngo Thi Kieu Diem 146 (column A2) and site 3 compared to standard 08-MT:2015/MONRE (column B2). According to the model results, the concentration of TSS in the location and the scenario is as follows: Under scenario 1: At sites 1, 2, largest TSS concentrations in the range of 40-60 mg/L which exceeds regulation on the start and end of the rainy season months, the remaining months meet standards; At site 3, the highest concentration of TSS in March, 230 mg/L exceeds permitted standards, the remaining months meet standard; Under scenario 2: At sites 1, 2, largest concentration of TSS in the range of 40 - 60 mg/L over regulation on the start and end of the rainy season months, the remaining months meet standards; In site 3, the highest TSS concentrations in the range of 59 - 61 mg/L reaching regulations and lower than scenario 1. Therefore, in the case of the management under scenario 2, the maximum load of TSS at sites 1, 2 in the dry season (from January to June) ranges from the minimum 1,000 (tons/day) and maximum in October with 7,000 (tons/day), the average maximum load for the whole year is 3,500 (tons/day). In rainy season, TSS concentrations have exceeded the standard 08-MT: 2015/MONRE (column A2), that should not be admitted for TSS load. At site 3, maximum load reached 3,200 tons/day in January, average 1,800 (tons/day). The maximum load is generally tended to increase during the rainy season. At site 3, due to the strong tides, the maximum load was fluctuating. The result of the modeling scenarios shows the Dong Nai river is still able to receive BOD, TSS, total N, P total. Noted that scenario 1, the concentration TSS and COD waste in the dry season from Dong Nai bridge 1 km downstream to Long Tau area exceeded standards. This section is no longer capable of receiving for TSS and COD. From the results of scenario 1, the management of waste discharge and pollution control remain the same as the present, and pollutant concentrations will be high, water quality will be contaminated (COD, TSS over standard). In scenario 2 by 2020, with good management, the wastewater treatment plant work well to reach standards 08-MT: 2015/MONRE (column B), water quality is better and achieve the water use purposes. Therefore, scenario 2 is the best choice for environmental management. 3.6. Partition for water receiving of Dong Nai river Based on the modeling results for water quality of scenario 2 by 2020, there are partitions of discharge areas as follows: - Region 1, from the Tri An dam to Dong Nai Bridge 1 km downstream: capacity of receiving wastewater with total BOD 1,000 tons/day, COD 2,100 tons/day, TSS 3,500 tons/day, total N total 600 tons/day, total P 22 tons/day. - Region 2, from Dong Nai bridge (1 km downstream) to the Dong Nai river lower basin, can receive maximum BOD 500 tons/day; COD 900 tons/day; TSS 1,800 tons/day; total N 300 tons/day; total P 1.4 tons/day. Based on partition for receiving wastewater, authorities have licensed for discharging wastewater into the Dong Nai river. 4. CONCLUSIONS Load of pollutants into Dong Nai river is huge. According to statistics, total daily discharge of wastewater into the river about 215,477 m 3 , the largest source from the industrial zones and Bien Hoa city. This is the main reason causing water quality decline. Forecasting the water quality and the capacity of receiving 147 Under scenario 2, the forecast by 2020, Dong Nai river’s water quality from Tri An dam to Dong Nai bridge meets standards, achieves the purpose of water supply for the parameters of BOD, COD, total N, total P. TSS, but in the rainy season, TSS exceeds standards do not meet water supply purposes. Water quality in Dong Nai river lower basin, Nhon Trach district, achieves the purpose of navigation and aquatic living protection. In order to protect Dong Nai river’s water quality, it is necessary to implement proposed solutions. In particular, implementation of priority measures to collect and treat all wastewater from urban based on partitions of wastewater receiving; localities in the Dong Nai river basin need a unity of water using purpose and issue regulations on wastewater discharge for each area accordingly. REFERENCES 1. Center for Environmental Monitoring and Engineering of Dong Nai province - Report ―Environmental monitoring of water quality of Dong Nai river, Dong Nai province in 2010‖, 2010. 2. Center for Environmental Monitoring and Engineering of Dong Nai province - Report ―Environmental monitoring of surface water quality in Dong Nai province in 2012 and 2013‖, 2013. 3. Danish Hydraulic Institute - Mike flow model, Hydrodynamic module: Scientific Documentation, 2007. 4. Do Tien Lanh, Ngo Duc Chan - Project report ―Integrated management of water resources in Dong Nai river basin, KC08-10 program, Ministry of Science and Technology, 2010. 5. Moriasi D. N., Arnold J. G., Van Liew M. W., Bingner R. L., Harmel R. D., Veith T. L. - Model evaluation guidelines for systematic quantification of accuracy in watershed simulations, Trans ASABE 50 (2007) 885–900. 6. Nguyen Ngoc Anh, Do Duc Dung - Provincial project report ―Research, assessing the exploitation status for planning and management of surface water in Dong Nai province‖, Dong Nai Department of Science and Technology, 2006. 7. Nguyen Ky Phung - Research report ―Determining the maximum load for the building of discharge limits on the Saigon river (from Thu Dau Mot to Nha Be)‖, 2009. 8. People’s Committee of Dong Nai province - Decision No. 16/QĐ-UBND dated 03/19/2010 for partition of receiving industrial wastewater and emission in Dong Nai province to determine the regulations for each section of Dong Nai river, 2010. 9. Rogers P. P. and Fiering M. B. - Use of systems analysis in water management. Water Resources Research 22 (9) (1986) 146S-158S. 10. Rosegrant M. W. et al - Integrated economic-hydrologic water modeling at the basin scale: The Maipo river basin, Agricultural Economics 24 (1) (2000) 33-46. 11. Thompson I. R., Green A. I., Kingston D. G., Gosling S. N. - Assessment of uncertainty in river flow projections for the Mekong River using multiple GCMs and hydrological models, Journal of Hydrology 486 (2013) 1–30. Le Quoc Tuan, Ngo Thi Kieu Diem 148 12. The Southern Division for Water Resources Planning and Investigation (SDWRPI) - Project report ―Investigation and assessment of wastewater discharge and receiving capacity in Dong Nai province, 2013. 13. Todd M. C., Taylor R. G., Osborn T. J., Kingston D. G., Arnell N. W., Gosling S. N. - Uncertainty in climate change impacts on basin-scale freshwater resources—preface to the special issue: the QUEST-GSI methodology and synthesis of results, Hydrological Earth System Science 15 (2011) 1035–1046. 14. Tran Hong Thai, Tran Thuc - Impacts of climate change on the flow in Hong—Thai Binh and Dong Nai river basins, VUN Journal of Science, Earth Science 27 (2011) 98–106. 15. Vietnam Environment Administration - Decision No. 879/QĐ-TCMT dated 01/07/2011 on the issuance of the manual calculation of water quality indicators in order to assess rapidly the surface water quality, 2011.