INTRODUCTION
The project “Survey on water quality changes regarding capacity of the Red River Basin (RRB) water resources in receiving waste water” is currently being carried out by the Institute of Water Resources Planning. The project commenced in 2001 and is planned to be completed in 2005. The key objectives of the project are to observe trends and changes in water quality in the mainstream and tributaries in the RRB, find out reasons and locations of surface water pollutants, assess capacity in receiving effluents into the RRB water sources serving water resources development planning??; manage environment concerns, and issue licenses for waste water discharges and water use in the whole river basin.
The Red river is an international river, influenced by upstream water resources and development activities within China. This is a huge river basin in which occurs a rather high socio-economic growth rate and changes at some places, therefore regular and adequate observations of water quality changes in the mainstream are indispensable.
This project therefore involves a baseline survey of large scale and complexity, expanding both in space and time.
The project area is the portion of the RRB in Viet Nam’s territory, but mainly the mainstream. The key points that have been surveyed in detail for installation of observation stations are as follows (see also the enclosed map):
- Selected controlling points in border rivers which flow into the RRB,
- Confluences of tributaries to the mainstream,
- Selected points in the mainstream where effluents of mine exploitation units or residential areas enter,
- Water intakes for water users (domestic, irrigation, etc) and drainage points.
Observation periods concentrate in months when water quality has important changes, flows are small, and water use demands are large.
The project is ongoing in its 4th year (2004) with the aims of continuing observation of water quality at proposed installation points, reviewing locations and regimes in order to recommend prompt adjustments so that the project could have an optimal observation network for regular monitoring in the next phase when the project is completed.
METHODOLOGY AND CONTENTS
1. CONTENTS
Collect information and documents relating to water quality changes including current status of economic sectors, sub-sectors in the project area that affect water quality to understand degree of utilization and waste water discharges.
Survey to define the observation network and take samples for analysis. Sample analysis is done according to the methodology stipulated in the Viet Nam Standards 1995 and in reference to internationally accepted standards.
Analysis data in periods and years are collated and stored in a database. Data within this database are used to carry out calculations, and create diagrams and charts showing changes in water quality parameters in space and time.
2. METHODOLOGY FOR MEASUREMENT AND WATER SAMPLE ANALYSIS
Sample taking and field measurements
Sampling and field measurement procedures are applied in accordance with regulations issued by the Ministry of Science, Technology and Environment (MOSTE). Each water sample has its own curriculum including map of sampling location, descriptions of climatic conditions, environment status affecting water quality, and especially pollutant sources at sampling time.
Some changeable parameters such as temperature, pH, conductivity, dissolved oxygen, turbidity are measured at fields by respective meters. Field measurement meters used during sampling include the following:
- Temperature: using a dissolved oxygen meter or conductivity meter (accuracy at 10-2 (WTW type of Germany)),
- pH: using a pH meter with accuracy at 10-2 (Metrom type of Switzerland),
- Conductivity: using a conductivity meter with accuracy at 10-2 (WTW type of Germany)
- DO: using a DO meter with accuracy at 10-2 (YSI type of US),
- Turbidity: using a turbidity meter EE 70 type of England with accuracy at 10-1
Sample analysis in laboratory
Parameters analyzed in the laboratory included 19 chemico-physical parameters, 3 micro-organism parameters in addition to interrupted analysis of 4 parameters for heavy metals and 4 parameters for plant protection chemicals (See Annex 1).
Analysis methods: Given available laboratory equipment, technical capabilities in satisfying project objectives, analysis of water quality parameters is done applying modern standard methods of high accuracy (10-2 to 10-3 ppm). So the analyzed data can be used for water quality assessment for different purposes. The methods used for the laboratory analysis of parameters are described below:
- Suspended matters: weighting method, drying at 105°C using German analysis scale at accuracy of 10-4g,
- Ca2+: using Trilong B title method with black E. CromT as indicator,
- Mg2+: using title method
- So42-: using weighting method, precipitating with BaCl2 and quantifying using German analysis scale at accuracy of 10-4g,
- Kali, Natri: using fire photometer method, Jenway of England of accuracy of 10-3 ppm,
- Chlorine: using title method with AgNO3 and Kalicromat as indicator,
- Total iron: using photometer method, UV-Vis-Shimadzu of Japan, accuracy of 103 ppm and sunfore salicylic as indicator,
- NH4+: using photometer method, UV-Vis-Shimadzu of Japan, accuracy of 10-3ppm,
- NO2-: using photometer method, UV-Vis-Shimadzu of Japan, accuracy of 10-3ppm,
- NO3-: using photometer method, UV-Vis-Shimadzu of Japan, accuracy of 10-3ppm,
- PO43-: using photometer method, UV-Vis-Shimadzu of Japan, accuracy of 10-3ppm,
- COD: using Permanganate kali method
- BOD: using piezometer method, WTW BOD equipment of Germany,
- Coliform: using filter membrane method, growing bacteria at 37°C in incubator Memmert of Germany, error 0.5°C,
- Fecal coliforms: using filter membrane method, growing bacteria at 42°C in incubator Memmert of Germany, error 0.5°C,
- Coli ferfrigens: using Winsonblair method, growing bacteria at 37°C in incubator Memmert of Germany, error 0.5°C
METHODOLOGY AND CONTENTS
1. RESULTS OF FIELD SURVEYS AND WATER SAMPLING
Thorough field surveys are very helpful for timely adjustments to the monitoring network so that pollution degrees at special points and their changes can be monitored. For example, in the Nhue irrigation scheme, water pollution happens very intricate because it is influenced by effluents of Hanoi city. Then this pollution spreads to Ha Nam province in months of the dry seasons affecting domestic water supply in Ha Nam province. As consequence, the project has been supplemented with an additional sampling point at Luong Co sluice in Nhue river. In contrary, there is not any sudden change in Da Bach river during observations so regular observations at this point has been stopped in the project.
2. RESULTS OF SAMPLE ANALYSIS IN LABORATORY
Annually, about 180 water samples for the midlands and plains, 24 water samples for the border areas and 84 water samples for the two special gauging stations (Hanoi and Pha Lai hydrological stations) have been analyzed in the project.
Total analyzed parameters are 22 including 19 chemico-physical and 3 micro-organism ones. They are basic parameters necessary for assessment of water pollution changes in the river basin. All water samples have been taken, measured and analyzed in accordance with prevailing regulations by former MOSTE (current Ministry of Natural Resources and Environment). Analysis results have been synthesized, then checked by competent agencies and concluded as sufficiently reliable and accurate for water environment planning and management and also for other purposes
Analyzed data are rather continuous, they are collected in months of the dry seasons and 2 months of the rainy seasons from 2001 to 2004 so they can be used for assessment of water quality changes in months of the dry and flood seasons respectively when water quality has known considerable changes as receiving effluents. Analyzed data are then systematized and stored to facilitate data access and utilization as well as change assessment at different views.
Results of measurement and analyses have been updated, calculated and interpreted into diagrams and charts for assessment of water quality changes in space and time.
Measured and analyzed data are reliable and can be used for assessment and classification of water sources serving water resources development planning projects, especially for monitoring surface water quality changes in view of capacity to receive effluents into RRB water resources, this can be used as bases for licensing for water use and waste water discharges.
Assessment and classification of water quality are done basing on analysis results, on requirements and purposes of water uses for each sectors, each areas in comparison to the TCVN 5942-1995 for surface water standards, and water discharge standards (for industrial effluents).
Water quality changes are assessed according to measurement points, changes along the river and in months measured in years.
3. GENERAL ASSESSMENTS ON WATER QUALITY CHANGES
Water quality changes are very complex as water quality changes depend on various factors such as natural conditions, hydro-meteorological conditions, and especially socio-economic development conditions in areas where emission sources exist. Water quality always changes in space and time that is the reason why environmental changes affecting water sources have been regularly surveyed and updated in this project in combination with field surveys and measurements as bases to assess water quality changes in each sub-areas.
Water quality changes in the river
In the Red river mainstream: There are 6 measurement points in the mainstream, i.e., Coc Leu bridge, Cam Duong commune downstream of Lao Cai town, Tuan Quan hydrological station, Viet Tri confluence, Ha Noi hydrological station, and Vu Dien wharf. Red river receives a large volume of industrial and domestic waste water, especially at the Thao river section from Lam Thao to Viet Tri confluence, Tuan Quan hydrological station receives waste water of Yen Bai town, Ha Noi hydrological station receives waste water of Bai Bang, Lam Thao super phosphate and Viet Tri industrial zones. In the dry season, water in effluents increases whilst dilution capacity is limited resulting in water pollution localized at that river reach and too bad water quality for domestic and production demands.
At the Red river reach from Viet Tri confluence to downstream, the river does not directly receive effluents of Ha Noi city (when Yen So pumping station does not work) or those of large industrial zones. After confluence with Red River, Lo river has high dilution capacity to purify itself. Therefore water quality in Red river downstream is better than in the reach via Lam Thao – Viet Tri but the downstream reach is still lightly contaminated in the dry season. Besides, Yen So pumping station operates to drain waste water of Ha Noi into Red river in the flood season but it does not much affect Red river water quality as the river discharges are too large at that moment and water is not used for domestic or production purposes but mainly flows to the sea. However it is necessary to carry out survey on pollutant sources, monitor Red river water quality in the downstream reach to prevent increasing pollution potentials, particularly in the dry season. Pollutants in the Red river are mainly suspended matters, organic matters, NO2-, and coliforms. Pollution is locally and instantly characterized.
It is noted that Red river water sources from China flowing into Viet Nam territory at the border in Lao Cai province have signs of being polluted that needs to be further monitored, emission sources to be surveyed, water quality changes to be overseen to timely predict bad water quality changes to secure water use in downstream.
In the Da mainstream: Measurements and surveys at 4 points (from the border to downstream) i.e., Muong Te, Ma Lu Thang border gate, Ben Ngoc hydrological station and Trung Ha ferry have been carried out. Measurement results of some parameters have shown that not like the Red river mainstream, Da river water quality in middle and downstream reaches does not much change because it does not receive domestic waste water effluents from urban, and industrial areas and the river flows are big. Nevertheless it is noted that Da river water sources from China flowing through Muong Te, Nam Na borders at Ma Lu Thang border gate are not in good quality resulted from gold exploitation and processing in China territory and even along the border with Viet Nam. Those activities are ebulliently ongoing on the river along the border. The river water at that reach is very turbid transporting sediments and mineral sands as well as sifting chemicals. It is therefore necessary to strictly oversee and survey water sources from China at the border in parallel with instructions to local people in safe and appropriate utilization of Da water sources for domestic purposes. At the moment it is recommended not to use Da water sources at the border for domestic use purposes.
Although it still receives domestic and industrial effluents during its flowing course to downstream, Da river water in the middle and downstream reaches looks more transparent than at the border because those domestic and industrial effluents are not many thanks to deposition and self-purification so water quality at the middle and downstream reaches are good enough for domestic and production supply. Again, it is worth paying special attention to the border reach at Muong Te and Ma Lu Thang border gate where wastes of mine exploitation from China must be permanently monitored in order to timely inform local people who use that water source for their domestic use.
In the Cau river mainstream: Measurements have been carried out at 3 points (Thac Huong, Tra Vuon (Luu Xa) and Nhu Nguyet (Dap Cau) bridges. Those points are exactly points receiving industrial effluents from Thai Nguyen city and Bac Ninh town. Waste water in this area is relatively large but waste water discharges are not stable. Quality of waste water is various. Sampling periods are not coincided with maximum discharging periods so analysis results are not typical. Measurement and survey results, however, show that Cau River water at the reach from Thac Huong weir to Tra Vuon bridge is locally polluted, especially in the dry season when effluents flows in and in June (early rainy season). From Dap Cau, water is flowing via a long distance (30 km) where wastes are diluted and deposited so the river is purified itself and water quality is much improved. Then the river continues receiving waste water from Dap Cau industrial zone but its quality is still better than the reach in Thai Nguyen. The most polluted measurement points are Thac Huong weir and Tra Vuon bridge with organic matters, NO2-, suspended matters and coliforms as typical pollutants.
In Day river basin: there are 12 key measurement points representing water quality in each tributary and in some urban domestic and industrial drainage channels in Day river basin. Receiving rivers including Nhue and Van rivers have very bad water quality which is not acceptable for production and domestic uses. Rivers such as Vac, Chau and Day mainstream used for both irrigation and drainage are less polluted so their water sources can be supplied for production purposes. In addition, other big tributaries i.e., Thanh Ha and Hoang Long rivers which are less affected by urban domestic and industrial effluents have better quality than other rivers in the system and their water sources can be used for domestic purposes but treatment is required before using.
In Lo-Gam mainstream: Survey and measurements have been carried out at 4 points (Thanh Thuy border gate, Nam Mien, Bao Lao and Trang Thi wharf) of which 3 points are at the border controlling water sources from China territory to Viet Nam.
In Lo river at Thanh Thuy border gate water is very turbid containing sediments transported from the border, contents of suspended matters, of NH4+ and NO2- are quite high, there are also traces of micro-substance pollution such as heavy metals and toxic organic matters. Therefore it is indispensable to pursue further observations to recommend domestic water supply measures. At the moment it is not advisable to use this water source for domestic purposes.
In Mien river at the confluence with Lo river at Ha Giang town, water has been using for domestic use in Ha Giang town and at the border area. Mien river water is quite transparent at some moments of time but contents of NH4+, No2- are high that is not acceptable for domestic water supply.
In Gam river flowing from China to Viet Nam, measurement is carried out in Bao Lac district in Cao Bang province where water looks transparent but contents of NH4+, No2- are high at some moments of time. This water sources is being used for domestic purpose at the border area. Therefore it is indispensable to pursue further observations to appropriately guide people at border areas with safe treatment measures.
Water quality changes in time
Water quality changes in months and seasons: In months of dry season water sources are mainly from groundwater and regression water, agricultural surplus water is very limited so domestic and production waste water is the key water pollutant. Wastewater discharge regimes are very complicated without any fixed procedures, some enterprises even discharge waste water at night so water sampling could not catch the maximum discharging moments because of very few samples (1 time a month). As consequence, results of pollutant analysis are not typical. In the dry season, river water is seriously polluted with effluents, notably Cau river in Thai Nguyen, Thuong river in Bac Giang, Red river in Lam Thao, Viet Tri, and Nhue river in Thanh Tri, Ha Tay. Water quality is not acceptable for production and domestic uses. In months of the dry season, water pollution does not follow any timely rules but depends on discharging regimes of large urban and industrial areas. Discharging regimes are not yet surveyed or there does not exist any procedure for sewage headwork either that makes difficult to know when water quality is worst then assessment can only be made basing on field analysis.
Because of top cover wash out in the river basin together with agricultural drainage and large domestic and industrial waste disposal into rivers, water quality in rivers are not improved in early of the rainy season (surveyed in June, July) than in months of the dry season but contents of DO is even higher than of COD, and NH4‑, NO2- and coliforms are higher at some reaches as well.
Comparison of water quality in years: Water quality survey in the whole river basin was not continuously done before so there are not sufficient data to have a complete assessment of water quality changes in years. According to statistics of some parameters analyzed in 2001-2004, contents of COD and coliforms have tendency to increase and DO contents decrease in general. Preliminary assessment has been made and revealed that water quality seems to be worse by time and follows socio-economic development rules with inadequate environmental treatments whilst Law on Environment Protection is not strictly enforced. In that context, detailed assessment of water quality process by time will be made by end of 2004.
CONCLUSION
According to results of measurement, survey and analyses, industrial (from fertilizer producers, food and foodstuff processors, pulp, textile producers) and domestic waste water are the key water pollutant sources meanwhile suspended matters, organic matters, nitrate mixes and coliforms are main pollutants. Pollution of heavy metals and toxic organic matters is locally characterized, mainly found in industrial effluents. Agricultural drainage channels contain high contents of fertilizer residues at certain drainage periods. In main rivers and tributaries, pollution of heavy metals is not clear, exceptionally for upstream reaches at border where rivers water is seriously contaminated by mine exploitation activities in China. It is necessary to monitor heavy metal parameters to ensure safe utilization for domestic uses for population at the border.
In view of other sub-regions in middle and lower parts, further analysis of normal chemico-physical and micro-biological parameters is required to assess potential contamination of organic matters, nitrate mixes and microorganisms which are the main pollutants in rivers in the basin.
By Dr. To Trung Nghia - Director of Institute of Water Resources Planning
