Self-purification of interval mountainous Abbas Abad River of Hamedan

1. Prelude
Surface water, especially rivers are the most important sources of water for drinking and agricultural purposes. The parameters involved in the ecosystem of the river covers a wide range and since the rate of elimination, some commonality, decrease and increase of pollutants and the factors influencing them is different, and there is in some cases, addressing all the features and parameters of water quality is not possible. In this regard, water quality parameters such as DO, BOD, COD, NH4, NO3 and PO4 in the Abbas Abad river of Hamedan were evaluated. The purpose of this study, was to simulate water quality parameters of Abbas Abad River with the QUAL2KW models and estimate the amount of pollution entering Abbas Abad River, without making environmental problems of rivers with the river enjoying self-purification capacity. Also, it is noteworthy that no research has been done using this model in Abbas Abad river, so the results can be used in developing control programs pollutant load (TMDL) for Abbas Abad river, and in the related organizations for similar applications.
2. Materials and Methods
2. 1. Study area
Abbas Abad River is 18 km long from the slopes of Mount Fakhrabad of a height 3312 meters 12 km southwest of Hamedan flowing to the north. The river in its path (between regions Ganjnameh and Abbas Abad), gets branches, and after passing Hamadan Abbas Abad village garden pours in to, in Grachqa Lands into the river (Gishin) khaku. Abbas Abad River, because is a mountainous basin, and the steep, has a swift flow. Due to the snow catchment, this river has a permanent origin.
2. 2. Research Methodology
In this study, was used QUAL2KW model to simulate DO, BOD, COD, nitrate, ammonium and phosphate and calculate parameters of self-purification capacity of the Abbas Abad River. To calibrate the model, the necessary information for the years 2012-2013 was obtained from the Environmental Protection Agency Hamadan. In order to test and validate the model, data collection was carried out in May, June and August 1394. In order to determine normal flow of the river, two patterns of the three-year river flow continuity and moving average of the river flow. And according to the 43-year period (1971-2013), the normal flow for months of the study was determined.
2. 3. Collecting data
According to the field observations and determination of the locations of wastewater disposal into the Abbas Abad River, water harvesting (dividing the water 1 and 2), lateral branches (Tarykdrh) added, were selected in 5 stations sampled on the Abbas Abad River from the Ganjnameh to the Natural History Museum (behind Faculty of agriculture), 7.43 kilometers long. These stations were sampled and analyzed in the months and required quality tests were conducted. To model, the river was divided into 16 pieces. Since the water quality of the river is influenced by flow and temperature, to determine the critical month in terms of water quality, based on 3-year moving average and Discharge River was 43-year-old took place, who was selected in August as dry months.
2. 4. Self-purification capacity and TMDL process
In this study, given Abbas Abad River plays apart to supply water to Hamedan city and another part is used as water right of farmers to irrigate gardens and agricultural land, to use drinking water and agriculture standards in the examination of self-purification capacity river, two interval were considered. First interval, the range of Ganjnameh up to water division 1, to harvest drinking water and second interval of the division of water up to the water withdrawals for agriculture in behind the School of Agriculture (water division 2) were selected. In this regard, Iran's water quality standards were used. And the standard in order to apply the water used in agriculture FAO standard was used. To determine self-purification capacity of river and total maximum of daily load, the TMDL process was used and according to the type of use (agriculture and drinking), in compliance with the respective standards safety margin was considered. For phosphate, the entering load pollutants was reduced up to standard.
3. Results
Based on these results, levels of dissolved oxygen in the range of one kilometer beginning to change is not considerable, but with the continue the path up to km 4.100, relative to the initial state, the average level A drop in 1.5 percent relatively minor exists, and then up to the end of the path was increased to 5 percent. According to the charts of ammonia and nitrate, with the increasing river discharge and dissolved oxygen, process of nitrification taken place and oxygen caused the conversion of ammonium to nitrate. This increase of nitrate, in the interval (3.500 km), an average of 15 percent, but is not the index. Also the flow increased that is combined with the relative increase oxygen, enhanced the quality of river water, and dropped amounts of BOD and COD an average of 45 percent. This also causes the status of phosphate to improve in the river.
Self-purification capacity of river: For drinking purposes, if the values of BOD, COD, NH4 and NO3 increase up to level 1, 0.3, 9.3 and 10, fold respectively, they are still acceptable In terms of drinking water standards. It should be noted that this is accordance with position and place of harvest of the river for drinking purposes (the first interval). If in future, the harvesting place of drinking water is changed, the assessment will not be valid. It should be noted that the amount of Phosphate River is always higher than the standards for drinking purposes and thus should be reduced to the initial value of 0.64. Also, for agricultural purposes, if the values of BOD, COD, NH4, NO3 and PO4 respectively up to 35, 28, 25, 46 and 40-fold increase, still will be accepted in terms of agricultural standards. As already stated, this would suit position and harvesting of water from rivers for agriculture (second period) is valid. If the relative increase parameters, examined compared to relevant standards, we find that the BOD further increases other elements, although significant difference cannot be observed between respective elements, also, there was determined the lowest level of self-purification in the first interval of COD and the second interval of NO3.
4. Conclusion and recommendations
The aim of this study was to determine assimilative capacity of the Abbas Abad River of Hamedan, in compliance with the standards and quality criteria such as parameters of DO, BOD, COD, NH4, NO3 and PO4. In this regard, QUAL2KW one-dimensional model and the measured data in May, June and August 2011, 2012 and 2015 were used. Was applied the TMDL process for to determine the self-purification capacity of the river and total maximum daily load. The results showed that due to the mountainous and steep area, re-aeration is properly done so that although the values of BOD, COD, NH4 and NO3 increase up to 1, 0.3, 9.3 and 10-fold respectively, they are acceptable in terms of standards for drinking. The river PO4 is always higher than the standards for drinking purposes and it is necessary to decrease the initial value of 0.64. For agricultural purposes, if the values of BOD, COD, NH4, NO3 and PO4, respectively, and up to 35, 28, 25, 46 and 40-fold, they will be accepted in terms of agricultural standards. Based on these results, self-purification capacity of the river in the first interval (drinking) is more than that in the second interval (agriculture). Also pattern of behavior of DO, BOD, COD, NH4, NO3 and PO4 parameters in river follows a normed probabilistic distributions, normal, Pearson, log normal, Pearson and normal respectively, and this information can help in the prediction of variability in this quality index.
Keywords: water quality, QUAL2Kw model, self-purification, Abbas Abad River