Water Quality Assessment of an Untreated Effluent Impacted Urban Stream: The Bharalu Tributary of the Brahmaputra River, India

Guwahati, the lone city on the bank of the entire midstream of the Brahmaputra River, is facing acute civic problem due to severe depletion of water quality of its natural water bodies. This work is an attempt towards water quality assessment of a relatively small tributary of the Brahmaputra called the Bharalu River flowing through the city that has been transformed today into a city drainage channel. By analyzing the key physical, chemical and biological parameters for samples drawn from different locations, an assessment of the dissolved load and pollution levels at different segments in the river was made. Locations where the contaminants exceeded the permissible limits during different seasons were identified by examining spatial and temporal variations. A GIS developed for the watershed with four layers of data was used for evaluating the influence of catchment land use characteristics. BOD, DO and total phosphorus were found to be the sensitive parameters that adversely affected the water quality of Bharalu. Relationship among different parameters revealed that the causes and sources of water quality degradation in the study area were due to catchments input, anthropogenic activities and poor waste management. Elevated levels of total phosphorus, BOD and depleted DO level in the downstream were used to develop an ANN model by taking total phosphorus and BOD as inputs and dissolved oxygen as output, which indicated that an ANN based predictive tool can be utilized for monitoring water quality in the future.     

Sizing an Off-stream Reservoir with Respect to Water Availability,Water Quality,and Biological Integrity

Sizing a new reservoir is a challenging task, which normally requires simultaneously a cost-effective, risk-informed, and forward-looking decision analysis with respect to basin-wide hydrological features, environmental quality, and biological integrity. Such a sustainable planning approach takes into account the global trend to balance the needs of economic growth, ecological conservation, and environmental protection. To achieve the goal of sustainability, emphasis in this paper was placed upon the correlation of three physical, chemical, and biological indices, including the dissolved oxygen (DO), the 5-day biochemical oxygen demand (BOD₅), and the index of biotic integrity (IBI), for the optimal planning of a reservoir in a river basin. This new methodological paradigm has been employed for sizing an off-stream reservoir in the Hou-Lung River Basin, central Taiwan. The internal linkage between the water quality parameters (DO and BOD₅) and the IBI levels further enables us to formulate a special biotic integrity constraint which reflects fish community attributes to suit a relatively low-density and unspecialized freshwater fish fauna in response to the changing water quality conditions in the river basin. The tradeoffs among economic, environmental, and ecological aspects for reservoir sizing can then be based on the river flow patterns, the water demand, the water quality standards, and the anticipated biological integrity in some critical river reaches. Findings in a preliminary case study suggest that an optimal pumping scheme may be smoothly maintained on a yearly basis within a combined multicriteria and multiobjective decision-making process.     

Sensitivity Analysis and Water Quality Modeling of a Tidal River Using a Modified Streeter–Phelps Equation with HEC-RAS-Calculated Hydraulic Characteristics

A modified Streeter–Phelps equation and the Hydrological Engineering Centers River Analysis System (HEC-RAS) were combined to assess water quality of the Tan-Sui River and its tributaries. The Tan-Sui River is the main source of water supply for northern Taiwan, and the water quality of its stream is significantly affected by tides. In this study, HEC-RAS was employed to assess the impact of tides on water quality and to calculate reoxygenation coefficients. The modified Streeter–Phelps equation was used to calculate water quality in terms of contaminant degradation and reoxygenation. Biochemical oxygen demand (BOD) and ammonia nitrogen (NH₃–N), the most important identified sources of water pollution in the rivers investigated, were evaluated. Dissolved oxygen (DO) was also simulated, since it is often used as a staple of water quality. Results showed that employing HEC-RAS for hydraulic calculations improves the modified Streeter–Phelps simulation. In river sections without tidal influence, water quality was sensitive to the BOD and NH₃–N degradation constants. Downstream of Chin-Mei Creek, while the BOD degradation constant decreased by 80%, BOD and DO concentrations increased from 7.1?mg/L to 10.7?mg/L and 5.0?mg/L to 7.2?mg/L, respectively, indicating that water quality was not as sensitive to variations of the BOD degradation constant as expected. The concentrations of DO and BOD at the river mouth had a significant impact on water quality for the tidal sections of the investigated rivers due to mixing of tidal and river waters. The BOD and NH₃–N degradation constants in the tidal sections had little impact on water quality simulations. This study demonstrated the innovative combination of the modified Streeter–Phelps equation and HEC-RAS to assess the impact of tidal variation and to simulate the water quality of a tidal river when available data is rather limited.     

Chemistry of groundwater in Gulbarga district, Karnataka, India

Groundwater quality of Gulbarga District is extensively monitored for two years of study period from October 1999 to September 2001. Twenty-five different sampling stations were selected for the study purpose in the city and five selected villages in the district. Gulbarga districts lies in the northern plains of Karnataka State, covers an area of 16,244 km² and lies between 16°-11′ and 17°-19′N latitude and 76°-54′E longitude The study revealed that the water sources in the area are heavily polluted. The major water quality parameters exceeding the permissible limits during all the seasons are total hardness, calcium hardness, magnesium hardness, alkalinity and MPN (Bacterial count) and other parameters have shown distinctive variation in different stations and season. Most of these parameters are correlated with one another. Statistical analysis of the data is presented.     

Application of Water Quality Indices and Dissolved Oxygen as Indicators for River Water Classification and Urban Impact Assessment

The usefulness of water quality indices, as the indicators of water pollution, for assessment of spatial-temporal changes and classification of river water qualities was verified. Four water quality indices were investigated: WQI (considering 18 water quality parameters), WQI(min) and WQI(m) (considering five water quality parameters: temperature, pH, DO, EC and TSS) and WQI(DO) (considering a single parameter, DO). The water quality indices WQI(min), WQI(m) and WQI(DO) could be of particular interest for the developing countries because of the minimum analytical cost involved. As a case study, water quality indices were used to evaluate spatial and temporal changes of the water quality in the Bagmati river basin (Nepal) for the study period 1999-2003. The results allowed us to determine the serious negative effects of the city urban activity on the river water quality. In the studied section of the river, the water quality index (WQI) was 71 units (classified as good) at the entry station and 47.6 units (classified as bad) at the outlet station. For the studied period, a significant decrease in water quality (mean WQI decrease = 11.6%, p = 0.042) was observed in the rural areas. A comparative analysis revealed that the urban water quality was significantly bad as compared with rural. The analysis enabled to classify the water quality stations into three groups: good water quality, medium water quality and bad water quality. WQI(min) resulted in overestimation of the water quality but with similar trend as with WQI and is useful for the periodic routine monitoring program. The correlation of WQI with WQI(min) and DO resulted two new indices WQI(m) and WQI(DO), respectively. The classification of waters based on WQI(m) and WQI(DO) coincided in 90 and 93% of the samples, respectively.     

Spatial–temporal variation and comparative assessment of water qualities of urban river system: a case study of the river Bagmati (Nepal)

The study presents the assessment of variation of water qualities, classification of monitoring networks and detection of pollution sources along the Bagmati River and its tributaries in the Kathmandu valley of Nepal. Seventeen stations, monitored for 23 physical and chemical parameters in pre-monsoon, monsoon, post-monsoon and winter seasons, during the period 1999-2003, were selected for the purpose of this study. The study revealed that the upstream river water qualities in the rural areas were increasingly affected from human sewage and chemical fertilizers. In downstream urban areas, the river was heavily polluted with untreated municipal sewage. The contribution of industries to pollute the river was minimal. The higher ratio of COD to BOD (3.74 in the rural and 2.06 in the urban) confirmed the increased industrial activities in the rural areas. An increasing trend of nitrate was found in the rural areas. In the urban areas, increasing trend of phosphorus was detected. The water quality measurement in the study period showed that DO was below 4 mg/l and BOD, COD, TIN, TP and TSS above 39.1, 59.2, 10.1, 0.84 and 199 mg/l, respectively, in the urban areas. In the rural areas, DO was above 6.2 mg/l and BOD, COD, TIN, TP and TSS below 15.9, 31, 5.24, 0.41 and 134.5 mg/l, respectively. The analysis for data from 1988 to 2003 at a key station in the river revealed that BOD was increasing at a rate of 1.8 mg/l in the Bagmati River. A comparative study for the water quality variables in the urban areas showed that the main river and its tributaries were equally polluted. The other comparison showed the urban water qualities were significantly poor as compared with rural. The cluster analysis detected three distinct monitoring groups: (1) low water pollution region, (2) medium water pollution region, (3) heavy water pollution region. For rapid assessment of water qualities using the representative sites could serve to optimize cost and time without loosing any significance of the outcome. The factor analysis revealed distinct groups of sources and pollutions (organics, nutrients, solutes and physicochemical).     

Water Quality Assessment and Modeling of an Effluent-Dominated Stream, the Notwane River, Botswana

In an effort to assess current and future water quality of the only perennial river in southeastern Botswana, this study presents water quality monitoring and modeling results for the effluent-dependent Notwane River. The water quality along the Notwane River, pre- and post-implementation of secondary wastewater treatment, was compared and results demonstrated that water quality improved after the new wastewater treatment plant (WWTP) went online. However, stream standards for chemical oxygen demand, total dissolved phosphorous, and fecal coliform were exceeded in most locations and the critical dissolved oxygen (DO) reached concentrations of less than 4 mg L⁻¹. High dissolved P concentrations and intense macrophyte growth at the impounding ponds and at sites within 30 km of the effluent waste stream confluence suggest that eutrophication was a function of P release from the ponds. Results of DO modeling demonstrated that an unpolluted inflow at approximately 10 km downstream of the confluence was responsible for raising DO concentrations by 2.3 mg L⁻¹, while SOD was responsible for a decline in DO concentrations of 1.4 mg L⁻¹ at 6 km downstream of the confluence. Simulations also showed higher DO concentrations during winter months, when water temperatures were lower. Simulations, in which the distributed biochemical oxygen demand (BOD) loading from cattle excrement was decreased, produced nominal increases in DO concentrations. An increase in WWTP BOD loadings to projected 2020 values resulted in a 1.3 mg L⁻¹ decrease in the critical DO concentration. Furthermore, a decrease in treatment plant efficiency, from 94% to 70% BOD removal, produced critical DO concentrations and anoxia along much of the modeled reach. This has significant implications for Gaborone, especially if decreased WWTP efficiency occurs as a result of the expected future increase in pollutant loadings.     

Monitoring of the physical parameters and evaluation of the chemical composition of river and groundwater in Calabar (Southeastern Nigeria)

A 12-month study was carried to assess the seasonal and tidal effects on the physical parameters of river and groundwater, which constitute the major potable water sources in Calabar (Nigeria). The study also included an evaluation of the chemical composition of the different water bodies and their relationship. The results show that there was a significant seasonal effect on dissolved oxygen (DO) and nitrate in groundwater on one hand, and on temperature, redox potential (Eh), and DO in river water on the other. Also, a significant tidal influence exists on DO in both river-and groundwater. Comparison between groundwater and river water show statistically significant difference in EC, TDS, Eh, DO, Na, Cl and NO(3). The significant differences in EC, TDS, Na and Cl are due to tidal flushing. The difference in Eh is due to geology of the area while, NO(3) is as a result of anthropogenic pollution. The concentrations of ions in the river and groundwater for the different seasons and tidal cycles show an inverse relationship, while the river water is generally more concentrated than the groundwater. Using a binary mixing model, estimates show that the degree of mixing of river water and groundwater is low, with values of between 1.93% and 2.76% respectively, in the western and eastern parts of the study area. The study concludes that tidal flushing, anthropogenic effects and oxygen supply during recharge contribute to the shaping of water chemistry in the area.     

Qualitative evaluation of Kanhan river and its tributaries flowing over central Indian plateau

Water quality evaluation of Kanhan river and its tributaries viz. Pench and Nag rivers was carried out in order to assess the qualitative changes and possibility of point and non-point pollution loads in these rivers for the post monsoon and summer seasons. pH, turbidity, conductivity, total alkalinity and total hardness were found in the range 7.18.7, 0.835 (NTU), 227970 (microScm(-1)), 7.18.7, 158486 (mg/L) and 142246 (mg/L), respectively. Ca, Mg, Na and K were in the range 2462, 1328, 15183 and 333 mg/L, respectively. The respective ranges of Cl, SO(4), NO(3) and PO(4) were observed between 19102, 823, 332 and 0.11.4 mg/L. DO and COD in the rivers ranged between nil to 8.5 and 7172 mg/L, respectively. Absence of DO and higher COD in Nag river is due to its sewage content from Nagpur city. Nag river showed higher bacterial counts than Kanhan and Pench rivers. The temporal and spatial variability in the river water quality may be attributed to catchment characteristics, agricultural and urban activities in catchment and on the bank of the river. The values of RSC, ESP and SAR indicated that the water of Kanhan and Pench rivers are suitable, whereas that of Nag river is unsuitable for irrigation purpose.     

Defining chemical status of a temporary Mediterranean River

Although the majority of rivers and streams in the Mediterranean area are temporary, no particular attention is being paid for such systems in the Water Framework Directive (WFD). A typical temporal Mediterranean river, draining an intensively cultivated basin, was assessed for its chemical status. Elevated concentrations of nitrates and salts in river water as well as nutrients and heavy metals in river sediments have been attributed to agricultural land uses and practices and point sources of organic pollution. A scheme for the classification of the river's chemical status (within the ecological quality classification procedure) was applied by combining pollution parameters in groups according to related pressures. In light of the temporal hydrological regime and anthropogenic impacts, sediment chemical quality elements were considered, in addition to hydrochemical ones. Despite the extensive agricultural activities in the basin, the majority of the sites examined showed a good quality and only three of them were classified as moderate. For the classification of the chemical quality of temporary water bodies, there is a need to develop ecologically relevant salinity and sediment quality standards.     

Evaluation of water quality index for drinking purposes for river Netravathi, Mangalore, South India

An attempt has been made to develop water quality index (WQI), using six water quality parameters Dissolved oxygen (DO), Biochemical oxygen Demand (BOD), Most Probable Number (MPN), Turbidity, Total Dissolved Solids (TDS) and pH measured at eight different stations along the river basin. Rating curves were drawn based on the tolerance limits of inland waters and health point of view. Bhargava WQI method and Harmonic Mean WQI method were used to find overall WQI along the stretch of the river basin. Five point rating scale was used to classify water quality in each of the study areas. It was found that the water quality of Netravathi varied from Excellent to Marginal range by Bhargava WQI method and Excellent to Poor range by Harmonic Mean WQI method. It was observed that the impact of human activity was severe on most of the parameters. The MPN values exceeded the tolerable limits at almost all the stations. It was observed that the main cause of deterioration in water quality was due to the lack of proper sanitation, unprotected river sites and high anthropogenic activities.     

Contamination of Oxygen-Consuming Organics in the Yellow River of China

Contamination of oxygen-consuming organics (OCOs) was one of the most serious problems in the Yellow River of China. This study was conducted to analyze monitoring of the data on OCOs contamination for the river in 1980 and during 1992–1999 as well as examining the effect of suspended solids (SS) on chemical oxygen demand (COD_Mn) and biochemical oxygen demand (BOD₅) of river water. Several significant results have arisen from the study. First, COD_Mn and BOD₅ of the river water showed an increasing trend from the upper to the lower reaches of the mainstream. BOD₅ values of river water in 1992 were significantly higher than those in 1980 and showed an increasing trend during 1992–1999. Second, OCOs in river water of the mainstream was attributed mainly to point sources; the ratio of point to non-point sources of BOD₅ was about 2.81. The load from point sources showed an increasing trend during 1992–1998. In contrast, the load from non-point sources manifested a decreasing trend during this period; this was caused by the decreasing trend of SS content in river water. The total load of BOD₅ from point and non-point sources displayed an increasing trend during 1992–1998. Third, as the humic substances in SS can hardly be biologically oxidized in natural conditions but can be oxidized by chemical oxidants such as potassium permanganate, COD_Mn was not suitable for being regarded as a parameter reflecting the pollution degree of OCOs in river water with a high SS content.     

Ecological study of river Suswa: modeling DO and BOD

In this paper limnological status of river Suswa was observed for a period of two years. A water quality Beck modified Khanna Bhutiani model (BMKB model) was developed to calculate DO (dissolved Oxygen) and BOD (biochemical oxygen demand). The model was developed to calculate DO and BOD by using DO/BOD of same place and upstream in previous season which results in Single output. This model gives the seasonal value on the basis of previously taken upstream and downstream observations/concentrations of DO and BOD. The model was calibrated and verified for the water quality data (Physico-chemical data) of samples collected from river Suswa in different seasons. The model gave good agreement between data observed by it and the data observed manually, thus substantiating the validity of the model. Only minor differences were observed in physical, chemical and heavy metals of all the four sampling stations during the course of study.     

Water Quality Changes in Chini Lake, Pahang, West Malaysia

A study of the water quality changes of Chini Lake was conducted for 12 months, which began in May 2004 and ended in April 2005. Fifteen sampling stations were selected representing the open water body in the lake. A total of 14 water quality parameters were measured and Malaysian Department of Environment Water Quality Index (DOE-WQI) was calculated and classified according to the Interim National Water Quality Standard, Malaysia (INWQS). The physical and chemical variables were temperature, dissolved oxygen (DO), conductivity, pH, total dissolved solid (TDS), turbidity, chlorophyll-a, biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solid (TSS), ammonia-N, nitrate, phosphate and sulphate. Results show that base on Malaysian WQI, the water in Chini Lake is classified as class II, which is suitable for recreational activities and allows body contact. With respect to the Interim National Water Quality Standard (INWQS), temperature was within the normal range, conductivity, TSS, nitrate, sulphate and TDS are categorized under class I. Parameters for DO, pH, turbidity, BOD, COD and ammonia-N are categorized under class II. Comparison with eutrophic status indicates that chlorophyll-a concentration in the lake was in mesotrophic condition. In general water quality in Chini Lake varied temporally and spatially, and the most affected water quality parameters were TSS, turbidity, chlorophyll-a, sulphate, DO, ammonia-N, pH and conductivity.     

成都市河流生态健康评价

研究以成都市域内河流为研究对象,通过采样分析得到水质、生境状况、浮游藻类、底栖动物等相关指标,利用综合指标体系法,评价成都市域内河流生态系统健康状况,并结合成都市人口、土地利用、地区生产总值等因素分析人类活动与河流生态健康的关系。结果表明:成都市河流浮游藻类以硅藻和绿藻为主,部分中下游采样点出现以蓝藻为主的情况;底栖动物以指示有机污染的颤蚓科出现的频率最高,约48%的采样点以颤蚓科为优势种;约74%的河流生态健康状况为"差"或"很差",河流生态健康状况整体呈现中上游优于下游、城市周边优于市区的特征;人口密度、人类活动用地比例与河流中氨氮呈显著正相关,人类活动会显著影响河流生态系统健康。     

Cytotoxicity and genotoxicity of Guaribas river water (Piauí, Brazil), influenced by anthropogenic action

In general, tropical rivers have a great impact on human activities. Bioaccumulation of toxins is a worldwide problem nowadays and has been, historically, overlooked by the supervisory authorities. This study evaluated cytogenotoxic effects of Guaribas river (a Brazilian river) water during dry and rainy seasons of 2014 by using the Allium cepa test system. The toxicogenetic variables, including root growth, mitotic index, and chromosomal aberrations, were analyzed in meristematic cells of A. cepa exposed to water samples taken from the up-, within, and downstream of the city Picos (state: Piauí). The physical-chemical parameters were also analyzed to explain water quality and possible anthropogenic action. Additionally, the presence of heavy metals was also analyzed to explain water quality and possible damaging effects on eukaryotic cells. The results suggest that the river water exerted cytotoxic, mutagenic, and genotoxic effects, regardless of the seasons. In addition, Guaribas river presented physico-chemical values outside the Brazilian laws, which can be a characteristic of human pollution (domestic sewage, industrial, and local agriculture). The genetic damage was positively correlated with higher levels of heavy metals. The pollution of the Guaribas river water may link to the chemical contamination, including the action of heavy metals and their impacts on genetic instability in the aquatic ecosystem. In conclusion, necessary steps should be taken into account for further toxicogenetic studies of the Guaribas river water, as it has an influence in human health of the same region of Brazil.     

Water quality assessment, by statistical analysis, on rural and urban areas of Chocancharava River (Río Cuarto), Córdoba, Argentina

Water quality has degraded dramatically in the Chocancharava River (Río Cuarto, Córdoba, Argentina) due to point and non-point sources. This paper aims to assess spatial and temporal variations of physical and chemical parameters of the river. Six sampling sites and six sampling campaigns were developed. During the period 2007–2008, wet and dry seasons were included. A statistical analysis was carried out with 23 physical and chemical variables. Then, a new statistical analysis was carried out including the Riparian Corridors Quality Index and the physical and chemical variables (24 variables). Considering a multivariate system, analysis of variance, principal component analysis and cluster analysis were used. From the statistical analysis, the river was divided into two zones with different degrees of contamination. The most polluted zone is due to pollution inputs of urban, industrial and agricultural sources. This area showed a remarkable deterioration in water quality, mainly due to wastewater discharges. According to Riparian Quality, better results were found in sections of poor water quality, due to the fact that the river bank forest was less degraded downstream of the sewage discharge.     

Application of QUAL2Kw for water quality modeling and dissolved oxygen control in the river Bagmati

A stream water quality model, QUAL2Kw, was calibrated and validated for the river Bagmati of Nepal. The model represented the field data quite well with some exceptions. The influences of various water quality management strategies have on DO concentrations were examined considering: (i) pollution loads modification; (ii) flow augmentation; (iii) local oxygenation. The study showed the local oxygenation is effective in raising DO levels. The combination of wastewater modification, flow augmentation and local oxygenation is necessary to ensure minimum DO concentrations. This reasonable modeling guarantees the use of QUAL2Kw for future river water quality policy options.     

Evaluation of groundwater quality and its suitability for drinking and agricultural use in Thanjavur city, Tamil Nadu, India

As groundwater is a vital source of water for domestic and agricultural activities in Thanjavur city due to lack of surface water resources, groundwater quality and its suitability for drinking and agricultural usage were evaluated. In this study, 102 groundwater samples were collected from dug wells and bore wells during March 2008 and analyzed for pH, electrical conductivity, temperature, major ions, and nitrate. Results suggest that, in 90% of groundwater samples, sodium and chloride are predominant cation and anion, respectively, and NaCl and CaMgCl are major water types in the study area. The groundwater quality in the study site is impaired by surface contamination sources, mineral dissolution, ion exchange, and evaporation. Nitrate, chloride, and sulfate concentrations strongly express the impact of surface contamination sources such as agricultural and domestic activities, on groundwater quality, and 13% of samples have elevated nitrate content (>45 mg/l as NO₃). PHREEQC code and Gibbs plots were employed to evaluate the contribution of mineral dissolution and suggest that mineral dissolution, especially carbonate minerals, regulates water chemistry. Groundwater suitability for drinking usage was evaluated by the World Health Organization and Indian standards and suggests that 34% of samples are not suitable for drinking. Integrated groundwater suitability map for drinking purposes was created using drinking water standards based on a concept that if the groundwater sample exceeds any one of the standards, it is not suitable for drinking. This map illustrates that wells in zones 1, 2, 3, and 4 are not fit for drinking purpose. Likewise, irrigational suitability of groundwater in the study region was evaluated, and results suggest that 20% samples are not fit for irrigation. Groundwater suitability map for irrigation was also produced based on salinity and sodium hazards and denotes that wells mostly situated in zones 2 and 3 are not suitable for irrigation. Both integrated suitability maps for drinking and irrigation usage provide overall scenario about the groundwater quality in the study area. Finally, the study concluded that groundwater quality is impaired by man-made activities, and proper management plan is necessary to protect valuable groundwater resources in Thanjavur city.     

Allium cepa L. as a bioindicator to measure cytotoxicity of surface water of the Quatorze River,located in Francisco Beltrão,Paraná, Brazil

Due to an increase in water consumption in the industrial sector and within the Brazilian population, surface water that receives wastewater from industries, domestic sewage, agricultural industries, and sewage treatment stations can pollute water bodies when not properly treated. The water quality has been linked to catchment characteristics and intensity of agricultural activities. Thus, the aim of this study was to monitor the cytotoxic potential of the water of the Quatorze River, located in the town of Francisco Beltrão, Paraná, Brazil, along its route in the rural area, using the root meristematic cells of Allium cepa L. as a bioindicator. The results showed that the water at points 2, 3, and 4 were not cytotoxic because the rates of A. cepa cell division were unaltered. Point 1 had presented a mitotic index that was statistically larger than the negative control, indicating that this water contained substances with mitogenic capacity, as demonstrated by elevated values in chemical oxygen demand (COD) and biochemical oxygen demand (BOD). However, the mitotic index values decreased along the route of the river (point 1 to point 4), possibly indicating a mechanism of self-purification, despite having received other sources of pollution. Thus, the results of this study show that the water of the Quatorze River should undergo periodic environmental monitoring at different times of the year, including cytotoxicity analysis, to evaluate the principal sources of contamination to maintain the quality of the river water and, consequently, to maintain human health and equilibrium of the entire ecosystem.