Impact of Cations (Na+, K+, Mg+2) and Anions (F-, Cl-, SO42-) Leaching from Filters Packed with Natural Zeolite and Ferric Nanoparticles for Wastewater Treatment.

Natural zeolites have been employed to adsorb contaminants in water. This study is aimed to evaluate the cation and anion leaching from the zeolite after the wastewater was passed through filters packed with a natural zeolite (heulandite-CaAl2Si7O18·6H2O). Eight treatments were evaluated in a 2 × 2 × 2 factorial treatment design. Factor A was the zeolite with two levels: 127 g and 80.4 g. Factor B was the nanoparticles with two levels: one bag (3.19 g) and two bags (6.39 g); and Factor C was the use of a magnet: with and without. There were two replications; hence, a total of 16 filters were employed. The water was obtained from a municipal wastewater treatment plant (MWTP). The cations (Na+, K+; Mg+2 and Ca+2) and anions (F-, Cl- and SO42-) were measured before (influent = IW) and after filtering (effluent = EW) three times. All treatments leached the cations Na+ (EW in a range of 175 to 232 ppm), K+ (EW in a range of 15.4 to 33.2 ppm), and Mg+2 (EW in a range of 7.40 to 10.8 ppm) but did not leach Ca+2. Likewise, the treatments leached the anions F- (EW in a range of 7.59 to 8.87 ppm), Cl- (EW in a range of 85.9 to 120 ppm), and SO42- (EW in a range of 139 to 146 ppm). We conclude that this natural zeolite leaches cations (except Ca+2) and anions in MWTP passed through filters. Therefore, its application in wastewater treatment should be considered for purposes such as agriculture and animal production and not for drinking water.

Assessing the Committed Effective Dose From 226Ra in Thermal Spring Water From San Diego De Alcala, Chihuahua, Mexico.

The oral administration of mineral-rich spring water is known as hydropinic treatment and is used to treat certain ailments. Health benefits are attributed to thermal spring water containing radioactive elements such as radium; this has popularized use of such radioactive water in various parts of the world, causing those who ingest it to increase their internal radiation dose. The goal of this study was to assess the activity concentrations of Ra present in the thermal spring waters of San Diego de Alcala, in the state of Chihuahua, Mexico, and to estimate the health risk posed to patients by the effective dose received from ingesting this water during hydropinic treatments. Water samples were taken from different areas of the San Diego de Alcala thermal springs, and pH, temperature, electrical conductivity, and total dissolved solids were measured. The Ra activity concentrations were measured with a liquid scintillation counter. The activity concentrations of Ra in sampled water varied from 125 to 452 mBq L with an average of 276 ± 40 mBq L. The committed effective dose from each of the Ra activity concentrations found in samples ranged from 9.80 × 10 to 4.0 × 10 mSv for hydropinic treatments being carried out in San Diego de Alcala thermal spring spas. Different treatments had different intake rates (200, 600, 1,000, and 1,500 mL d) and occurred over periods of 2 or 3 wk. According to the guidelines of the US Environmental Protection Agency, the maximum permissible amount of radium in drinking water is 185 mBq L; the Ra content in most of the collected samples exceeded this limit. The committed effective doses varied with Ra concentration and intake rate; none exceeded the World Health Organization's reference dose for drinking water of 0.1 mSv y, which is the maximum amount to which the population should be exposed.

Indoor Radon Gas (222Rn) Levels in Homes in Aldama, Chihuahua, Mexico and the Risk of Lung Cancer.

Radon (222Rn) is an odorless and tasteless gas that is known to cause lung cancer. The objective of this research was to quantify the levels of exposure to radon among people living in an environment rich in uranium (U). Radon concentrations were measured for 3 days in 12 homes in Aldama, Mexico. Homeowners agreed to participate in the study; hence, the sample was non-probabilistic. Radon was measured with a portable AlphaGuard Radon Monitor (Genicron Instruments GmbH), which was placed in a bedroom of each home at a height of 0.74 m. Gas levels were registered in Becquerels (Bq m−3), with readings taken every 10 min along with readings of ambient temperature (AT), air pressure (AP), and relative humidity (RH). We found that radon gas levels in Aldama exceed the maximum permissible limits (USA: 148 Bq m−3). Levels were higher at night, and were above the maximum permissible level recommended by the International Atomic Energy Agency of the United Nations (<200 Bq m−3). Most residents in the area have family histories of lung problems, but it was difficult to establish a strong correlation between 222Rn and lung cancer. Federal, state, and municipal governments should take stronger action to reduce the effects of radon gas on communities.

Removing Organic Matter and Nutrients from Pig Farm Wastewater with a Constructed Wetland System.

Pollutants from pig farms in Mexico have caused problems in many surface water reservoirs. Growing concern has driven the search for low-cost wastewater treatment solutions. The objective of this research was to evaluate the potential of an in-series constructed wetland to remove nutrients from wastewater from a pig farm. The wetland system had a horizontal flow that consisted of three cells, the first a surface water wetland, the second a sedimentation cell, and the third a subsurface flow wetland. The vegetation used was Thypa sp. and Scirpus sp. A mix of soil with red volcanic rock (10⁻30 mm diameter) and yellow sand (2⁻8 mm diameter) was used as a substrate for the vegetation. The experiments were carried out in duplicate. Water samples were collected at the inflow and outflow of the cells. Two hydraulic retention times (HRT) (5 and 10 days) and three treatments were evaluated: 400, 800, and 1200 mg·L−1 of chemical oxygen demand (COD) concentration. Data was collected in situ for temperature, pH, dissolved oxygen (DO), electrical conductivity (EC), and total dissolved solids (TDS). COD, total Kjeldahl nitrogen (TKN), ammonia nitrogen (NH3⁻N), and total phosphorous (TP) were analyzed in the laboratory. The results showed that the in-series constructed wetland is a feasible system for nutrient pollutant removal, with COD removal efficiency of 76% and 80% mg·L−1 for a 5- and 10-day HRT, respectively. The removal efficiency for TKN, NH3⁻N, and TP reached about 70% with a 5-day HRT, while a removal of 85% was obtained with a 10-day HRT. The wetland reached the maximum removal efficiency with a 10-day HRT and an inflow load of 400 mg·L−1 of organic matter. The results indicate that HRT positively affects removal efficiency of COD and TDS. On the other hand, the HRT was not the determining factor for TP removal. Treatment one, with an initial COD concentration of 400 mg·L−1, had the highest removal of the assessed pollutants, allowing for the use of water for irrigation according to Mexican regulatory standards (NOM-001). The water quality resulting from treatments two and three (T2 = 800 mg·L−1 of COD and T3 = 1200 mg·L−1 of COD) did not comply with minimal requirements for irrigation water.

Characterization of a Microbial Consortium for the Bioremoval of Polycyclic Aromatic Hydrocarbons (PAHs) in Water.

Pollution of freshwater ecosystems from polycyclic aromatic hydrocarbons (PAHs) is a global concern. The US Environmental Protection Agency (EPA) has included the PAHs pyrene, phenanthrene, and naphthalene among the 16 priority compounds of special concern for their toxicological effects. The aim of this study was to adapt and characterize a microbial consortium from ore waste with the potential to remove these three PAHs from water. This microbial consortium was exposed to the target PAHs at levels of 5, 10, 20, 50, and 100 mg L−1 for 14 days. PAH bioremoval was measured using the analytical technique of solid phase microextraction, followed by gas chromatography mass spectrometry (SPME-GC/MS). The results revealed that up to 90% of the target PAHs can be removed from water after 14 days at a concentration level of 100 mg L−1. The predominant group of microorganisms identified at the phylum taxonomic level were the Proteobacteria, while the Actinobacteria were the predominant subgroup. The removal of phenanthrene, naphthalene, and pyrene predominantly occurred in specimens of genera Stenotrophomonas, Williamsia, and Chitinophagaceae, respectively. This study demonstrates that the use of specific microorganisms is an alternative method of reducing PAH levels in water.

Developing a Water Quality Index (WQI) for an Irrigation Dam.

Pollution levels have been increasing in water ecosystems worldwide. A water quality index (WQI) is an available tool to approximate the quality of water and facilitate the work of decision-makers by grouping and analyzing numerous parameters with a single numerical classification system. The objective of this study was to develop a WQI for a dam used for irrigation of about 5000 ha of agricultural land. The dam, La Vega, is located in Teuchitlan, Jalisco, Mexico. Seven sites were selected for water sampling and samples were collected in March, June, July, September, and December 2014 in an initial effort to develop a WQI for the dam. The WQI methodology, which was recommended by the Mexican National Water Commission (CNA), was used. The parameters employed to calculate the WQI were pH, electrical conductivity (EC), dissolved oxygen (DO), total dissolved solids (TDS), total hardness (TH), alkalinity (Alk), total phosphorous (TP), Cl-, NO3, SO4, Ca, Mg, K, B, As, Cu, and Zn. No significant differences in WQI values were found among the seven sampling sites along the dam. However, seasonal differences in WQI were noted. In March and June, water quality was categorized as poor. By July and September, water quality was classified as medium to good. Quality then decreased, and by December water quality was classified as medium to poor. In conclusion, water treatment must be applied before waters from La Vega dam reservoir can be used for irrigation or other purposes. It is recommended that the water quality at La Vega dam is continually monitored for several years in order to confirm the findings of this short-term study.

Levels and Distribution of Pollutants in the Waters of an Aquatic Ecosystem in Northern Mexico.

The availability of good quality water resources is essential to ensure healthy crops and livestock. The objective of this study was to evaluate the level of pollution in Bustillos Lagoon in northern Mexico. Physical-chemical parameters like sodium, chloride, sulfate, electrical conductivity, nitrates, and the pesticide dichlorodiphenyltrichloroethane (DDT) were analyzed to determine the water quality available in the lagoon. Although DDT has been banned in several countries, it is still used for agricultural purposes in Mexico and its presence in this area had not been analyzed previously. Bustillos Lagoon was divided into three zones for the evaluation: (1) industrial; (2) communal lands; and (3) agricultural. The highest concentrations of sodium (2360 mg/L) and SAR (41 meq/L) reported in the industrial zone are values exceeding the United Nations Food and Agricultural Organization (FAO) irrigation water quality guidelines. DDT and its metabolites were detected in all of the 21 sites analyzed, in the agricultural zone ∑DDTs = 2804 ng/mL, this level is much higher than those reported for other water bodies in Mexico and around the world where DDT has been used heavily. The water in the communal zone is the least contaminated, but can only be recommended for irrigation of plants with high stress tolerance and not for crops.

An overall Water Quality Index (WQI) for a man-made aquatic reservoir in Mexico.

A Water Quality Index (WQI) is a useful statistical tool for simplifying, reporting and interpreting complex information obtained from any body of water. A simple number given by any WQI model explains the level of water contamination. The objective was to develop a WQI for the water of the Luis L. Leon dam located in the state of Chihuahua, Mexico. Monthly water samples were obtained in 2009; January 10, February 12, March 8, May 20, June 10, July 9, August 12, September 10, October 11, November 15 and December 13. Ten sampling sites were randomly selected after dividing the study area using a geographic package. In each site, two samples at the top depth of 0.20 m and 1.0 m were obtained to quantify physical-chemical parameters. The following 11 parameters were considered to calculate the WQI; pH, Electrical Conductivity (EC), Dissolved Oxygen (DO), color, turbidity, ammonia nitrogen, fluorides, chlorides, sulfates, Total Solids (TS) and phosphorous (P). The data analysis involved two steps; a single analysis for each parameter and the WQI calculation. The resulted WQI value classified the water quality according to the following ranges: <2.3 poor water; from 2.3 to 2.8 good water; and >2.8 excellent water. The results showed that the WQI values changed from low levels (WQI < 2.3) in some points during autumn time to high levels (WQI > 2.8) most of the year and the variation was due to time of sampling generally rainy season.

Coliform and metal contamination in Lago de Colina, a recreational water body in Chihuahua State, Mexico.

Lago de Colina (Colina Lake) is located about 180 km south of the city of Chihuahua (Mexico), and during the Semana Santa (Holy Week) vacation period its recreational use is high. The objective of this study was to quantify coliform and heavy metal levels in this water body before and after the Holy Week vacation period in 2010. Twenty sampling points were randomly selected and two water samples were collected at each point near the surface (0.30 m) and at 1 m depth. After the Holy Week vacation the same twenty points were sampled at the same depths. Therefore, a total 80 water samples were analyzed for fecal and total coliforms and levels of the following metals: Al, As, B, Ca, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Se, Si and Zn. It was hypothesized that domestic tourism contaminated this water body, and as a consequence, could have a negative impact on visitor health. An analysis of variance (ANOVA) study was performed for each element and its interactions considering a factorial design where factor A was sample date and factor B was sample depth. Fecal coliforms were only detected at eight sampling points in the first week, but after Holy Week, both fecal and total coliforms were detected at most sampling points. The concentrations of Al, B, Na, Ni and Se were only statistically different for factor A. The levels of Cr, Cu, K and Mg was different for both date and depth, but the dual factor interaction was not significant. The amount of Ca and Zn was statistically different due to date, depth and their interaction. No significant differences were found for any factor or the interaction for the elements As, Fe and Mn. Because of the consistent results, it is concluded that local tourism is contaminating the recreational area of Colina Lake, Chihuahua, Mexico.

Contamination of the Conchos River in Mexico: does it pose a health risk to local residents?

Presently, water contamination issues are of great concern worldwide. Mexico has not escaped this environmental problem, which negatively affects aquifers, water bodies and biodiversity; but most of all, public health. The objective was to determine the level of water contamination in six tributaries of the Conchos River and to relate their levels to human health risks. Bimonthly samples were obtained from each location during 2005 and 2006. Physical-chemical variables (temperature, pH, electrical conductivity (EC), Total solids and total nitrogen) as well as heavy metals (As, Cr, Cu, Fe, Mn, Ni, V, Zn, and Li) were determined. The statistical analysis considered yearly, monthly, and location effects, and their interactions. Temperatures differed only as a function of the sampling month (P < 0.001) and the pH was different for years (P = 0.006), months (P < 0.001) and the interaction years x months (P = 0.018). The EC was different for each location (P < 0.001), total solids did not change and total nitrogen was different for years (P < 0.001), months (P < 0.001) and the interaction years x months (P < 0.001). The As concentration was different for months (P = 0.008) and the highest concentration was detected in February samples with 0.11 mg L(-1). The Cr was different for months (P < 0.001) and the interaction years x months (P < 0.001), noting the highest value of 0.25 mg L(-1). The Cu, Fe, Mn, Va and Zn were different for years, months, and their interaction. The highest value of Cu was 2.50 mg L(-1); for Fe, it was 16.36 mg L(-1); for Mn it was 1.66 mg L(-1); V was 0.55 mg L(-1); and Zn was 0.53 mg L(-1). For Ni, there were differences for years (P = 0.030), months (P < 0.001), and locations (P = 0.050), with the highest Ni value being 0.47 mg L(-1). The Li level was the same for sampling month (P < 0.001). This information can help prevent potential health risks in the communities established along the river watershed who use this natural resource for swimming and fishing. Some of the contaminant concentrations found varied from year to year, from month to month and from location to location which necessitated a continued monitoring process to determine under which conditions the concentrations of toxic elements surpass existing norms for natural waters.

Heavy metals in water of the San Pedro River in Chihuahua, Mexico and its potential health risk.

The objective of this study was to determine the seasonal and downstream water quality variations of the San Pedro River in Chihuahua, Mexico. Water samples were collected monthly from October 2005 to August 2006 in triplicate, totaling 165 water samples. The five sampling locations were: below the Francisco I. Madero dam (LP); between Rosales and Delicias (RD); Meoqui (M); El Torreon (ET), and Julimes (LJ). The levels of As, Be, Ca, Cd, Co, Cu, Cr, Fe, Li, Mg, Mn, Mo, Ni, Pb, Sb, Se, Sr, Ti, Ta, V and Zn were measured using an Inductively Coupled Plasma- Optical Emission Spectrometry (ICP-OES) Perkin Elmer 2100. In addition, temperature, pH, electrical conductivity and total and fecal coliformes were determined. The statistical analysis considered a factorial treatment design; where factor A was the location point and factor B was sampling date. In addition, a multivariate technique looking for principal components was performed. The results indicated that some samples exceeded Mexican standards for As, Be, Ca, Cd, Co, Cr, Fe, Mn, Ni, Pb, Sb, Se, Sr and Zn. The As level must be considered for a red flag to the communities along the Rio San Pedro because both the monthly average level (0.10 mg L-1) and location (0.10 mg L-1) exceeded the Mexican and International norms. The multivariate analysis showed a predominant aggregation at the LP location, meaning that there was a predominance of As, Sr, Fe and Li. At the rest of the locations the elements did not present a tendency for aggregation. Statistics applied to sampling month showed that December, January, March and April were aggregated in a negative quadrant of component 1 indicating a predominance of V, Ni, Be, Fe and As. Overall, the results confirmed that this stretch of the San Pedro River is contaminated with heavy metals and other contaminants that might affect human health as well as the health of the ecosystem.