ANALYSIS OF MICROBIOLOGICAL CONTAMINATION IN AQUIFERS, IN THE URBAN REGION OF OBLIGADO AND HOHENAU – PARAGUAY.

calculated variations in total in Duncan test average contrast revealed statistically significant difference between wells B formation: wells A formation: sandstone, which suggests that the basalt formation wells are statistically similar to each except for well 70B that reveals a very significant statistical difference.

In Paraguay, 85% of homes have water supply from enhanced sources, 63% are delivered by a distribution system. Likewise, 79% of homes have sanitary drains and 11% are connected to an effluent treatment system (Secretaría Técnica de Planificación del Desarrollo Económico y Social, 2015), this condition hints to superficial pollution problems as well as underground water. The Capiibary Stream watershed, situated in the Department of Itapúa, Paraguay and established on the Guarani Aquifer System (SAG, in Spanish), aquifers exploited by deep wells where the presence of fecal coliform is found in 60% of sampled wells (Protección y Manejo de Aguas Subterráneas en Paraguay PAS-PY, 2012). The study calculated variations in total coliforms in groundwater watershed detected in the center of Obligado and Hohenau, the analysis of groundwater property was based on data from 59 water samples taken over a 10-year period (2006-2016) in 17 deep wells, variations of total coliforms were estimated. For the statistical processing, the analysis of variance and contrast of means (Duncan test) with margin of error 5% were performed. It was determined the variations of the overall coliforms in the study period 2006 to 2016, the presence of total coliforms topped the maximum acceptable threshold. Similarly, deep wells were detected in Obligado, whose standards extended up to 998 CFU / 100ml. Lastly, the results were contrasted with World Health Organization (WHO, 2006)  1910 Some viral and bacterial pathogens existing in human and animal waste contaminate groundwater and they are harmful to human health. In 2012, it was estimated that more than 500,000 diarrhea deaths were caused by microbiologically polluted water (Prüss-Ustün, 2014). Consistently, 50% of the world's population meets their primary requirements from contaminated groundwater at some point (Macler & Merkle, 2000).
World Health Organizations recommends that water intended for human consumption not to contain total coliforms (0 CFU/ml). Notably, 61% of all countries in the world consider this parameter as a foundation for regulations related to the provision of water for human consumption, including Canada, USA, Costa Rica, El Salvador, Bolivia, Brazil, Peru and Uruguay. Whereas 39% of the world's countries allow values higher than zero, for example, in Chile, Colombia and Ecuador, they admit up to 1 CFU/ml, as well as in Mexico, Ecuador, Honduras, Paraguay and Nicaragua the range is between 2 to 4 CFU/ml of total coliforms.
In Paraguay, according to information published by the Permanent Household Survey (EPH) 2008, 68.4% of homes had access to a household connection to drinking water, whereas the rest of the population is self-supplied basically through wells with or without pumping equipment, artesian well or additional resources. In urban areas, drinking water provision through network connection was of 79.8%, but just 14% of urban households had access to sewage system, furthermore only half of these homes had some kind of water treatment. Unfortunately, indigenous communities belonging to different ethnic groups have the lowest levels of access to public services: scarcely, 5.9% have a connection to a clean water system and just 3.3% to sewerage or other effluent treatment system. At the national level, the growth of drinking water coverage has improved substantially since the mid-1990s. While in 1995 only 39. The presence of total coliforms arises concern since the whole surface of the Capiíbary stream watershed is situated on the Guaraní Aquifer System (SAG). Typically, groundwater does not contain microbiological pollutants such as Escherichia coli and fecal as well as total coliform, excepting it has been contaminated by percolation from superficial water or sewage connections. Frequently, bacterial contamination in groundwater is due to deficient well construction, inadequate well maintenance as well as the influences of the aquifer vulnerability.
The purpose of this study was to calculate the variation of the total coliform content in Hohenau and Obligado urban areas groundwater during the period of 2006-2016. 1911

Material and Methods:-
The study was performed in two districts in the Department of Itapúa in Paraguay, the district of Obligado in the Abbeg stream watershed that is situated at the coordinates: longitude 55° 40'5.97''and latitude 27° 06' 29.60 ''; and the unnamed stream watershed in the district of Hohenau within the coordinates: longitude 55 ° 35 '58.89'' and latitude 27 ° 04' 36.81'' according to the geographical projections ( Figure 1). Wells were coded for better data management and statistical calculation thereof. Seventeen wells situated on the study area were chosen and 59 water samples were evaluated (Figures 2 and 3).
1912 Figure 2:-Position of wells in "O" Small Watershed, There were 11 wells that were coded, the nomenclature to identify them is as follow 1OC, 2OC, 3OB, 4OB, 5OB, 6OB, 7OB, 8OA, 9OA, 10OA, 11OA (letter "O" for the Abbeg stream small watershed, the numbers from 1 to 11 correspond to the order number and the letters ABC source material) and the location of the treatment plant is identified with the nomenclature. WT2 The average annual and cyclical rainfall throughout the analysis period was 1711.7 mm according to data from two meteorological stations located in the area of study, see Table 1. Rainfall data during the study period (2006 to 2016) can be seen in Figure 5, this information was gathered at the Federation of Production Cooperatives Ltda. website (FECOPROD, 2017), this station is 25 km away in straightforward line from the study area, additional source employed was METEORED from the city of Posadas, Misiones, Argentina, this station is in a straight line 48 km away from the area of study. (METEORED, 2017)  Statistical Analysis:-To identify significant differences between variables, it was performed analysis of variance as well as contrast of means, likewise, Duncan test was applied at 5% significance using the statistical program Infostat (2017p Version) (Di Rienzo, et al, 2017). It is important to mention that wells with a single data have been discarded since they produce a very marked statistical distribution.
For the analysis of the variable presence of total coliforms per well, wells with only one data have been discarded due to the fact that it generates a very marked statistical dispersion.
The outcomes were compared with levels established in the environmental guidelines related to the quality of water for human consumption in accordance with the World Health Organization (WHO, 2006) and the Official Paraguayan Standards ERSSAN (ERSSAN, 2017), to confirm the decline of water quality.

Total coliforms
Presence of total coliforms per well:- The Duncan test average contrast revealed a statistically significant difference between wells B formation: basalt, and wells A formation: sandstone, which suggests that the basalt formation wells are statistically similar to each other, except for well 70B that reveals a very significant statistical difference.
Distribution of total coliforms along the period of study:- In Figure 6, it is shown the presence of total coliforms that was detected in waters of the wells examined. The highest concentrations of total coliforms were documented in 2014, these values varied from 302 to 410 CFU/100ml, followed by 2008 when they were between 195 and 302 CFU/100ml of total coliforms.
The excessive incidence of total coliforms in 2014 and 2008 may be associated to excessive rain, these rains may influence permeation or drag sewage, it can be affirmed that in 2014 period of greatest precipitation when the study was carried out, samples were acquired in autumn (season with the highest rainfall record), also considering the year 2008, it was documented a high number of total coliforms, nonetheless that year rains were below the average during the period of study, see figure 4, being the season of highest rainfall during the year.
In 2015, the concentrations of total coliforms were lower, although it was a year of great rainfall, close to 2014 record, however in this particular year samples were taken in summer and winter (period of lower rains recording), so it is given a lower total coliforms registration. The number of total coliforms as shown in Figure 7, happens in greater quantity in the summer and autumn, in

Discussion:-
Once the historical data collected from 2006 to 20016 was analyzed, it can be affirmed that groundwater is contaminated by total coliforms, the group of coliform bacteria is applied as a general test of water quality monitoring and it has been applied all around the world to carry out studies on drinking water, aquatic systems contamination, raw wastewater sources of contamination as well as systems of wastewater treatment and recreational waters (Rose & Grimes, 2001); those reasons explain why these waters cannot be provided to the population without previous treatments, as cited by Hunter et al. (2000), who expose that bacteria, although not generally pathogenic in themselves, are indicative of potentially pathogenic microbes presence and consequently as an index of sanitary insufficiencies in the water source.
Furthermore, small watershed H wells 12HB, 13HB, 14HB, 15HB, 16HB, 17HB under study which present coliforms in a smaller percentage than the small watershed O, it diverges from the latter in two aspects a) the wells are sited in places with low population and lower population pressure as seen in figure 4, besides b) all of the wells according to their profile have their perforation in basalts, which reduces the possibility of direct entry or due to slow coliforms transfer there is no proliferation in the study area.
The finding of coliforms in wells could be due to its structural deficiency (although it was not the subject of study in this paper), as (Rodríguez, Gauna, Martínez, Acevedo, & Romero, 2012) mentioned, the finding of coliforms is possibly due to fecal matter contamination that may have come from non-jacketed wells or near surface water tables. Similarly, the presence of total coliforms in deep wells, is due to the rupture of struts or because water is extracted at a lower depth as mentioned by Jawson et. al., (1982) Conclusions:-It was statistically determined the presence of total coliforms during the period of study 2006-2016, therefore, groundwater undergoes microbiological contamination.
It can be emphasized that the most abundant precipitation during the period of study was documented in spring, summer and autumn, which is associated to the greater presence of total coliforms.

Number of total coliforms by season of the year
Total califorms CFU/100 ml