Assessment of groundwater aquifer impact from artificial lagoons and the reuse of wastewater in Qatar

Qatar is a desert where precipitation is uncommon and occurs mostly in winter. Qatar depends on desalination for drinking water and groundwater and recycled water for irrigation. There is overextraction of groundwater causing seawater intrusion. Re-use of treated wastewater (TWW) is extremely limited with only 14% of TWW being used for irrigation. This has led to the country disposing of unwanted water from various sources in artificial lagoons situated across the country where it evaporates and infiltrates the groundwater raising concerns over the possibility of environmental pollution. This is a unique situation that is limited to extremely arid countries. Research on the artificial lagoons is limited, with a noticeable knowledge gap in understanding the lagoon influence on Qatari aquifers. Accordingly, the hypothesis underpinning this research is that the quality and quantity of water in lagoons is currently having an impact on the groundwater reservoirs in Qatar. To validate this hypothesis a social survey, a hydrogeochemical survey and a microbial survey have been undertaken to establish the current situation and provide policy makers with recommendations for future lagoon management. A social survey was conducted through the distribution of online questionnaires to the public and conducting semi-structured interviews with policymakers responsible for water management in Qatar. The public had variable knowledge about the lagoons and expressed a willingness to learn more about them. Public and policymakers in Qatar agreed that there were both good and harmful consequences of the lagoons on groundwater and the environment. Policymakers' views differed, dividing into groups perceiving the lagoons as having the potential to degrade groundwater quality and those suggesting that infiltration of lagoon water would improve groundwater sources. Public opinion is important in lagoon management, thus policymakers agreed to raise awareness and incorporate public views with respect to water management in Qatar. Both public and policymakers encouraged the reuse of TWW and lagoon water and Qatar might leverage this approval to promote and extend its TWW reuse programs. A hydrogeochemical survey was conducted by sampling lagoons (n = 14) and wells (n = 54) in both the summer and winter of 2018 - 2019 (designated ‘summer’ & ‘winter’). Water, soil and plants samples from sites irrigated with well water were analysed for multiple elements by ICP-MS. Major anions were determined by ion chromatography and organic and inorganic carbon was also measured. Lagoons violated the Qatari TWW reuse standards in terms of pH, TDS, TN, SO4 2- , Mn, and Zn. Groundwater samples violated WHO and Qatar drinking and irrigation standards in terms of pH, TDS, TOC, B, Ca, Cl- , Mg, Na, SO4 2- , As, Fe, Se, Sr, Tl, and U. Spatial and temporal variation in lagoons and groundwater salinization and water/rock process were visualised to illustrate the influence of lagoon water infiltration on adjacent aquifers. Soils (collected from close to lagoons and on farms) had Ni concentrations that violated EU and FAO/Who standards. Plant samples violated EU and FAO/WHO fodder standards in terms of Cr, Cu, Mn, Mo, Ni, Pb, Se and Zn. The multivariate statistical analysis revealed similar trends in the chemical variables of soils and plants from both farms and lagoons. Contamination from water and the environment tend to be higher in plants than in soil. A microbial survey was conducted using MALDI-TOF-MS to identify species of isolated bacteria strains (MacConkey and EMB selective media) collected from lagoons (n = 9) and wells (n = 13). Both groundwaters and lagoons were found to contain levels of coliform bacteria that exceeded national and international standards. Coliform bacteria in groundwater wells were observed to be associated with nearby lagoons, implying microbial infiltration. While the majority of the literature uses E.coli as a faecal indicator for wastewater contamination of groundwater, this research determined that P.aeruginosa is a more appropriate indicator in the Qatar lagoon context. In conclusion, this study examined three distinct scientific domains pertaining to the lagoon situation in Qatar: social, chemical, and microbial, with the goal that policymakers and managers in Qatar may benefit from the findings. Additionally, this research will serve as a baseline for future research and policy development for future lagoon management decisions in Qatar