Assessment of water quality in wells and springs across various districts of Taza City, Morocco

The quality of water resources in Taza City is strongly influenced by the rational and sustainable management of solid and liquid wastes that end up in the aquatic receiving environment without any prior treatment (Sghiouer et al. 2024). Indeed, it is regrettable that many Moroccan cities have grown considerably, the number of habitats has risen sharply, and the development of socio-economic activities and changes in lifestyles and consumption have led to an additional waste deposit increasingly, without having the time to acquire modern sanitation networks and wastewater treatment units (Nguyen et al. 2020; Axon et al. 2023).

The ‘Julien’ landfill is installed on a common site, a site chosen at random without any impact study. It is an uncontrolled dump, which receives all kinds of solid waste in its raw state (household, industrial, hospital, and agricultural). Pollutant emissions emanate permanently from the landfill, uncontrolled surface flow, or leachate infiltration in the subsoil, as well as biogas produced by the decomposition of organic matter. In addition, frequent fires and the development of smoke as well as general misuse (waste disposal, ragpickers, grazing cattle, and hygienic aspects) are still to be named, leading to significant risks and serious ecological nuisances.

An organoleptic diagnosis made it possible to note certain observations concerning the water quality of the wells and springs close to the sewage flow of Taza City: high salinity and sometimes a bad odor. A preliminary physicochemical study of most of the wells on both banks of Oued Larbaa showed the possibility of groundwater contamination by sewage infiltration (Abouabdallah et al. 2023).

Taza Province is recognized as one of the regions at a high risk of water-borne diseases, according to Mahmoud et al. (2023). The primary diseases of concern in this area are typhoid and hepatitis A, which are especially prevalent in large urban agglomerations that suffer from partial or inadequate sanitation infrastructure. The lack of comprehensive sanitation facilities leads to the contamination of water sources, making it easier for these diseases to spread among the population.

In addition, a significant contributing factor to the health risks in Taza Province is the practice of using untreated sewage for the irrigation of vegetable crops in the vicinity of Taza City. This method of irrigation introduces pathogens from the raw sewage into the food supply, posing a substantial threat to public health. When these contaminated vegetables are consumed, the risk of spreading water-borne diseases, such as typhoid and hepatitis A, increases dramatically. Ben Abbou et al. (2013) highlight that this practice not only affects those who consume the contaminated produce but also has the potential to disseminate these diseases more widely, exacerbating the public health crisis in the region.

The combination of poor sanitation and the use of raw sewage for irrigation creates a dangerous environment for the spread of water-borne diseases in Taza Province. Addressing these issues is crucial for improving the overall health and safety of the population, necessitating urgent interventions in sanitation infrastructure and agricultural practices.

The purpose of this study is to determine the extent of groundwater degradation in various districts of Taza City, Morocco. This evaluation is essential for understanding the impact of pollution originating from multiple sources, particularly landfill leachate, and streams that receive direct discharges of municipal wastewater. By analyzing water quality data from wells and springs, we aim to identify the contaminants present and their concentrations. This study will provide a comprehensive assessment of how these pollution sources affect groundwater quality, highlighting areas of concern and contributing valuable information for the development of effective water management and pollution mitigation strategies. Furthermore, the findings will help in raising public awareness and guiding policy decisions to ensure the safety and sustainability of the city's water resources.

Taza, situated in the northeastern region of Morocco, experiences a subhumid climate. Its rainfall pattern is characterized by two distinct seasons: a lengthy rainy period spanning nearly 8 months from October to May, with an average precipitation of about 510 mm, and a dry season from June to September, marked by average maximum temperatures nearing 35 °C (Ben Abbou et al. 2013).

Geographically, the Taza region is primarily located between two watersheds: the Moulouya Basin to the east and the Sebou Basin to the west (Benzougagh et al. 2020). Hydrologically, Taza city is intersected by an extensive network of watercourses, primarily consisting of the main river, Oued Larbâa, and its tributaries – Oued Taza, Oued Dfali, Oued Laghouireg, and Oued Jaouna.

From a hydrogeological perspective, Taza features two types of aquifers: a deep aquifer comprised of limestone formations and a shallow water table that gives rise to numerous water sources within the city.

The sanitation network in the city is unitary and covers almost the entire city with a total linear of 80 km. This network is made up of a group of five main collectors (Larbaâ, Taza, Rhouireg, Dfali, and Jaouna) ensuring the sanitation of most of the districts of the city. These collectors discharge the wastewater into the various points of the Oued crossing the city without any prior treatment (Abba et al. 2021).

A monthly sampling frequency was adopted during the period from May to October 2013, with a representative choice of the sampling sites.

Twenty parameters were measured, including nine (ONEP 2019) carried out in situ: temperature, conductivity, pH via a multi-parameter analyzer Type CONSORT-Model C535, turbidity with a turbidimeter Type HACH-Model 2100P, and dissolved oxygen (DO) by the Winkler titration method (ONEP 2019) and bicarbonates, calcium, and magnesium by titrimetric assay.

The sampling, transport, and storage of water samples refer to the protocol and procedures defined by the National Office for Drinking Water (Rodier & Legube 2009; ONEP 2019). The methods used in the Laboratory of Natural Resources and Environment of the Polydisciplinary Faculty of Taza are volumetry for chlorides and oxidability; molecular absorption spectrophotometry for sulfates, nitrates, nitrites, ammonium ions, and orthophosphates and flame spectrophotometry for sodium and potassium (Rodier & Legube 2009). The determination of the trace elements (Cd, Co, Cu, Fe, Ni) was carried out using induced plasma emission spectrometry at the Fez innovation center.

The samples were taken, considering no contaminating or modification of samples, in sterile bottles and transported in a cooler immediately to the laboratory where they were stored at 4 °C until the bacteriological analysis. The analysis was done within a maximum of 6 h after the sample was collected.

The study of bacteriological parameters has focused on the detection and enumeration of pollution indicators germs: coliforms, Escherichia coli (E. coli), intestinal enterococci (IE), total aerobic mesophilic flora (TAMF), anaerobic sulfate-reducing clostridium spores (ASRCS), Staphylococci and Pseudomonas. For seven germs searched, six replicates were performed on the 84 samples taken, for a total of 588 analyzes.

The samples were taken according to the Office National de l'eau potable (ONEP) sampling and analysis procedure (ONEP 2019) with a monthly frequency. Fecal coliforms (FC), total coliforms (TC), and fecal staphylococcus (FS) were counted using the indirect method of multiple tube fermentation in a lactose broth; the number was then statistically deduced using the most probable number method (Rodier & Legube 2009). The filtration is carried out on a vacuum filtration stage. Isolation and enumeration were performed in a solid medium (Table 1).

The results are presented by discussing the measured parameters, in particular the measurements carried out in situ and those carried out in the laboratory. Average results for groundwater will be cited.

Significant differences in the E. coli content were noted in the various sources: absence of E. coli. E. coli is recorded at sources S9, S10, and S13, while the minimum value is recorded at source S8 (0.85 log10/100 mL) and the maximum value at source S14 (2.99 log10/100 mL). The mean concentration is of the order of 1.68 log10/100 mL.

Fecal coliforms come exclusively from the intestines of warm-blooded animals, including humans, and their presence is the most accurate indicator of fecal contamination. Although the presence of E. coli bacteria in water indicates fecal contamination, it does not identify the precise source of fecal matter. There are several possible sources: manure, grazing, septic tanks, latrines, and other sources such as wild animals. According to our health surveys in the vicinity of the wells and sources that were the subject of our physicochemical and bacteriological analyzes, we noticed the existence of waste of all kinds in neighboring land and a direct release without any prior treatment in the streams of Taza City.

The health risk associated with the presence of total coliform bacteria is often low, with the exception of some strains of E. coli and some opportunistic bacteria that can cause serious illness in debilitated patients. Thus, Klebsiella pneumoniae can cause respiratory and genito-urinary tract infections and septicemia (Yang et al. 2022). There are, however, cases where an association between the detection of total coliforms and the appearance of water-borne epidemics has been demonstrated (Mabvouna et al. 2020; Some et al. 2021), although water without coliforms may also be responsible for gastroenterological problems (Alam & Abdullah 2022).

The presence of fecal coliforms may be an indication of the presence of enteropathogenic microorganisms (Hammad et al. 2022), such as Salmonella and Norwalk virus (Jain & Rajesh 2016; Lucero et al. 2021).

The detection of enterococci in a groundwater table or in wells must seriously suspect fecal contamination and the presence of enteropathogenic microorganisms (Lotfi et al. 2020) thus showing a correlation between the presence of enterococci and fecal coliforms in untreated drinking water. More convincingly, Chique et al. (2021) clearly demonstrated that the detection of enterococci was strongly associated with the presence of E. coli in distribution systems supplied by groundwater. As for Xiong et al. (2021), they showed an increased risk of developing gastroenteritis with a relatively small number of fecal streptococci (3–10 bacteria/100 mL). OMS (2000) (OMS 2000) suggests that groundwater should not be consumed in which Enterococci have been identified.

The content of TAMF varies slightly between the different sources; it reaches a minimum value (1.96 log10/100 mL) in the source S11 and a maximum value (3.05 log10/100 mL) in the source S14, the mean value is 2.31 log10/100 mL.

The total germs at 22 °C are bacteria of residual origin (environmental), while the total germs at 37 °C are bacteria of intestinal origin (human or animal). The high contamination of wells by total germs could be due to poor protection of wells (open pits), ignorance of basic hygiene rules, neighboring pollution (agricultural land, livestock breeding, existence of septic tanks and latrines), and the absence of liquid sanitation. The count of mesophilic aerobic germs is used as an indicator of pollution and as an indicator of treatment efficiency, in particular physical treatments such as soil filtration, which should lead either to a very great decrease in bacterial concentration compared to the entry, or even an absence of bacteria. The soil of the wells studied does not filter enough microorganisms.

It should be noted that anaerobic sulfite-reducing bacteria are often considered as controls of fecal pollution. The spore form, which is much more resistant than the vegetative forms of fecal coliforms and fecal streptococci, would thus detect old or intermittent fecal pollution.

The studied sources contain Staphylococcus contents which oscillate between 1.15 log10/100 mL as the minimum value in the source S3 and 3.13 log10/100 mL as the maximum value in the S1 source, while the mean concentration is 2.03 log10/100 mL.

The maximum value of Staphylococci in the source waters is 3,100 colony forming unit (CFU)/100 mL at source S1 (Figure 6). However, WHO standards (2000) set a ‘zero’ value for the presence of staphylococci in water intended for human consumption, given the pathogenicity of these microorganisms. The French and Canadian standards also require the total absence of these bacteria in any water intended for direct or indirect human consumption because some forms can withstand high temperatures (Rodier & Legube 2009).

For PA, is noted their absence in the S11 and S13 sources and their presence in the other sources with variability of the contents. The minimum value is recorded at source S10 (0.24 CFU/100 mL) and the maximum value is recorded at source S6 (1.56 CFU/100 mL).

The presence of PA in the studied waters represents a health risk for weakened and immunocompromised persons. As an opportunistic pathogen, this germ is responsible for a wide variety of infections: atrial, ocular, urinary, and infections of the skin or respiratory tract (Rossi et al. 2024).

The results of the germs sought in the waters of Taza City confirm the presence of an important source of pollution and that is the origin of the establishment of environments favorable to bacterial development.

The adverse effect of wastewater on groundwater quality and human health has been demonstrated by some studies (Zhang et al. 2020; Mora et al. 2022). Urban wastewater contains a lot of nutrients (macronutrients N, P, K, Ca, Mg, and micronutrients: iron) which are strongly solicited by bacterial populations (Jayakumar et al. 2021).

The ratio of fecal coliforms to IE can indicate the origin of fecal contamination (animal or human) at contaminated sources.

The results show that:

• 14.28% of the fecal contamination is of human origin,

• 42.85% of the fecal contamination is of strictly animal origin,

• 7.14% of the fecal contamination is of mixed origin, predominantly animal,

• 14.28% of fecal contamination is of mixed origin, predominantly human,

• 21.42% of the points show fecal contamination of uncertain origin. (Only the source S13 that was revealed is not affected by fecal contamination among the fourteen sources analyzed (7 and 14%).)

The majority of the studied points present a contamination by the IE whose origin could be human or animal. Human fecal flora contains more fecal coliforms than streptococci (Khan & Gupta 2020). The FC/FS ratio is greater than 1 suggesting that fecal pollution is of human nature (Bisimwa et al. 2022). According to this report, 95% of fecal streptococci (SF)-contaminated sites have fecal contamination of animal origin, whereas only source 7 with fecal contamination of human origin (FC/FS > 1).

This contamination could be caused by the infiltration or percolation of untreated sewage of domestic or agricultural origin, livestock waste, proximity to latrines and septic tanks of these water points, use of fertilizer excreta as fertilizers, or poor maintenance of water points and noncompliance with hygiene and protection rules, as evidenced by other authors (Mothapo 2020; Luong 2021).

The consumption of these waters exposes the population using them to serious health risks. The cohabitation of the other pathogens with the indicators of fecal contamination enumerated will have an impact on the health of the users because the consumption of water containing germs of fecal origin increases the number of intestinal flora already varied (Parker et al. 2020). That causes metabolic imbalances (Giordano-Kelhoffer et al. 2022). Indeed, risk of developing gastroenteritis with a limited number of SF (3–10 bacteria/100 mL) has been demonstrated (Karakan et al. 2021).

We have classified the waters of the sources analyzed according to the microbiological parameters, in order to know their conformity to be used by the consumer (drinking water, irrigation waters, and bathing waters), in compliance with the required standards.

According to the microbiological results and the compliance of the source water, no water from the analyzed sources was found to be suitable for use as drinking water, the maximum permissible value is 0/100 mL. For E. coli and IE (Bancessi et al. 2020). All the waters of the springs exceeded this value.

Source S1 is the only source whose waters are declared as non-compliant with bathing waters by presenting a 7.14% share of all the sources analyzed. However, the 92.86% were found to be suitable for bathing (NM.03.7.200-1998).

However, all the sources analyzed have waters complying with irrigation water standards with a limit value of 1,000 E. coli/100 mL (SEEE 2007).

In the course of this work, principal compound analysis (PCA) was performed on centered variables reduced using MATLAB software. The data covers all fourteen sources of Taza City. Seven variables were treated: Coliforms, E. coli, IE, TAMF, ASRCS, STAPH, and PA.

The use of principal component analysis (PCA) for the overall study of source water allows differentiation of their microbiological characteristics, a determination of their overall variations (factors) along the main axes, and especially a characterization of different poles of pollution.

Analysis of this correlation matrix shows that a good correlation has been established between coliforms, E. coli, TAMF, ASRCS, and STAPH.

TAMF, coliforms, E. coli, STAPH and ASRCS are positively correlated with the F1 axis, which accumulates 72.96% of inertia, and IE and PA is positively correlated with the F2 axis, which accumulates 16.72% of inertia (Figure 8).

The projection of the individuals on the factorial planes F1 and F2 made it possible to distinguish four different groups (Figure 8):

• - Group 1: Includes source S14, which contains very polluted and poor-quality waters in germs indicative of bacteriological pollution.

• - Group 2: It contains only the source S6 which presents water more contaminated by PA compared to the other sources.

• - Group 3: It contains only station S1, which also contains polluted water, but is relatively more contaminated by IE compared to other sources.

• - Group 4: It brings together the sources S2, S3, S4, S5, S7, S8, S9, S10, S11, S12, and S13 which present less polluted source waters in germs indicative of bacteriological pollution.

This is mainly due to the sewage infiltration of the Oued Larbaâ (wastewater collector of Taza City, the distance between this collector and the S3 does not exceed 2 m).

The mean values of the chloride content (Figure 10) evolve in parallel with those of the conductivity for all the measurement points. The chlorides could come from industrial discharges, water percolation through saline grounds (the chloride concentration upstream of Oued Larbaâ equal to 2.584, 14 mg/L), and the flow of irrigation water.

On the hydrochemical level, the waters are highly mineralized and very hard (147–325 mg/L of Ca²⁺, 8.8–112.20 mg/L of Mg²⁺, and 66.67–1,230.9 mg/L of Na⁺).

Similarly, the water quality is poor compared to the nitrate parameter since only the sources S1, S2, S3, S6, and S12 respect the Moroccan standard of 50 mg/L. The maximum mean value reached 147.9 mg/L in well S8. This result shows pollution by nutrients, the origin of which is probably related to the oxidation of nitrites by nitrification bacteria following the infiltration of wastewater.

These sources also have significant bacterial contamination which confirms the superficial flow of wastewater to the alluvial water table in the study area.

Furthermore, the findings from this observation underscore the oblique repercussions of unregulated landfill practices and wastewater disposal on groundwater pleasant. The unrestricted dumping of waste, coupled with insufficient wastewater control, has brought about a situation wherein water percolates via crevices, facilitating the infiltration of pollution into groundwater reservoirs. Particularly regarding the area of the landfill on an alluvial plain, which exacerbates the leaching of contaminants and wastewater into the groundwater, resulting in profound pollutants in the aquifer system.

The quality of water is influenced by a variety of pollutants from sources such as industrial, agricultural, and urban waste, as well as uncontrolled discharges, posing risks to human health and the environment. The concentration of DO is critical for aquatic life, with insufficient levels leading to reduced biodiversity and harmful anaerobic conditions. Nitrate (NO³⁻) and ammonium ions (NH⁴⁺) indicate pollution from nitrates and ammoniums, often associated with intensive agriculture and wastewater, affecting water potability and human health. Heavy metals such as Al³⁺, Fe, and Pb, toxic in the long term to living organisms, originate from industrial sources and ageing infrastructure. The presence of pathogens in groundwater underscores the need for rigorous monitoring and treatment to ensure the safety of drinking water against microbiological risks.

In light of those findings, pressing intervention and complete control techniques are vital to mitigate, in addition, the deterioration of groundwater pleasant withinside the observed area. Also, if no measures are taken to address these issues, the situation could worsen significantly, leading to several dire consequences. Continuous exposure to contaminated groundwater can lead to serious health problems for the local population, including gastrointestinal illnesses, neurological disorders, and increased cancer risk due to heavy metal exposure. Persistent pollution will lead to the degradation of aquatic ecosystems, affecting biodiversity and the overall health of the environment. This could disrupt local flora and fauna and harm agricultural productivity due to contaminated irrigation water. The cost of dealing with advanced-stage groundwater contamination is significantly higher than preventive measures. The local economy could suffer due to decreased agricultural yields, increased healthcare costs, and potential loss of tourism if the region becomes known for its polluted water. As the quality of groundwater deteriorates, the availability of safe drinking water will decrease, leading to water scarcity. This can cause conflicts over water resources and necessitate the import of potable water, further straining economic resources. Prolonged neglect of groundwater contamination can lead to irreversible damage to aquifer systems, making it impossible to restore them to their original state. This would have a lasting negative impact on the region's water security and ecological balance.

To prevent these outcomes, immediate action is needed. Authorities must enforce stricter regulations on waste disposal and landfill management, upgrade wastewater treatment facilities, establish monitoring systems, and initiate cleanup projects. Public education and engagement in groundwater conservation efforts are also crucial. These steps will help protect groundwater quality in Taza and similar regions, ensuring a healthier and more sustainable future.

All relevant data are included in the paper or its Supplementary Information.

The authors declare there is no conflict.