Integrated Groundwater Quality Assessment using Hydrogeochemical Characterization and Water Quality Index: A Case Study of Osun State University Campus, Southwestern Nigeria

In many parts of the world, especially in tropical regions where rivers may dry up or become polluted, people rely on water hidden deep underground. This water lives in the cracks and pores of the rocks beneath the soil. In places like southwestern Nigeria, the ground is made of ancient, hard crystalline rock known as the basement complex. Because this rock is solid and tight, water can only exist where it has been weathered into a soft, sandy layer near the surface or where deep cracks allow it to flow. Getting water from these hidden sources is vital for daily life, but the quality of that water depends on a complex conversation between the rain, the soil, and the rocks it passes through. Scientists study this interaction to understand what minerals dissolve into the water and whether human activities have added anything harmful. The goal is simple: to determine if the water coming from a well is safe to drink or if it needs treatment to protect the people who depend on it.

A team of researchers recently turned their attention to the campus of Osun State University in Osogbo, Nigeria, to investigate the groundwater that supplies the institution. They wanted to know exactly what was in the water, where it came from, and whether it was safe for students and staff to use. To do this, they collected water from ten different boreholes scattered across the university grounds, ranging from administrative buildings to research laboratories. They treated the water like a puzzle, measuring everything from its acidity and temperature to the specific minerals and bacteria it contained. By analyzing these samples, the scientists could trace the history of the water, seeing how it had interacted with the surrounding rock and whether it had been tainted by human activity.

The investigation revealed a clear story about the natural chemistry of the water. Almost every sample shared the same basic character: it was slightly acidic to neutral and dominated by calcium, magnesium, and bicarbonate. This specific mix told the researchers that the water's primary journey had been a slow chemical weathering process. As rainwater seeped through the soil, it picked up carbon dioxide and became slightly acidic, which allowed it to gently dissolve the silicate minerals in the underlying amphibolite schist rock. This natural process released calcium and magnesium into the water, creating a consistent chemical signature across the entire campus. The data showed that the water was not being heavily influenced by evaporation or by salts from the atmosphere, but was instead shaped almost entirely by its contact with the bedrock. This confirmed that the water was fresh and had been recharged recently by rainfall, rather than sitting stagnant for long periods.

However, while the natural chemistry was consistent, the water quality presented significant challenges for drinking. The most immediate problem was not the minerals, but the presence of bacteria. Every single sample tested positive for total coliform bacteria, a group of organisms that indicates the water has been contaminated by surface sources. In some cases, the levels were extremely high, far exceeding safety limits. This finding suggests that the shallow underground water is vulnerable to pollution from the surface, likely due to septic tanks, runoff, or poorly sealed wellheads. Because of this universal bacterial contamination, the water is not safe to drink directly, regardless of how clear it looks or how low its chemical pollution might be.

Beyond the bacteria, the researchers found that the water was often cloudy and rich in iron. In nine out of the ten samples, the iron concentration was higher than the recommended limit for drinking water. This iron comes naturally from the breakdown of iron-rich minerals in the rock, but when the water is pumped to the surface and exposed to air, the iron turns into a reddish-brown solid that makes the water look muddy and gives it a metallic taste. The cloudiness, or turbidity, was also too high in every sample, with some reaching levels fifty times the acceptable limit. This cloudiness is caused by tiny particles of clay and iron that remain suspended in the water. While these issues are unpleasant and can stain clothes or fixtures, they are primarily aesthetic and health concerns related to taste and appearance, rather than signs of toxic industrial pollution.

The study also looked for dangerous heavy metals like arsenic, lead, and mercury, which are often associated with industrial waste. Fortunately, the researchers found none of these toxic substances in any of the samples. This is a positive sign, indicating that the university's groundwater has not been compromised by hazardous chemical spills or industrial dumping. The only exception to the general pattern was one borehole located at the multidisciplinary research laboratory. This specific sample showed unusually high levels of dissolved solids and electrical conductivity, suggesting that chemicals from laboratory activities might have leaked into that particular well. The researchers noted this as a localized issue that requires further investigation, but it did not represent the quality of the water across the rest of the campus.

To make sense of all these findings, the team calculated a Water Quality Index, a single number that summarizes how suitable the water is for drinking. The scores varied across the campus, with some locations rated as "good" and others as "poor" or "very poor." The lower scores were driven mainly by the high levels of bacteria, iron, and cloudiness. Even the samples that scored "good" on the chemical side were still unsafe to drink because of the bacteria. The researchers concluded that the water needs treatment before it can be used. Simple steps like filtering out the iron and disinfecting the water to kill the bacteria would make it safe. They also recommended setting up protected zones around the wells to keep surface pollution away and establishing a routine schedule to test the water regularly.

Ultimately, this study provides a clear picture of the water situation at the university. The water is naturally fresh and free from toxic industrial poisons, but it is naturally high in iron and unfortunately contaminated by bacteria from the surface. The solution is not to find a new source, but to treat the existing water to remove the iron and kill the germs. By understanding exactly what is in the water and where it comes from, the university can take specific, effective steps to ensure that the water supply remains a safe and reliable resource for its community.