Groundwater quality near slaughterhouses is a critical concern for civil engineers and communities relying on borehole water for drinking and domestic use. In Uyo metropolis, Akwa Ibom State, Nigeria, slaughterhouses at Itam and Iba Oku operate in densely populated areas where residents depend on borehole water sources. Understanding how slaughterhouse activities affect groundwater quality requires systematic investigation using standard water quality assessment protocols. This article examines a research study that analysed physicochemical, heavy metal, and bacteriological parameters of borehole water around these slaughterhouses, comparing results against WHO and Nigerian standards. For engineers planning similar investigations, understanding How to Setup Borehole Layout for Site Investigation provides essential groundwork for conducting reliable water quality studies.
Study Background and Methodology
Research Area and Context
Uyo metropolis, the capital of Akwa Ibom State in southern Nigeria, sits between latitude 4°59′09.77″N and longitude 7°53′32.70″E at an altitude of 6.5 metres. The area records an annual rainfall average of 2,384.4 mm, with relative humidity ranging from 60 to 90 percent and annual temperature averaging 26.9°C. The terrain is generally flat, lying within thin beach dunes and large valleys that influence groundwater movement and potential contaminant transport.
The city has three functional slaughterhouses at Itam, Ntak Inyang, and Iba Oku. This study focused on the Itam and Iba Oku facilities, where animal wastes are commonly heaped on the ground surface. Wastes from slaughterhouses include blood, bones, undigested ingesta, urine, fats, and dissolved solids. When not properly managed, these can introduce enteric pathogens, excess nutrients, and trace heavy metals into the soil, potentially contaminating groundwater.
Sampling and Laboratory Analysis
Three water samples were collected in plastic bottles:
- Sample A from the borehole at Iba Oku slaughterhouse
- Sample B from the borehole at Itam slaughterhouse
- Sample C (control) from a borehole at Nwaniba Road, approximately 5 km from the slaughterhouses
Tap mouths were cleaned with methylated spirit before collection, and water was allowed to run for three minutes to avoid rust contamination. Containers were rinsed three times with borehole water, filled, and immediately sealed. Samples were transported to the Akwa Ibom Water Company central laboratory and preserved at 0°C.
Analysis covered three categories: physicochemical parameters (pH, turbidity, electrical conductivity, temperature, colour), heavy metals (iron, lead, cadmium, zinc, copper, chromium, aluminum, selenium, manganese), and bacteriological indicators (E. coli and total coliform). pH was measured using a HACH SENSION 3 meter, turbidity with a Hach Sension turbidimeter, conductivity and temperature with a Hach Sension 5 meter, and heavy metals using Atomic Absorption Spectrophotometric methods. Bacteriological analysis used the standard pour plate technique per NSDWQ guidelines.
Physicochemical Characteristics of Borehole Water
pH and Temperature
The pH values were 3.60 for Sample A (Iba Oku), 5.46 for Sample B (Itam), and 5.20 for the control. Both WHO and NSDWQ stipulate a pH range of 6.5 to 8.5 for drinking water, meaning all samples fell below the acceptable minimum. The low pH may be attributed to high levels of free carbon dioxide dissolving to form carbonic acid. Importantly, the slaughterhouse samples did not differ significantly from the control, indicating animal presence was not the cause. Temperature values were 21.8°C, 21.1°C, and 22.1°C, respectively, attributed mainly to atmospheric conditions.
Turbidity, Conductivity, and Colour
Turbidity was low across all samples: 1.93 NTU for the control, 0.18 NTU for Iba Oku, and 0.25 NTU for Itam, all well below the WHO limit of 5 NTU. Low turbidity indicates very low suspended solids, suggesting the water is not polluted by animal wastes. Electrical conductivity values were 482 µS/cm for Iba Oku, 173.3 µS/cm for Itam, and 235 µS/cm for the control, all below the WHO limit of 1,000 µS/cm. Colour measured 5 ILU in all samples, below the NSDWQ maximum of 15 ILU.
Physicochemical Parameters Summary
| Parameter | Control | Iba Oku | Itam | WHO Limit |
|---|---|---|---|---|
| pH | 5.20 | 3.60 | 5.46 | 6.5 – 8.5 |
| Turbidity (NTU) | 1.93 | 0.18 | 0.25 | 5 |
| Conductivity (µS/cm) | 235 | 482 | 173.3 | 1,000 |
| Colour (ILU) | 5 | 5 | 5 | 15 |
| Temperature (°C) | 22.1 | 21.8 | 22.1 | Ambient |
Heavy Metal and Bacteriological Analysis
Heavy Metal Concentrations
Heavy metals are a concern in water quality due to their toxicity even at low concentrations. The study analysed nine heavy metals across all samples. Iron was detected at 0.07 mg/L in Sample A and 0.01 mg/L in the control, well below the WHO limit of 0.3 mg/L. Manganese was detected only in Sample B at 0.01 mg/L, below the WHO guideline of 0.4 mg/L. The following metals were not detected in any sample:
- Lead (Pb) – WHO limit: 0.01 mg/L
- Cadmium (Cd) – WHO limit: 0.003 mg/L
- Zinc (Zn) – WHO limit: 3 mg/L
- Copper (Cu) – WHO limit: 1 mg/L
- Chromium (Cr) – WHO limit: 0.05 mg/L
- Aluminum (Al) – WHO limit: 0.2 mg/L
- Selenium (Se) – WHO limit: 0.01 mg/L
The absence of these metals confirms that slaughterhouse activities have no polluting effect on the borehole water. This is significant because lead, cadmium, and chromium are cumulative poisons associated with renal failure, neurological damage, and cancer.
Bacteriological Indicators
E. coli was zero in all samples, providing strong evidence of no faecal contamination. Total coliform counts were 6 cfu/100 mL for Iba Oku, 8 cfu/100 mL for Itam, and 8 cfu/100 mL for the control, all within the NSDWQ limit of 10 cfu/100 mL. The low counts and absence of E. coli confirm that animal presence at these slaughterhouses has not affected borehole water quality.
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Conclusions and Recommendations
Key Findings
The investigation yielded five key conclusions:
- All physicochemical parameters were within acceptable limits except pH, which was acidic across all samples including the control.
- Heavy metal concentrations were very low or undetectable, with iron being the highest at 0.07 mg/L, well below WHO guidelines.
- E. coli was absent in all samples, and total coliform counts were within NSDWQ limits.
- No significant difference existed between slaughterhouse borehole samples and the control 5 km away.
- Slaughterhouse activities at Itam and Iba Oku do not currently affect borehole water quality.
Continuous Monitoring and Risk Factors
Despite the favourable results, the water quality remains under threat if the current practice of dumping untreated abattoir wastes continues. Several factors could accelerate contamination:
- Accumulation over time: Cumulative organic loads may eventually exceed the natural attenuation capacity of subsurface environments.
- Seasonal variations: Increased rainfall percolation through waste heaps accelerates contaminant transport to the water table.
- Urbanisation: Growing population in Uyo means greater groundwater demand and more waste generation.
- Water table changes: Fluctuations in groundwater levels alter dilution and transport dynamics.
Recommended Preventive Measures
To sustain water quality standards, the following measures are recommended:
- Licensing and training: All slaughterhouses should be licensed, operators certified, and employees trained in waste management.
- Public awareness: Agencies should conduct campaigns on the impact of abattoir waste pollution on groundwater.
- Community participation: Public input should be included in developing abattoir management policies.
- Waste treatment infrastructure: Machinery for continuous treatment of abattoir wastes before disposal should be installed.
- Regular testing: Borehole water in slaughterhouse vicinities should be tested quarterly for physicochemical, heavy metal, and bacteriological parameters.
Proper waste treatment includes separating solid wastes (bones, hairs, undigested ingesta) from liquid wastes (blood, urine, dissolved solids) and treating each stream appropriately. Fat and oil wastes require separate handling to prevent drainage clogging and soil contamination.
In conclusion, this investigation confirms that borehole water at Itam and Iba Oku slaughterhouses is currently safe for drinking and domestic use. However, sustainable water quality depends on proper waste management. Without intervention, accumulation of untreated abattoir wastes poses a real threat to groundwater resources serving thousands of Uyo residents. Regular monitoring, public awareness, and investment in waste treatment infrastructure are essential to maintain this favourable water quality status.