Investigation of Physico-Chemical Characteristics of Shallow Aquifer Around Dumpsites: A Case Study of Kajola, Agbowo Dumpsites, At Ibadan, Oyo State, South Western Nigeria.

Investigation of Physico-Chemical Characteristics of Shallow Aquifer Around Dumpsites: A Case Study of Kajola, Agbowo Dumpsites, At Ibadan, Oyo State, South Western Nigeria.

O.O Ikotun1and O.S Awokola2

1Department of Civil Engineering, University of Ibadan, Oyo State, Nigeria

2Department of Civil Engineering, University of Agriculture, Abeokuta, Ogun State Nigeria.

Abstract

Management of solid waste and related environmental impacts presents a challenge to both developing and developed countries. This study is to investigate the physico-chemical properties of shallow aquifer around dumpsites in Kajola, Agbowo at Ibadan. Water samples were obtained from nine randomly selected shallow aquifers around the dumpsite in January (dry season) and May (wet season). The leachate samples were also collected which was used as control. From these samples, pH and conductivity were determined using a pH-conductivity meter, while the concentrations of the heavy metals Fe, Pb and Cu were determined using atomic absorption spectrophotometer (AAS). Most of the groundwater samples are generally acidic for the dry season with mean pH value of 7.01 which is below the world health organization (WHO) and the Nigerian Standard for Drinking Water Quality (NSDWQ guidelines for potable water). Water samples from sample W3 has the highest level of DO (4.8mg/L in dry season and 4.2mg/L in wet season).During the rainy season the content of Nitrite shoot up to 1.65mg/L, high level of nitrite is discovered in well W3 showing 0.495mg/L of nitrite exceeding the permissible limit of NSQDW and WHO of 0.2mg/L. The average temperature is 29.4°C for both seasons, while well W8 during dry season has the highest temperature. The effect of excess nitrite is that it causes cyanosis, and asphyxia (blue-baby syndrome) in infants. The result of this study clearly shows a polluted environment and groundwater quality.

Keywords: Leachate, shallow aquifer, groundwater.

The discovery of pollution in groundwater sources by leachate from open dumps and landfills have been recognized for a long time. In 2006, Clark described landfill practices as the disposal of solid wastes by infilling depressions on land. The depressions into which solid wastes are often dumped include valleys, abandoned quarry sites or sometimes a selected portion within the residential and commercial areas in many urban settlements where the capacity to collect, process, dispose of, or re-use solid waste in a cost-efficient, safe manner is often limited by available technological and managerial capacities. The amount of waste generated is directly linked to the increasing population, increasing wealth and resource use. The most widely used method for disposal of municipal solid waste is landfilling, accounting for up to 95% of the total waste collected worldwide. Landfilling is also generally the most economical method of disposing of municipal solid waste. However, there are a number of environmental drawbacks associated with landfills which have aroused social and environmental attention in recent decades. Amongst the drawbacks, disposal of solid waste in landfills constitutes a considerable source of groundwater pollution. After waste is disposed off at landfills, it undergoes a number of physical, chemical and microbiological changes. Leachate is generated when water percolates through the waste layers (Kjeldsen et al. 2002). When the amount of rainfall is greater than the evaporation rate, the leachate level in the landfill increases. Leachate from a landfill can continue to pose a groundwater contamination problem for many years after the closure of the landfill.

In most developing countries such as Nigeria, several tons of garbage is left uncollected on the streets each day, acting as a feeding ground for pests that spread disease, clogging drains and creating a myriad of related health and infrastructural problems. The practice of landfill system as a method of waste disposal in many developing countries is usually far from recommended standards (Adewole, 2009). A standardized landfill system involves carefully selected location, and are usually constructed and maintained by means of engineering techniques, ensuring minimized pollution of air, water and soil and risks to man and animals. Landfilling involves placing wastes in lined pit or a mound (sanitary landfills) with appropriate means of leachate and landfill gas control. In most cases however, landfill in developing countries context is usually an unlined shallow pit,

Zurbrugg et al. (2003) referred to it as dumps which receive solid wastes in a more or less uncontrolled manner, making a very uneconomical use of the available space and that which allows free access to waste pickers, animals and flies, and often produce unpleasant and hazardous smoke from slow-burning fires.

Study Location

Ibadan the capital city of Oyo State is located approximately on Latitude 7o 22 N and Longitude 3o 58E of the Greenwich Meridian. Nevertheless, the expanse of land normally referred to as the metropolitan area lies in the portion lying between Latitudes 7o 15 and 7o 30 North of the Equator; and Longitudes 3o 45 and 4o 00 East of the Greenwich Meridian Fig 1. Dumping of refuse started in Kajola, Agbowo in Ibadan back in the early 80s after a quarry site was abandoned by road construction contractors. Their departure left behind a valley in the midst of the community without any useful contribution. The community decided to be filling the valley with waste in general not considering the environmental, health and its hazardous effect. Today, the valley is filled up and it has over flown to the surrounding houses of occupants who are very close to the location causing a major effect on the community in terms of clean environment, safe water, air pollution etc.

Figure 1: Map of NigeriaShowing Oyo State and Location of Ibadan

Materials and Methods

Sampling Sites: The samples were collected from nine shallow aquifers (hand dug wells) around the dumpsite; the leachate collected from the dumpsite (L) is used as the control for the other samples from the nine selected shallow aquifers. Details of the sampling points are in Table 1, the locations of the groundwater points were obtained with a hand held Global Positioning System (GPS, Germin 72 model) with position accuracy of less than 10 m. The choice of the sampling stations considered location of the dump site, accessibility and proximity to residential areas and the topography of the study area. Unstable parameters such as pH, temperature and conductivity were measured insitu at the point of sample collection; a thermometer was used to determine the temperature of the samples while pH211 microprocessor pH meter was used to measure the pH of the samples. The other water samples were analyzed for iron (Fe), zinc (Zn) and copper (Cu); Solute properties that have generated concerns in water development, globally (WHO, 2006), especially in terms of their toxicity. While Cu, Fe, Cr, Mg, Ca and Zn were determined with the aid of the Atomic Absorption Spectrophotometer (AAS).

In addition, Autoclave Analog Pressure Autoclave was used to sterilize the culture media prepared for cultivation of microbes for determining bacterial count and coliform count. This laboratory equipment is used to provide uniform temperature within the chambers up to and including the sterilizing temperature up to 121°C at 1 atm pressure.

Table 1: Samples location and elevation

E003°55.166'

Table 2: Physicochemical Parameters of samples of water collected in Kajola, Agbowo in Dry Season.

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Table 3: Concentration of Heavy metals on samples of water collected in Kajola, Agbowo in Dry Season.

Table 4: Bacteriological analysis on samples of water collected in Kajola, Agbowo in Dry Season.

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Table 5: Physicochemical Parameters of samples of water collected in Kajola, Agbowo in Wet Season.

Table 6: Concentration of Heavy metals on samples of water collected in Kajola, Agbowo in Wet Season.

Table 7: Bacteriological analysis on samples of water collected in Kajola, Agbowo for Wet Season.

Results and Discussion

The average temperature is 29.4°C for both seasons, while well W8 during dry season has the highest temperature. The pH results from Tables 2 and 5 indicate anaerobic or methanogenic fermentation stage of leachate. The stage is usually characterized with production of volatile fatty acid (VFAs) and high partial pressure of carbon dioxide with a pH range of 6 to 8 (Kjeidsen et al, 2002). Most of the groundwater samples are generally acidic for the dry season with mean pH value of 7.01 which is below the world health organization (WHO) and the Nigerian Standard for Drinking Water Quality (NSDWQ guidelines for potable water). Water samples from well W4 has the highest level of DO (4.8mg/L in dry season and 4.2mg/L in wet season).This value indicates a very high level of dissolved oxygen in groundwater which is below the leachate level values. It could be inferred from this observation that there is direct contamination of the aquifer by the leachate outflow. The composition of leachate varies from one part of the landfill to another thus have different pollutional effects on the environment (Tricy, 2002). The pollutional level therefore depends on its sources (sewage, detergents, industrial effluents and agricultural drainage) and volume. Traces of high turbidity shows in wells W2,W3,W5,W7 and W8 for both seasons and average leachate content of 165NTU.This values are higher than the WHO standard of 5NTU (World Health Organisation, 2006). Nitrate reduces to nitrite which can oxidize haemoglobin (Hb) to methaeglobin (metHb), thereby inhibiting the transportation of oxygen around the body (Alsabahi et al, 2009). Concentration of Total dissolved oxygen (TDS) and sulphate in groundwater sample are low and found within the specified WHO and NSDQW standards for drinking water(Table 2 and Table 5). High level of sulphate could lead to dehydration and diarrhea and children are more sensitive to it than adults. Appreciable concentration of chromium were found in Wells W4 and W9 (0.06 and 0.07mg/L) during dry season (Table 3) and in W5(0.06mg/L) during the wet season (Table 6). These values are above the WHO and NSDWQ stipulated value of 0.05mg/L of chromium in drinking water quality. Heavy dose of chromium salts even though are rapidly eliminated from human body could corrode the intestinal tract (WHO, 2004). Traces of Chlorine residue could not be found in all the groundwater samples and leachate for both seasons. The results of bacterial count for dry season ranges from 10 to 50cfu/mL and with leachate content of 80fcu/mL. The results shows an Indication of faecal contamination

of some wells in the study area. E-coli were seen in all the sampled groundwater and Leachate (Tables 4 and 7). The presence of E-coli in the groundwater is a big threat to the community because it causes Urinary tract infections, bacteraemia, meningitis, diarrhea, (one of the main cause of morbidity and mortality among children), acute renal failure and haemolytic anaemia.

Conclusion

The assessment of the groundwater quality of the shallow aquifers with respect to the general water parameters, heavy metals and micro biological determination of the water content revealed that the leachate from Kajola dumpsite within the community posed a big treat on the health issue of people living in the community. The study has also provided some relevant baseline information for accessing the public health risks, which could arise from the intake of groundwater from Kajola area,Agbowo,Ibadan.It is therefore recommended that the dumpsite condition be improved to minimize the effects on the environment or that it be relocated to another area, outside the residential area.

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