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Water quality studies of Nworie River in Owerri, Nigeria.


Nworie River is a first order stream that runs about a 5km course across Owerri metropolis in Imo State, Nigeria before emptying into another river, the Otamiri River. Its watershed is subject to intensive human and industrial activities resulting in the discharge of a wide range of pollutants. The river is used for various domestic applications by inhabitants of Owerri. When the public water supply fails, the river further serves as a source of direct drinking water, especially for the poorer segment of the city. Studies of water quality parameters are therefore necessary to determine the extent of pollution so as to monitor likely danger, not only to the human population but also to the aquatic life. A total of eleven (11) water quality parameters were investigated during the month of January 2007, which fell within the dry season in Nigeria. The parameters investigated were dissolved oxygen, carbon dioxide, pH, chloride, nitrate-nitrogen, nitrate, ammonia-nitrogen, hardness, orthophosphate, sulfide and silica. With the exception of dissolved oxygen and carbon dioxide, other chemical parameters did not exceed the water quality standards, suggesting that the river was relatively unpolluted chemically when surveyed. However, the low dissolved oxygen concentrations and high carbon dioxide concentrations strongly implicate pollution by organic wastes. Further, the study demonstrated significant longitudinal variations in the water quality parameters along the course of the river, reflecting differences in quality and quantity of pollutants at various locations. It is recommended that further studies be conducted that include the biological profile of the River.


Nworie River, a typical freshwater resource under high urban pressure, runs an approximately 5.0km course through Owerri, the capital of Imo State in southeastern Nigeria (Fig.1). The river is of enormous economic importance to inhabitants of Owerri metropolis as it serves as a water source for various domestic uses and is also a channel of sewage disposal from Owerri. The river also supports a substantial recreational and part-time fishing for youths. Some segments of the human population in Owerri use it as a direct source of drinking water, especially during failures of the public water supply.


Nworie River is potentially vulnerable to a variety of polluting influences. All through its course, there is a steady input of large quantities of detergents from laundry activities (Fig. 2). At several points, the river receives large quantities of sewage and solid wastes, especially plastic water sachets (Figs. 3 and 4). Further, when it rains, large volumes of run-off carrying agricultural and human wastes are discharged directly into the river.




It is a generally accepted view that tremendous organic loads imposed by urban sewage and other wastes constitute a major cause of pollution of natural water bodies (Hynes, 1960). There is hardly a major river today that flows into the sea unmodified. Health hazards previously unsuspected have come to light in recent decades, and 'allowable' quantities of once rare trace metals appear in modern-quantity standard lists. In view of the public apprehension of the hazards of water pollution, regular water quality monitoring of inland water bodies is highly necessary (Renn, 1970). To reveal the exact identity of pollutants, chemical analysis of a water body needs to be made. The purpose of this study was to determine the values of several chemical parameters at five sampling stations along the longitudinal course of the Nworie River; it was to determine the chemical profile of Nworie River

Material and Methods

Five sampling sites were chosen along the longitudinal stretch of the river: two sites upstream; two sites midstream; and one site downstream towards the confluence of Nworie River and Otamiri River.

Water samples were collected in the sites for two consecutive days during the month of January, 2007, which fell within the dry season in Nigeria. Water collection was done using clean plastic containers. These sample bottles were immersed below the water surface, filled to overflowing, and the cap affixed securely to eliminate the possibility of an air bubble in the container. The water samples were transported immediately to the laboratory at Imo State University, Owerri. In the laboratory the LaMotte test kits were used to perform various chemical pollution tests as directed by the manufacturer. The LaMotte test kits operated on a combination of titration and colorimetric procedures.

The chemical parameters tested were dissolved oxygen, carbon dioxide, pH, chloride, nitrate-nitrogen, nitrate, ammonia-nitrogen, hardness, orthophosphate, sulfide and silica. The test results were analyzed and compared with World Health Organization (WHO)/Environmental Protection Agency, USA (EPA) water quality standards.

Results and Discussion

Table 1 and Figures 5-6 show the results of the water analyses for the five sampling stations, namely, Upstream I, Upstream II, Midstream I, Midstream II, and Downstream compared with WHO/EPA water quality standards. Figure 5 shows the longitudinal variations of some key chemical parameter readings.


Table 1

                                  Sampling Sites

S/N     Parameters     Upstream I  Upstream II  Midstream I

1    Dissolved Oxygen     3.0          1.2          3.2
2    [CO.sub.2]          20.2         30.3         18.5
3    PH                   5.5          5.8          6.0
4    Chloride            20.5         15.0         12.0
5    Nitrate-Nitrogen     0.4          0.6          0.1
6    Nitrite              1.76         2.64         0.44
7    Ammonia-Nitrogen    <1.0         <1.0          4.0
8    Hardness (total)    28           16            8
9    Orthophosphate       0.2          0.3         <0.2
10   Sulfide             <0.3          0.3         <0.2
11   Silica               3.5          4.0          3.2

S/N  Midstream II  Downstream  WHO/EPA Standard

1        1.1           3.0         4.0-5.0
2       27.5          13.0          10.0
3        6.0           5.8         6.5-9.0
4       12.0          12.0           250
5        0.1           0.2           10
6        0.44          0.88           1
7        4.0           3.0           N/A
8        8             8             50
9       <0.2           0.2           N/A
10      <0.2           0.2           2.0
11       4.0           4.0         2-25.00+

With the exception of dissolved oxygen and carbon dioxide, the water quality parameters of Nworie River did not exceed the thresholds of WHO/ EPA water quality standards. Thus, generally speaking, the chemical pollutants in the river did not exceed water quality standards. Judging from the physical appearance of the River at various sites, it was expected that the chemical contaminants in the water would be high. This could be attributed to the fact that lotic bodies of water are in constant flow and that contaminated spots or areas eventually become clear or less turbid. However, in terms of organic wastes, this study showed that the river was under pressure and could be classified as polluted. This assertion is obvious from the dissolved oxygen and carbon dioxide concentrations and the refuse dumps in or near the banks of the water at various locations (see Figures 7--9).




Oxygen and CO2 contents are some of the practical indications of water purity. Oxygen concentrations in all the sampling studies of Nworie River were below the 5.00 ppm threshold, below which several fish species may not survive. The low oxygen concentrations were most probably a result of decay of large quantities of organic material discharged into the river. Dissolved oxygen is depleted by the decaying process. Similarly and strongly further supporting this view, the carbon dioxide concentrations were remarkably higher than thresholds in all sampling stations. High carbon dioxide concentrations usually indicate increased respiratory process, as well as increased microbial decomposition of dead organic materials. Thus a fall in dissolved oxygen concentration with a corresponding increase in carbon dioxide concentration is to be expected in situations of large inputs of organic wastes into an aquatic ecosystem. Polluted or enriched waters, will most likely, show great changes in dissolved oxygen and carbon dioxide.

Further indicators of the large inputs of organic wastes into the river were the existence of some phosphates and chlorides in the sampling stations. Most domestic wastes contain chlorides and phosphates. Contamination of domestic sewage can, in fact, be monitored by chloride assays. This is because human and animal excretions contain, on the average, 5 g Cl-1 per liter (Coles, 1979). Concentrations of phosphates and chlorides observed in this study, though lower than water quality standards, were seemingly significant.

Silica concentration, hardness and pH, all fall within range of what might be expected of a freshwater system. In rivers and lakes, silicon commonly ranges from 2-25.0 ppm, and is usually expressed as silica (Si02) in water analysis. There is a relationship between silica and biotic segment of the aquatic ecosystem, especially the diatom crop (Lund, 1964). The slight acidity of the river all through its course is not surprising. Rainwater is slightly acidic with pH of 5.5-6.0. If it reacts with soils and minerals containing weak alkaline materials, the hydroxyl ions will increase and the hydrogen ions decrease. As a result, the water may become slightly alkaline with a pH of 8.0-8.5. Thus, most natural waters will have pH values ranging from 5.0-8.5 (Renn, 1968). Nworie River is on the acidic end of this range. The catchment's area of the river is distinctly acidic, with a pH of 4.9 reported by Enwezor et al (1981). This, therefore, largely explains why the river is acidic all through.

Finally, the longitudinal variations of chemical parameters along its course provide an insight into the dynamics of anthropogenic perturbations of lotic freshwater bodies. There are spatial variations in concentrations of pollutants reflecting differences in quality and quantity of organic waste inputs at various locations in the river. For instance, the river midstream shows a higher concentration of ammonia, suggesting a steady input of fresh sewage, which was not the case upstream. The human population in Owerri metropolis is mainly concentrated around midstream of this river, hence the higher pollution rate midstream (see Table I). As the human population of Owerri grows, so also will the intensity of water pollution, perhaps up to a breaking point for the river. Survival of rivers faced with similar threats can be enhanced by deliberate measures that ensure that solid wastes and untreated sewage are not directly discharged into such river. Also attempts need be made to protect their watersheds in terms of re-forestation and discipline in construction works in their watershed.

This study was conducted during the dry season and did not include microbial analysis. It is recommended that further studies be conducted that include the microbial or biotic profile of the River as was done by Acholonu and Jenkins (2007) and also carried out during the rainy season.

It is recommended that Nworie River be dredged and with the involvement of seasoned technocrats. It may do more harm than good if improperly conducted by raking up pollutants that settled at the bottom of the river and consequently, increasing or causing the resurgence of water-borne diseases such as typhoid, cholera, dysentery and some intestinal parasitic diseases. The former river course deserves to be re-established and its esthetic beauty and cleanliness restored. Any bridge crossing the river that impedes its free flow as is presently the situation in some areas, needs to be re-constructed.


Acholonu, A.D.W. and Jenkins, T. 2007. Water quality studies on freshwater bodies in New Orleans, Louisiana one year after Hurricane Katrina. J. Miss. Acad. Sci. 52(4): 289-294.

Coles, G.A. 1979. Textbook of Limnology. Mosby Co., London, 426 pp

Enwezor, W. O., Udo E.J., and Sobulo, R.A. 1981. Fertility status and productivity of acid sands In Acid sands of southeastern Nigeria. Monograph No.l Soil Sc. Soc. Nig. pp 56-73.

Hynes, H.B.N. 1960. The biology of polluted waters. Liverpool University Press, Liverpool, 202 pp.

Lund, J.W.G. 1964. Primary production and periodicity of phytoplankton. Verh. Internal, Verein.Limnol. 15:37-56.

Renn, C. E. 1968. A study of water quality. LaMotte Chemical Products Company, Chestertown, Maryland. 46 pp.

Renn, C. E. 1970. Investigating Water problems. LaMotte Chemical Products Company, Chestertown, Maryland. 50 pp.

Peter U. Okorie (1) and Alex D.W. Acholonu (2)

(1) Department of Animal and Environmental Biology, Imo State University, P.M.B. 2000, Imo State, Nigeria

(2) Department of Biological Sciences Alcorn State University, Alcorn State, MS 39096, USA

Corresponding Author: Alex Acholonu:
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Author:Okorie, Peter U.; Acholonu, Alex D.W.
Publication:Journal of the Mississippi Academy of Sciences
Date:Oct 1, 2008
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