Current World Environment

Introduction

The saying that no water body is pure cannot be overemphasized. No matter how clean water from a natural water body appears through direct physical assessment, it is still believed that it has been affected by pollutants.^1-2 Water is vital for the existence and survival of all living organisms.³ However, this valued resource is increasingly being affected by pollution.^3-4 Pollution could be inherent from nature or through anthropogenic activities of humans.¹ Natural water bodies such as rivers, streams, lakes, and reservoirs provide domestic water for populace in most under-developed and developing nations.¹

Nche stream is one of those natural water bodies that provide water for the populace in Umunchi and its environs. Umunchi is a community in Isiala Mbano, a local government of Imo State, Nigeria. It is on record that groundwater table is far, and cannot be easily accessed within the community. Hence, efforts made by rich individuals, philanthropists and governments to sink functioning boreholes within the community have proved abortive. Due to nearness to the people and share perceived belief that natural water is not polluted, the local population especially the people of Ihuorie and Umuarusim Owerre villages found within the community, depend on this water body for domestic water supplies.

Since it has been noted that the quality of water humans take is among the factors that ensure good health,^5-6 there is need to ascertain the water quality of Nche stream and then inform the people of the community as well as appropriate authorities as the case maybe.

This study monitored the seasonal variation in the water quality of Nche stream for two seasons, with a view to ascertain the physicochemical characteristics and microbial load of the water body.

Materials and Methods

Study Area

Isiala Mbano has an average elevation of 149 meters, which is equivalent to about 489 feet. The local government area is situated within latitude 5.667Ëš (5°40´ 3.6´´) North and 7.2034Ëš (7° 12´ 22.2´´) East. Nche stream found in Umunchi, lies within the aforementioned latitude and longitude.

Water Sample Collection from Nche Stream

The water samples used for this study were collected from Nche stream between the months of April, 2014-March, 2015. The sampling was always done in the evening, when human activities on the stream were high, and on every last Saturday of each month while the sampling lasted. The sampling was done against the water current. Twelve composite samples were collected from the stream (including all the points where the local population accesses the stream), and pooled together as one.

Water sampling for physicochemical analysis was carried out with the method as described by Nwanebu.⁷ Water samples for physicochemical analysis were collected in plastic cans (Four liter capacity). Water samples for dissolved oxygen (DO) and biochemical oxygen demand (BOD) were collected using transparent amber-coloured bottles of 250 ml capacity. The methods as described by Nwanebu and Nwabueze,⁸ were used for microbiological studies and they were conveyed to the laboratory for analysis under cold condition.

Physicochemical Analysis

pH and turbidity were determined in situ with digital pH meter and turbidity meter respectively. The method as described by Ukaga and Onyeka⁹ was employed for colour determination. The methods described by Amadi et al.,¹⁰ were employed for determination of total solid (TS), total dissolved solid (TDS) and total suspended solid (TSS). The modified Wrinkler method,¹¹ was used for estimation of biochemical oxygen demand (BOD) through dissolved oxygen of the samples for different days (day zero and day five). Nitrate, phosphate, sulphate, chloride, and total alkalinity (TH) were determined using the methods described by APHA.¹¹ The method as described by Duru¹² was used for calculation of pollution index for each physicochemical characteristics and heavy metals of the studied water body.

Heavy Metal Analysis

Heavy metals in the studied water sample were determined using the methods of APHA.¹¹ Heavy metals determined were lead (Pb), zinc (Zn), iron (Fe), cadmium (Cd), manganese (Mn), mercury (Hg), chromium (Cr), and arsenic (As).

Microbial Studies

Colonial morphology, cellular morphology and biochemical tests were used for microbial studies. The methods of Cruickshank et al.,¹³ were adopted for Gram staining and starch hydrolysis test. The methods described by Cheesbrough¹⁴ were adopted for motility test, citrate utilization test, oxidase test, indole test, endospore test, urease test, and coagulase test. The methods described by Onyeagba¹⁵ were adopted for sugar fermentation test and triple sugar iron agar test. The methods adopted by Prescott et al.,¹⁶ were adopted for Voges Proskauer test, catalase test, and Methyl red test.

Results and Discussion

The monthly variations of physiochemical characteristics (Table 1) reveals that pH of Nche stream ranged from 6.41-6.87 in rainy season to 5.50-6.10 in dry season. The mean pH of 6.59 and 5.72 in rainy and dry seasons respectively were observed in the present study. The pollution index for pH was 1.01 in rainy season against 0.88 observed in dry season. Low pH of a water body could be attributed to ammonia released through the decay of proteins of dead aquatic life forms. The mean pH value of the studied stream for rainy season falls within WHO¹⁷ limit whereas that of dry season was lower than WHO limit. Consumption of acidic water according to Akubugwo and Duru¹⁸ could lead to peptic ulcer of the stomach. Total dissolved solid (TS), total dissolved solid (TDS), total suspended solid (TSS) are noted for their relationship in water sample. Total solid range of 90.05-268.51 mg/L was observed in rainy season. Total dissolved solid (TS) and total suspended solid (TDS) ranged from 28.00-120.00 mg/l and 62.05-178.04 mg/L respectively in rainy season. 160.00-148.00 mg/L, 47.90-92.01 mg/L and 54.04-82.50 mg/L were the respective observed value range for TS, TDS and TSS in dry season. Mean values for TS, TDS, and TSS for rainy season were 208.32 mg/L, 91.81 mg/L, and 116.50 mg/L respectively, while 139.88 mg/L, 72.47 mg/L, and 67.40 mg/L were the respective values for TS, TDS and TSS in dry season. The observed values for TS and TDS in both seasons were lower than their respective WHO standards of 500 mg/L and 250 mg/L respectively, while the mean values for TSS in both seasons as observed in this study were higher than its WHO standard of 50 mg/L. The pollution index of TS (0.42), TDS (0.37) and TSS (2.33) rainy season were higher than those of TS (0.28), TDS (0.29) and TSS (1.35) in dry season. Consumption of water with high solid content could lead to gastrointestinal irritation NIS.¹⁹ Conductivity for Nche stream ranged from 16.68- 68.40 µScm^-1 with a mean conductivity value of 51.71 µScm^-1 and pollution index of 1.03 in rainy season as against the 26.82- 52.79 µScm^-1 range with a mean value of 40.59 µScm^-1 and a pollution index of 0.81 observed in dry season. The relationship between conductivity and TDS as noted by APHA²⁰ and Ray et al.,²¹ was observed in the present study.

Table 1: Monthly variations in physiochemical characteristics of Nche stream between April, 2014-March, 2015.

Values are means and standard deviation of triplicate determinations.

Legend: Apr.= April; Jun=June; Jul=July; Aug.= August; Sept=September; Oct.=October; Nov.=November; Dec.=December; Jan.=January, Feb.=February; Mar.=March; BOD=Biological Oxygen Demand; TS=Total Solid; TDS=Total Dissolved Solid; TSS=Total Suspended Solid; TH=Total Hardness.

Table 2: Monthly variations of heavy metals in Nche stream between April, 2014-March, 2015

Values are means and standard deviations of triplicate determinations.

Legend: Legend: Apr.=April; Jun=June; Jul=July; Aug.= August; Sept=September; Oct.=October; Nov.=November; Dec.=December; Jan.=January, Feb.=February; Mar.=March; ND: Not Detected.

Turbidity is associated with clarity of water. Obasi et al.,²² noted that the higher the turbidity values of water, the more energy and chemicals needed at the treatment plant to treat the water. Turbidity range 3.08-7.05 mg/L with a mean value of 4.86 mg/L, and 3.00-4.40 mg/L with a mean value of 3.42 mg/L were observed in rainy and dry seasons respectively. Turbidity pollution index was 0.09 in rainy season against 0.09 of dry season. Biological oxygen demand (BOD) is noted as the standard water treatment test for the presence of organic pollutants. With the assumption that water as a medium has no bactericidal effect, the putrescible organic matter that microbial metabolism can degrade is also shown by BOD.²³ BOD of the present study ranged from 2.80-3.80 mg/L in rainy season and 3.00-4.00 mg/L in dry season. Their mean values were 3.10 mg/L for rainy seasons and 3.38 mg/L for dry season. From Moore and Moore²⁴ category of BOD values, Nche stream water could be considered as being fairly clean since the observed mean values lie between the range of 2-3 mg/L. Nitrate, phosphate and sulphate contents of a water body are used to correlate the influence of human activity on farm lands surround the water body.^{18, 20} Observed nitrate ranged from 0.60-0.84 mg/L with a mean value of 0.75 mg/L, and a pollution index of 0.02 in rainy season against the range 0.54-0.60 mg/L with a mean value of 0.56 mg/L and a pollution index of 0.01 observed in dry season. Phosphate ranged from 0.18-0.26 mg/L in rainy season to 0.17-0.23 in dry season. High sulphate range 49.00-57.30 mg/L was observed in rainy season against the range 49.30-49.60 mg/L in dry season. The observed high sulphate content of the studied water body against the values of nitrate and phosphate could be indication of predominant usage of sulphate fertilizers on farm lands surrounding the Nche stream. The observed mean values of phosphate, sulphate and nitrate in this study were lower than their respective WHO standards. According to WHO,²⁵ chloride toxicity from water has not been observed in humans except in special cases of impaired sodium chloride metabolism. Hach²⁶ noted that chloride concentration in excess could give rise to detectable taste in water. Chloride values observed in the present study ranged from 6.00- 8.11 mg/L in rainy season with a mean value of 7.60 mg/L and 8.00-8.40 mg/L in dry season with a mean value of 8.22 mg/L. Hardness in water is related to ability of water to form leather easily with soap. According to Ray et al.,²¹ water with total hardness values of less than 15 mg/L is classified as a very soft water. Nche stream water falls in this category since the mean values of total hardness of the present study did not exceed 15 mg/L in both season considered. The observed variations and mean values for total hardness were lower than WHO standard.

Monthly variations of heavy metals (Table 2) show that iron ranged from 0.60-0.65 mg/L in rainy season to 0.69-0.71 mg/L in dry seasons. Reduction in volume of water could be behind the observed increase in concentration of the metal during dry season in the present study. Zinc was between 0.09-0.13 mg/L in rainy season to 0.010- 0.013 mg/L in dry season. Manganese ranged from 0.007-0.010 mg/L in rainy season to 0.010 – 0.012 mg/L in dry season. The presence of lead with mean values of 0.009 mg/L and 0.012 mg/L for rainy and dry seasons respectively, and cadmium with mean values of 0.02 mg/L and 0.03 mg/L in rainy and dry seasons respectively in the studied water sample makes consumption of water from Nche stream questionable. Though the observed mean values of lead and cadmium metals were lower than their respective WHO standards, but the accumulation ability of the metals could be a threat to life since the local population depends heavily on water from the studied stream. Exhaust lead and chromium from cars that ply the tarred road surrounding the stream could be the source of the lead and chromium detected in this study. Mercury, chromium, and arsenic were not detected in the studied stream water.

Table 3: Bacterial isolates of Nche stream between April, 2014-March, 2015. Click here to view table

Table 4: Mould isolates from Nche stream water between April, 2014-March, 2015.