Microbial Assay of Otamiri River and Its Sediments in Parts of Owerri

The aim of the study was to analyse and identify microbial constituents in the water and sediment samples with comparison of the River to World Health Organisation (WHO, 2011) standard for drinking water and Federal Ministry of Environment (FME, 2006) and their public health implications with respect to water quality. The microbial assay of Otamiri River was investigated using Standard plate count. The result indicates that microbial constituents of Otamiri river obtained at five strategic gauge stations designated SSWS 1 (Eg-bu), SSWS 2 (Timber Market), SSWS 3 (FUTO), DOWNSTREAM (Mbirichi) and CONTROL POINT with mean Total coliform Count of 3.0 × 10 2 , 3.0 × 10 3 , 4.1 × 10 3 and 1.0 × 10 3 cfu/100ml with control point value of 0.5 × 10 3 respectively. The mean Total Bacteria Count was 3.0 × 10 4 , 2.1 × 10 3 , 1.1 × 10 3 and 0.8 × 10 3 cfu/100ml respectively with control point value of 0.2 × 10 3 while the mean values for Total E. coli Count were 1.1 × 10 2 , 3.0 × 10 2 , 4 × 10 3 and 2.0 × 10 Organisation (WHO, 2011) Standard for drinking water and Federal Ministry of Environment (FME) 2006 standard for soil and thus constitute a threat to the River; these are attributed to waste dumps and anthropogenic activities around the five stations. The presence of bacteria in water can cause cholera, hepatitis, dysentery and typhoid. The microbial constituents can be reduced by chlorination.


Introduction
Water pollution is a major problem globally. It has been suggested that it is the leading worldwide cause of deaths and diseases and that it accounts for the deaths of more than 14,000 people daily (Mgbemena et al., 2012). Water pollution describes the presence of materials in water that interferes unreasonably with one or more beneficial uses of water (Akhionbare, 2009). Water pollution, especially surface water, can be caused by mining, recreational and agricultural activities. Agents of surface water pollution include bacteria, viruses and other substances present in such concentration or numbers to impair the quality of the water rendering it less suitable or unsuitable for its intended use and presenting a hazard to man or to his environment (Egereonu & Ibe, 1999;Egereonu et al., 2012).
The Otamiri River is a major fresh surface water resource of South-eastern Nigeria. The river takes its name from "Otamiri", a deity who owns all the water that is called by its name, and who is often the dominating god of Mban houses (Ihenyen & Aghimien, 2002;Fagorite et al., 2019). It is located on latitude 5˚23'N and 5˚30'N, and Longitude 6˚58'E and 7˚04'E ( Figure 1). The river runs south from Egbu (its source) pass Owerri and through Nekede, Ihiagwa, Eziobodo, Obowuumuisu, Mgbirichi and Umuagwo (all in Imo state) to Ozuzu in Etche Local Government Area of Rivers state where it has a confluence with Oramirukwa River; both rivers flow from there into the Atlantic Ocean (Fagorite et al., 2019). According to Fagorite et al. (2019), Otamiri River is used for domestic, industrial and agricultural activities. The stream sediments on the river are used for various construction purposes. The quality of the river is exposed to threat from indiscriminate waste disposal, fishing, oil and natural gas activities to mention a few. Therefore, constant monitoring of the quality of surface water cannot be overstressed especially now that increase in population has resulted in generation of more waste thus exposing the water to more pollutants (Fagorite et al., 2019).
The aim of the study was to analyse and identify microbial constituents in the  Environment (FME, 2006) of the River and their public health implications. Recent studies on Otamiri River have been basically limited to just the water quality without relation with the sediment. Such study includes that of (Adieze et al., 2016), in which the effect of untreated sewage effluents on the water quality was investigated. Another study in India by Kora et al. (2017), on the water quality both physico-chemically and bacteriological parameters of Hussain Sagar lake. But the present study identified and analysed both water samples and sediment samples for microbial constituents in Otamiri River.

Geology and Hydrogeology of the Study Area
The geology of the area shows that it is underlain by the Benin Formation ( Figure 1) which is an extensive stratigraphic unit in Southern Nigeria. The Benin Formation has variable thickness. It is underlain on land by the Oligocene-Miocene Ogwashi-Asaba Formation; on the subsurface by the petroleum bearing Agbada and Akata Formations (Ananaba et al., 1993). The Benin sands and sandstones are mainly deposits of continental upper deltaic plain environment. It is predominantly sandy with few shale intercalations becoming more abundant towards the base. The sands and sandstone are coarse grained pebbles, sub angular to well rounded and whitish or yellowish in colour probably because of limonite coating and bears lignite streaks and wood fragments (Ananaba et al., 1993). The sands may represent point bar deposits, channel fills or natural levees whereas the shales may be interpreted as back swamp deposits and oxbow fills. The thickness of the formation is variable and may be more than 1800 m.

Sample Collection
Eleven water samples were obtained along the stretch of the Otamiri River at five

Laboratory Analysis
Serial dilution of the water samples were carried out using sterile distilled water as in (Chessbrough, 2002). The water and sediment samples were examined bacteriologically using culture techniques as in (Chessbrough, 2002). Each water sample was examined by culture technique using streak plate and spread plate technique   for 24 h and were then stored in the refrigerator until required for further use.
All the different dilutions were properly labelled and used for total plate count.
The bacteria isolates were subjected to various tests beginning from the study of their growth morphology on different agar media to different microbiological identification tests such as gram staining and motility tests and biochemical identification tests such as catalase, coagulase, oxidase, citrate utilization, urease, indole production, hydrogen sulphide production, nitrate and nitrite reduction, methyl red, Voges Proskeur and sugar fermentation tests (Table 5 and Table 6). (Table 1 and Table 2) Selective medium HiCrome coliform agar (Peptone 3 g/L, NaCl 5 g/L, dipotassium hydrogen phosphate 3 g/L, potassium dihydrogen phosphate 1.7 g/L, sodium pyruvate 1 g/L, l-tryptophan 1 g/L, sodium lauryl sulphate 0.1 g/L, chromogenic mixture 0.2 g/L, agar 15 g/L, pH 6.8).

Method of Result Analysis
The average mean of three samples per station (SSWS 1 -SSWS 2 ) was taken for three stations and one the reading for the remaining two stations (Control and Downstream
Although the WHO guideline indicates no standard, their presence in water indicates faecal contamination of the water. Escherichia coli, an indicator of these enterobacteria in water is harmless but the others have been implicated as the causative agent of one waterborne disease or the other (Duru et al., 2012).
According to Ahiarakwem (2013), the indiscriminate disposal of diapers at dumpsites in addition to defecations within and around the watershed of the river is responsible for its poor microbial assay. The presence of bacteria in water can cause cholera, hepatitis, dysentery and typhoid (Ahiarakwem, 2013). Journal of Geoscience and Environment Protection

Conclusion
The Otamiri River at the Five stations (SSWS 1 , SSWS 2 , SSWS 3 , Downstream and Control Point) is polluted with microbial constituents (bacteria such as: Escherichia coli, Vibro spp., Klebsiella spp., and Entrobacteria spp.). For the sediment, it shows pollution with respect to microbial constituents (bacteria such as: Escherichia coli, Vibro spp., Klebsiella spp., Entrobacteria spp. and Bacillus spp.). These pollutants are attributed to the waste and effluents disposed from land of the five stations. This calls for proper waste management practices and pre-use treatment of the river water with chlorine as well as boiling before usage in order to reduce the microbial constituents of the water. Therefore, there is a need for constant monitoring of the microbial characteristics of the river. In addition, communities along the river bank need to ensure that untreated wastes are not disposed of improperly on land where it can be washed into the river.
This work focused primarily on the sediments of the river. Therefore, subsequent research should be centered on the collection of samples per depth at other strategic locations of concern with respect to seasons. This is due to the over dredging of sands from the river which has resulted in erosion and sinkholes around the river.