Abstract

Njoro sub-county in Kenya suffers from constant water shortages causing the residents to rely on both improved and unimproved water sources in the area. The households in the sub-county also use different household storage containers to store drinking water in times when water is not readily available. This study was therefore undertaken to assess selective physico-chemical parameters of water used by the population for drinking purposes using standard assessment methods. A total of 372 water source samples and 162 storage container water samples were tested over a period of three months. Turbidity (0.70–273.85 NTU), iron (0.7–2.10 mg/L), fluoride (0.15–4.01 mg/L), manganese (0.01–0.37 mg/L), and nitrate (0.09–27.90 mg/L) levels in water samples were generally higher than the Kenya Bureau of Standards (KEBS) and/or the World Health Organization (WHO) water quality recommendations for safe drinkable water. The results from this study support the need for continuous monitoring and treating drinking water at the points of collection and of consumption to minimize the long-term health effects on communities consuming this water.

INTRODUCTION

In Kenya, many people lack access to potable water, mostly due to recurrent droughts, poor management of water sources, and the arid and semi-arid climate of some regions (Kalungu et al. 2014). Although the government spends a great deal of money to improve access to potable water, many rural households do not have access to sufficient volumes for their basic daily needs (Shadrack 2012). Several studies have assessed the quality of different water sources in Kenya (Mwaura 2003; Shivoga et al. 2007; Yillia et al. 2008; Kiruki et al. 2011; Donde et al. 2013). However, this is done intermittently and the majority of studies usually did a snap shot (due to cost and time factors) of the water quality. The WHO recommendations for drinking water quality encourage water testing on a regular basis to verify its quality (WHO 2011). These recommendations provide a framework for achieving safe drinking water through the implementation of health-based targets, creation of water safety plans, and the maintenance of water surveillance. In the Njoro sub-county of Kenya, drinking water is obtained mostly from harvested rain water, boreholes, springs, wells, dams, and rivers. These sources are polluted through contamination from sewage leakages, agricultural run offs and livestock wastes (Shadrack 2012). As a result, it is necessary to perform frequent assessments of water at the points of collection and of consumption to determine the suitability of the water for domestic use. Physico-chemical components of drinking water have an ability to cause adverse health effects after prolonged periods of exposure, especially chemicals that have toxic properties, such as metals and substances that are carcinogenic (Moturi et al. 2002). The aim of this study was, therefore, to assess specific physico-chemical parameters of improved and unimproved water sources and water stored inside various households in the Njoro sub-county of Kenya to determine the quality of drinking water used by rural and peri-urban communities.

MATERIALS AND METHODS

Study site

Njoro sub-county (Figure 1) is located at an elevation of 1,600 to 2,000 m above sea level and about 20 km southwest of Nakuru town in the Kenyan Rift Valley Province (Mainuri & Owino 2013).

Figure 1

Map of Njoro sub-county, Kenya.

Figure 1

Map of Njoro sub-county, Kenya.

The region is classified as semi-arid. It has a total annual rainfall that ranges from 500 mm in the lowlands to 1,800 mm in the highlands and occurs in two seasons, namely, the long rains from March to April and the short rains from October to December. The Njoro River is the major source of water but its volume reduces during dry seasons. The salty Lake Nakuru is the nearest lake to the sub-county (Shivoga et al. 2007; Yillia et al. 2008). The sub-county is divided into five administrative divisions: Njoro, Lare, Kihingo, Maunarok, and Mauche with a total population of approximately 188,124 people (KNSB 2009, 2013). The mainstay of the economy in this area is agri-based industries including vegetable and milk processing, large-scale maize, wheat, and barley farming, and light manufacturing industries such as timber milling, canning, and quarrying (WHO 2011). Due to rapid urbanization, Njoro sub-county has experienced a high population growth (Shivoga et al. 2007; Yillia et al. 2008). This has led to the generation of more industrial, household, fecal, and agricultural wastes which find their way into water bodies during the raining season (Razif & Persada 2015) where it affects the physico-chemical and microbiological quality of drinking water.

Sample collection

Simple random sampling was used to select the participating villages in this study. The sample size of this study was calculated using the formula n = z2p.q/d2 where n = desired sample size; z = standard normal deviation at 1.96 (obtained from a two-tailed normal table); q = 1 − p; d2 = 0.052, and p = prevalence of the condition under study (Kiruki et al. 2011). A total of 372 water samples were collected from 124 water sources and 162 samples from 54 household storage containers (Table 1).

Table 1

Water sources and household water storage containers assessed in Njoro sub-county

Water source and container n (%) Kihingo Njoro Lare Mauche Maunarok 
Unimproved source River 5 (38.46%) – – – 
Spring 1 (7.96%) – – – – 
Well 5 (38.46%) – – 
Dam 2 (15.38%) – – – 
Improved source Spring 6 (5.41%) – – 
Tap/piped water 28 (25.23%) 11 
Tank 45 (40.45%) 14 12 11 
Borehole 24 (21.62%) 17 
Well 8 (7.21%) – – – 
Household container Sufuria 2 (3.70%) – – – 
Cup 2 (3.70%) – – – 
Jug 2 (3.70%) – – – 
Clay pot 2 (3.70%) – – – 
Jerry can 40 (74.07%) 10 10 
Bucket 2 (3.70%) – – – 
Gallon 4 (7.41%) – – – 
Water source and container n (%) Kihingo Njoro Lare Mauche Maunarok 
Unimproved source River 5 (38.46%) – – – 
Spring 1 (7.96%) – – – – 
Well 5 (38.46%) – – 
Dam 2 (15.38%) – – – 
Improved source Spring 6 (5.41%) – – 
Tap/piped water 28 (25.23%) 11 
Tank 45 (40.45%) 14 12 11 
Borehole 24 (21.62%) 17 
Well 8 (7.21%) – – – 
Household container Sufuria 2 (3.70%) – – – 
Cup 2 (3.70%) – – – 
Jug 2 (3.70%) – – – 
Clay pot 2 (3.70%) – – – 
Jerry can 40 (74.07%) 10 10 
Bucket 2 (3.70%) – – – 
Gallon 4 (7.41%) – – – 

–, No samples collected because source type/container type not available to test.

Water sources in the study area were categorized as improved and unimproved sources according to the WHO criteria. An improved water source is defined as a source which as a result of a construction or intervention program is protected from external sources of contamination, while an unimproved water source is not protected in any way from external contaminants like fecal matter (WHO 2011). Sterile 500 mL plastic bottles were used for all water sample collections and all samples were transported immediately after collection on ice to the laboratory for further analysis within 6 hours of collection. Three samples were taken from each source and container type. Household water from storage containers were collected by visiting the homesteads and requesting consent from the home owner before taking a sample. A sterile collection bottle was used to collect a water sample from any domestic storage container that had water used for drinking and other household purposes. Water samples from water sources were collected from all sources used by the study communities as points of water collection. Wells were purged for at least 3 minutes to flush out any standing water from the bottom while taps were allowed to run for 2 minutes before sampling. The sample bottle was then rinsed with the water sample three times before taking the sample.

Sample analysis

Physico-chemical parameters used in this assessment included temperature, total dissolved solids (TDS), electrical conductivity (EC), pH, turbidity, dissolved oxygen (DO), biological oxygen demand (BOD), nitrate, manganese, fluoride, and iron. All measurements were based on standard procedures (APHA 1998). All water sample readings were taken in triplicate and averages entered into MS Excel.

Portable meters were used according to the manufacturer's instructions. Temperature, TDS, EC, and pH were measured at the point of sample collection using a multimeter (Combo, Hanna Instruments, USA) according to the manufacturer's instructions. The bulb end of the multi-meter was rinsed in sterile distilled water and carefully placed into the water sample, allowed to stabilize, and each of the readings taken after 2 minutes. The electrode of the pH meter was first calibrated against a pH buffer of 7, 9, and 12, respectively, at room temperature to adjust to the response of the glass electrode. DO was measured at the point of sample collection using a portable DO meter (Hach HQ 40d, USA). The probe was rinsed in distilled water and immersed into the water sample. The reading displayed on the screen was read and recorded in mg/L (KEBS 2010). Turbidity was measured in the laboratory using a turbidity meter (Hach 2100Q, USA). A total of 25 mL of the sample was gently agitated until all air bubbles disappeared. The sample was added to a sample cell and the turbidity read directly from the instrument display screen and recorded in nephelometric turbidity units (NTU). Five days BOD was determined using standard procedures. In brief, the samples were put in the aluminum foil-covered BOD bottle and incubated in the dark for 5 days at 20 °C. Readings were recorded in mg/L (Himedia, USA).

The water samples were not filtered so the mean concentrations of chemical water quality (nitrate, iron, manganese, and fluoride) are total dissolved constituents. Fluoride was assayed using the USEPA SPADNS method. The method involves the reaction between fluoride and a red zirconium dye solution. Fluoride combines with part of the zicornium to form a colorless complex that bleaches the red color in an amount proportional to the fluoride concentration. In brief, a pipette was used to draw approximately 10 mL of the water sample into a dry sample cell and 10 mL of deionized water (control) was drawn into another sample cell to serve as the control. A volume of 2 mL of SPADNS 2 reagent was added to each cell and swirled to mix the contents. Samples were read at 580 nm against the control using a spectrophotometer (Hach DR-3900) and results recorded. Nitrate was assayed using cadmium reduction method. Cadmium metal reduces nitrate in the water sample to nitrite which reacts in an acidic medium with sulfanilic acid to form an intermediate diazonium salt. The salt couples with gentisic acid to form an amber colored solution. In brief, the sample cell was filled with 10 mL of the sample followed by the addition of nitraVer 5 nitrate reagent powder (cadmium). The contents were swirled for 1 minute to obtain a uniform mixture. An amber color read at 500 nm using a spectrophotometer (Hach DR-3900) was indicative of the presence of nitrate. Manganese was analyzed using the periodate oxidation method. If manganese is present in the water sample, it is oxidized to the purple permanganate compound by the sodium periodate upon buffering with citrate. The intensity of the purple color is directly proportional to the manganese concentration in the respective water sample. In brief, 10 mL of the water sample and distilled water were added into separate sample cells and the citrate powder pillow followed by sodium periodate powder pillow poured into each of the cells. The samples were read at a wavelength of 525 nm using a spectrophotometer (Hach DR-3900) against the control. Iron was analyzed using the FerroVer method. In the case where iron is present in the water sample, the FerroVer reagent converts all the iron into soluble ferrous iron. The 1,10-phenanthroline indicator contained in the powder forms an orange color in proportion to the amount of iron present. Briefly, 10 mL of the sample was put in a sample cell followed by addition of the contents of the FerroVer iron reagent pillows. After dissolvement, the sample was read on a spectrophotometer at a wavelength of 510 nm using a spectrophotometer (Hach DR-3900) against the control.

Data analyses

The physico-chemical quality of drinking water was measured using the WHO water quality recommendations (WHO 2011) and the Kenya Bureau of Standards (KEBS) (KEBS 2010) as shown in Table 2. All the data generated during the study were coded and entered into MS Excel 2010 for cleaning, editing, and then imported into Statistical Analysis System (SAS) version 9.1 for analysis. The means and standard errors were determined and recorded. One-way analysis of variance (ANOVA) was carried out to test the significance differences and the level of significance was determined using the least significant design (LSD) at α = 0.05. The LSD method separates means by use of small letters (e.g., a,b,c). If the means within a column are followed by the same letter, they are not statistically different. Means followed by different letters in the same column indicates that the said variable level significantly affects the parameter(s) being analyzed.

Table 2

Drinking water recommendations used for assessment of quality of water samples

Parameters tested World Health Organization (WHO) (WHO 2011Kenya Bureau (KEBS) (KEBS 2010
Temperature Not specified Not specified 
pH 6.5–8.5 6.5–8.5 
Electrical conductivity (EC) Not specified Not specified 
Dissolved oxygen (DO) Not specified 6 mg/L 
Turbidity 5 NTU 5 NTU 
Biological oxygen demand (BOD) Not specified 30 mg/L 
Total dissolved solids (TDS) 600 mg/L 1,200 mg/L 
Nitrate-NO3 50 mg/L (brief exposure) 10 mg/L 
Dissolved manganese Not specified 0.1 mg/L 
Dissolved iron Not specified 0.3 mg/L 
Fluoride 1.5 mg/L 1.5 mg/L 
Parameters tested World Health Organization (WHO) (WHO 2011Kenya Bureau (KEBS) (KEBS 2010
Temperature Not specified Not specified 
pH 6.5–8.5 6.5–8.5 
Electrical conductivity (EC) Not specified Not specified 
Dissolved oxygen (DO) Not specified 6 mg/L 
Turbidity 5 NTU 5 NTU 
Biological oxygen demand (BOD) Not specified 30 mg/L 
Total dissolved solids (TDS) 600 mg/L 1,200 mg/L 
Nitrate-NO3 50 mg/L (brief exposure) 10 mg/L 
Dissolved manganese Not specified 0.1 mg/L 
Dissolved iron Not specified 0.3 mg/L 
Fluoride 1.5 mg/L 1.5 mg/L 

RESULTS AND DISCUSSION

This study assessed the physico-chemical parameters of improved and unimproved water sources and water stored within different household containers in Njoro sub-county in Kenya. Improved drinking water sources were the primary sources of drinking water for the population constituting 89.52% (n = 111) while unimproved sources formed 10.48% (n = 13). Improved drinking sources in this study included: taps/piped water (25.23%), tanks (40.54%), boreholes (21.62%), protected wells (7.21%), and protected springs (5.41%). Unimproved water sources in this study included: rivers (38.46%), unprotected wells (38.46%), dams (15.38%), and unprotected springs (7.69%). Several different household water storage containers were used in the study area (n = 54) and included: jugs (3.70%), cups (3.70%), plastic 5-liter gallons (7.41%), sufurias (silver in color and made of aluminum) (3.07%), jerry cans (74.07%), ceramic pots (3.70%), and buckets (3.70%) (Table 1).

Table 3 provides an overview of all chemical analyses in the study. The nitrate levels for the majority of unimproved water sources and springs in the Mauche region were above the KEBS recommendation limit (KEBS 2010). In this study, nitrate varied between 0.09 and 27.90 mg/L in the unimproved water sources, between 0.90 and 85 mg/L in the improved water sources, and between 0.25 and 9.25 mg/L in the water storage containers. Based on WHO guidelines, nitrate levels in protected springs were high (85 mg/L). Nitrates were above the recommended levels in various water sources: 27.90 mg/L in rivers in Mauche; 13.30 mg/L in unprotected springs in Njoro; 25.80 mg/L in dams in Mauche; and 85.00 mg/L in protected springs in Mauche (Table 3). This could be due to extensive agricultural activities carried out in these regions and hence excessive application of inorganic nitrogenous fertilizers, waste water treatment, and oxidation of human excreta (Khazenzi et al. 2014). Findings of a previous study on groundwater in Langas, Kenya had mean nitrate levels above 10 mg/L (Khazenzi et al. 2014) attributed to the leakage of nitrates from the pit latrines through the soil into water bodies. Nitrates are highly leachable and can find their way into surface as well as underground water sources leading to contamination (Maghanga et al. 2012).

Table 3

Chemical parameters for improved and unimproved water sources and household storage containers used in Njoro sub-county (mean ± standard error)

Water source and container Sub-county n Nitrate (mg/L) Manganese (mg/L) Iron (mg/L) Fluoride (mg/L) 
Unimproved water source River Mauche 27.90 ± 0.29b 0.03 ± 0.01a 0.87 ± 0.23a 2.42 ± 0.64a 
 Njoro 12 9.23 ± 1.38ab 0.27 ± 0.04a 0.89 ± 0.05a 0.88 ± 0.30b 
Spring Njoro 13.30 ± 1.38a 0.10 ± 0.02a 0.53 ± 0.19a 1.59 ± 0.12b 
Well Kihingo 5.13 ± 0.70a 0.08 ± 0.03a 0.77 ± 0.32a 0.84 ± 0.25a 
 Maunarok 0.09 ± 0.02 b 0.08 ± 0.01a 0.07 ± 0.02a 1.25 ± 0.10a 
 Njoro 2.00 ± 0.01b 0.10 ± 0.03a 0.16 ± 0.07a 4.01 ± 1.29a 
Dam Mauche 8.20 ± 0.21c 0.03 ± 0.01a 0.53 ± 0.23a 2.54 ± 0.17a 
  Maunarok 25.80 ± 3.89a 0.08 ± 0.03a 0.31 ± 0.13a 1.44 ± 0.11a 
Improved water source Spring Mauche 85.00 ± 5.00a 0.31 ± 0.05a 1.12 ± 0.02a 2.99 ± 0.17a 
 Maunarok 4.27 ± 0.60b 0.04 ± 0.01a 0.34 ± 0.15a 2.28 ± 0.32a 
 Njoro 8.60 ± 0.39b 0.07 ± 0.02a 0.54 ± 0.15a 2.75 ± 1.01ab 
Tap/piped water Kihingo 1.09 ± 0.11a 0.05 ± 0.01a 0.25 ± 0.04a 1.71 ± 0.32a 
 Lare 15 4.77 ± 0.58a 0.20 ± 0.05a 0.55 ± 0.05a 2.37 ± 0.57a 
 Mauche 27 3.90 ± 1.86c 0.11 ± 0.05a 0.54 ± 0.16a 2.11 ± 0.49a 
 Maunarok 1.20 ± 0.03b 0.05 ± 0.01a 0.25 ± 0.11a 1.89 ± 0.04a 
 Njoro 33 2.74 ± 1.00b 0.20 ± 0.05a 0.64 ± 0.20a 1.80 ± 0.37b 
Tank Kihingo 42 3.09 ± 1.29a 0.24 ± 0.05a 0.53 ± 0.09a 1.73 ± 0.27a 
 Lare 1.23 ± 0.44a 0.19 ± 0.03a 0.87 ± 0.34a 2.80 ± 0.10a 
 Mauche 18 3.42 ± 1.40c 0.29 ± 0.13a 0.64 ± 0.17a 2.20 ± 0.59a 
 Maunarok 33 1.70 ± 0.52b 0.07 ± 0.02a 0.30 ± 0.06a 0.80 ± 0.31a 
 Njoro 36 3.58 ± 1.30b 0.26 ± 0.06a 0.83 ± 0.18a 0.99 ± 0.21b 
Borehole Kihingo 6.40 ± 0.78a 0.36 ± 0.07a 0.67 ± 0.22a 1.62 ± 0.49a 
 Lare 6.12 ± 0.84a 0.19 ± 0.03a 0.58 ± 0.09a 1.18 ± 0.23a 
 Mauche 1.45 ± 0.15c 0.03 ± 0.01a 0.65 ± 0.08a 2.61 ± 0.31a 
 Maunarok 0.90 ± 0.21b 0.05 ± 0.01a 0.18 ± 0.03a 0.15 ± 0.04a 
 Njoro 51 2.32 ± 0.50b 0.06 ± 0.02a 0.40 ± 0.12a 1.86 ± 0.28b 
Well Kihingo 15 6.86 ± 0.70a 0.37 ± 0.14a 0.52 ± 0.13a 1.05 ± 0.47a 
  Maunarok 2.42 ± 0.21b 0.09 ± 0.03a 0.25 ± 0.03a 1.84 ± 0.59a 
Container Gallon Kihingo 5.31 ± 0.97a 0.1 ± 0.01a 0.25 ± 0.03a 1.29 ± 0.46a 
 Lare 2.69 ± 0.09a 0.04 ± 0.01a 0.26 ± 0.05a 2.43 ± 1.01a 
Jug Mauche 1.85 ± 0.38a 0.32 ± 0.08a 0.53 ± 0.17a 3.39 ± 0.14a 
 Njoro 5.63 ± 0.39a 0.03 ± 0.01a 1.56 ± 0.35ab 0.42 ± 0.16a 
Cup/mug Lare 4.21 ± 0.91a 0.06 ± 0.02a 0.04 ± 0.01a 1.80 ± 0.33a 
 Mauche 0.65 ± 0.19a 0.05 ± 0.02a 1.05 ± 0.02a 0.23 ± 0.10b 
Jerry can Kihingo 27 3.49 ± 1.33a 0.30 ± 0.10a 0.55 ± 0.13a 2.04 ± 0.37a 
 Lare 12 7.20 ± 1.88a 0.17 ± 0.02a 1.61 ± 0.47a 1.67 ± 0.16a 
 Mauche 21 4.60 ± 0.48a 0.20 ± 0.02a 0.83 ± 0.16a 3.19 ± 0.23a 
 Maunarok 30 3.82 ± 0.36 0.13 ± 0.04 0.34 ± 0.09 1.2 0 ± 0.33 
 Njoro 30 2.56 ± 0.77a 0.17 ± 0.04a 0.43 ± 0.11b 1.34 ± 0.06a 
Clay pot Mauche 0.25 ± 0.08a 0.15 ± 0.03a 0.39 ± 0.17a 3.11 ± 0.13a 
 Njoro 0.96 ± 0.22a 0.05 ± 0.02a 1.15 ± 0.02b 3.12 ± 1.05a 
Bucket Lare 9.25 ± 1.28a 0.04 ± 0.01a 1.06 ± 0.01a 1.63 ± 0.19a 
 Njoro 0.33 ± 0.11a 0.04 ± 0.01a 0.89 ± 0.29b 1.87 ± 0.04a 
Sufuria Mauche 0.88 ± 0.21a 0.04 ± 0.01a 0.24 ± 0.06a 0.44 ± 0.17b 
  Njoro 8.12 ± 3.11a 0.03 ± 0.01a 2.10 ± 0.17a 1.73 ± 0.08a 
Water source and container Sub-county n Nitrate (mg/L) Manganese (mg/L) Iron (mg/L) Fluoride (mg/L) 
Unimproved water source River Mauche 27.90 ± 0.29b 0.03 ± 0.01a 0.87 ± 0.23a 2.42 ± 0.64a 
 Njoro 12 9.23 ± 1.38ab 0.27 ± 0.04a 0.89 ± 0.05a 0.88 ± 0.30b 
Spring Njoro 13.30 ± 1.38a 0.10 ± 0.02a 0.53 ± 0.19a 1.59 ± 0.12b 
Well Kihingo 5.13 ± 0.70a 0.08 ± 0.03a 0.77 ± 0.32a 0.84 ± 0.25a 
 Maunarok 0.09 ± 0.02 b 0.08 ± 0.01a 0.07 ± 0.02a 1.25 ± 0.10a 
 Njoro 2.00 ± 0.01b 0.10 ± 0.03a 0.16 ± 0.07a 4.01 ± 1.29a 
Dam Mauche 8.20 ± 0.21c 0.03 ± 0.01a 0.53 ± 0.23a 2.54 ± 0.17a 
  Maunarok 25.80 ± 3.89a 0.08 ± 0.03a 0.31 ± 0.13a 1.44 ± 0.11a 
Improved water source Spring Mauche 85.00 ± 5.00a 0.31 ± 0.05a 1.12 ± 0.02a 2.99 ± 0.17a 
 Maunarok 4.27 ± 0.60b 0.04 ± 0.01a 0.34 ± 0.15a 2.28 ± 0.32a 
 Njoro 8.60 ± 0.39b 0.07 ± 0.02a 0.54 ± 0.15a 2.75 ± 1.01ab 
Tap/piped water Kihingo 1.09 ± 0.11a 0.05 ± 0.01a 0.25 ± 0.04a 1.71 ± 0.32a 
 Lare 15 4.77 ± 0.58a 0.20 ± 0.05a 0.55 ± 0.05a 2.37 ± 0.57a 
 Mauche 27 3.90 ± 1.86c 0.11 ± 0.05a 0.54 ± 0.16a 2.11 ± 0.49a 
 Maunarok 1.20 ± 0.03b 0.05 ± 0.01a 0.25 ± 0.11a 1.89 ± 0.04a 
 Njoro 33 2.74 ± 1.00b 0.20 ± 0.05a 0.64 ± 0.20a 1.80 ± 0.37b 
Tank Kihingo 42 3.09 ± 1.29a 0.24 ± 0.05a 0.53 ± 0.09a 1.73 ± 0.27a 
 Lare 1.23 ± 0.44a 0.19 ± 0.03a 0.87 ± 0.34a 2.80 ± 0.10a 
 Mauche 18 3.42 ± 1.40c 0.29 ± 0.13a 0.64 ± 0.17a 2.20 ± 0.59a 
 Maunarok 33 1.70 ± 0.52b 0.07 ± 0.02a 0.30 ± 0.06a 0.80 ± 0.31a 
 Njoro 36 3.58 ± 1.30b 0.26 ± 0.06a 0.83 ± 0.18a 0.99 ± 0.21b 
Borehole Kihingo 6.40 ± 0.78a 0.36 ± 0.07a 0.67 ± 0.22a 1.62 ± 0.49a 
 Lare 6.12 ± 0.84a 0.19 ± 0.03a 0.58 ± 0.09a 1.18 ± 0.23a 
 Mauche 1.45 ± 0.15c 0.03 ± 0.01a 0.65 ± 0.08a 2.61 ± 0.31a 
 Maunarok 0.90 ± 0.21b 0.05 ± 0.01a 0.18 ± 0.03a 0.15 ± 0.04a 
 Njoro 51 2.32 ± 0.50b 0.06 ± 0.02a 0.40 ± 0.12a 1.86 ± 0.28b 
Well Kihingo 15 6.86 ± 0.70a 0.37 ± 0.14a 0.52 ± 0.13a 1.05 ± 0.47a 
  Maunarok 2.42 ± 0.21b 0.09 ± 0.03a 0.25 ± 0.03a 1.84 ± 0.59a 
Container Gallon Kihingo 5.31 ± 0.97a 0.1 ± 0.01a 0.25 ± 0.03a 1.29 ± 0.46a 
 Lare 2.69 ± 0.09a 0.04 ± 0.01a 0.26 ± 0.05a 2.43 ± 1.01a 
Jug Mauche 1.85 ± 0.38a 0.32 ± 0.08a 0.53 ± 0.17a 3.39 ± 0.14a 
 Njoro 5.63 ± 0.39a 0.03 ± 0.01a 1.56 ± 0.35ab 0.42 ± 0.16a 
Cup/mug Lare 4.21 ± 0.91a 0.06 ± 0.02a 0.04 ± 0.01a 1.80 ± 0.33a 
 Mauche 0.65 ± 0.19a 0.05 ± 0.02a 1.05 ± 0.02a 0.23 ± 0.10b 
Jerry can Kihingo 27 3.49 ± 1.33a 0.30 ± 0.10a 0.55 ± 0.13a 2.04 ± 0.37a 
 Lare 12 7.20 ± 1.88a 0.17 ± 0.02a 1.61 ± 0.47a 1.67 ± 0.16a 
 Mauche 21 4.60 ± 0.48a 0.20 ± 0.02a 0.83 ± 0.16a 3.19 ± 0.23a 
 Maunarok 30 3.82 ± 0.36 0.13 ± 0.04 0.34 ± 0.09 1.2 0 ± 0.33 
 Njoro 30 2.56 ± 0.77a 0.17 ± 0.04a 0.43 ± 0.11b 1.34 ± 0.06a 
Clay pot Mauche 0.25 ± 0.08a 0.15 ± 0.03a 0.39 ± 0.17a 3.11 ± 0.13a 
 Njoro 0.96 ± 0.22a 0.05 ± 0.02a 1.15 ± 0.02b 3.12 ± 1.05a 
Bucket Lare 9.25 ± 1.28a 0.04 ± 0.01a 1.06 ± 0.01a 1.63 ± 0.19a 
 Njoro 0.33 ± 0.11a 0.04 ± 0.01a 0.89 ± 0.29b 1.87 ± 0.04a 
Sufuria Mauche 0.88 ± 0.21a 0.04 ± 0.01a 0.24 ± 0.06a 0.44 ± 0.17b 
  Njoro 8.12 ± 3.11a 0.03 ± 0.01a 2.10 ± 0.17a 1.73 ± 0.08a 

Manganese results in this assessment varied between 0.03 and 0.27 mg/L in the unimproved water sources, between 0.03 and 0.37 mg/L in the improved water sources, and between 0.03 and 0.32 mg/L in the water storage containers. Manganese concentrations in river (Njoro), spring (Mauche), tap water (Lare and Njoro), tank water (Kihingo, Lare, Mauche, and Njoro), borehole water (Kihingo), protected wells (Kihingo), gallons (Kihingo), jugs (Mauche), jerry cans (Kihingo, Lare, Mauche, Maunarok, and Njoro), and clay pots (Mauche) are shown in Table 3. Dissolved manganese occurs naturally in the ground rocks and can come into contact with underground and surface drinking water (Perlman 2014). Manganese alters the esthetic properties of drinking water, and, in very high concentrations, and for prolonged periods of time, can cause intellectual impairment (Bouchard et al. 2011).

Iron levels in unimproved water sources varied between 0.07 and 0.89 mg/L, between 0.18 and 1.12 mg/L in the improved water sources, and between 0.04 and 2.10 mg/L in the water storage containers. Iron measurements were higher than KEBS guidelines apart from unprotected wells (Maunarok and Njoro), tap water (Kihingo and Maunarok), borehole water (Maunarok), and protected wells (Maunarok) (Table 3). Dissolved iron is an abundant mineral in the Earth's crust and when it enters into water, it forms an insoluble precipitate of ferric iron (Wendt et al. 2016). The findings of this study are similar to a study in Ota, Nigeria reporting high iron levels in drinking water and groundwater (Anake et al. 2014). The high levels of iron containers across the locations could be due to infiltration of iron from soil and pipes into the water supplies before collection (Wendt et al. 2016).

Fluoride levels varied between 0.84 and 4.01 mg/L in the unimproved water sources, between 0.15 and 2.99 mg/L in the improved water sources, and between 0.23 and 3.39 mg/L in the water storage containers. The highest mean fluoride measurement in unimproved sources was 4.01 mg/L (unprotected wells in Njoro), in improved sources the highest measurement was 2.99 mg/L (protected springs in Mauche), and at households the highest measurement was 3.39 mg/L (jug water in Mauche) (Meenaksi & Maheshwari 2006; KEBS 2010) (Table 3). Fluoride is a mineral found on the Earth's crust and can find its way into underground drinking water sources (Njenga et al. 2005). In levels above 1.5 mg/L, fluoride causes dental fluorosis characterized by brown teeth whereby fluoride replaces the hydroxyl group on the enamel with the hydroxyapatite (Moturi et al. 2002). High fluoride is due to the location of Njoro sub-county in the East African Great Rift Valley whereby the underground water from aquifers interacts with the fluoride-bearing rocks (Meenaksi & Maheshwari 2006).

The physical assessment in this study is shown in Tables 4 and 5. The mean temperatures in this study ranged from 16.35 to 24.7 °C in unimproved water sources. The mean temperature in improved water sources ranged from 19.16 to 27.55 °C and in household storage containers ranged from 14.10 to 27.20 °C. Water stored in buckets in Lare had the highest temperature. The high temperatures in rivers could be a result of discharge of human, agricultural, and industrial effluents (Shivoga et al. 2007). Water may have a higher temperature because the suspended and dissolved materials can absorb heat from the sun (Munoz et al. 2015). Higher water temperatures are less pleasing to consumers and warm water encourages microorganism growth (Shivoga et al. 2007; Yillia et al. 2008).

Table 4

Physico-chemical parameters for improved and unimproved water sources in Njoro sub-county (mean ± standard error)

Water source Sub-county n Temp (°C) pH EC (μS/cm) DO (mg/L) Turb (NTU) BOD (mg/L) TDS (mg/L) 
Unimproved source River Mauche 24.70 ± 1.87a 7.51 ± 0.34ab 310 ± 0.06a 5.83 ± 1.46a 44.70 ± 2.87b 0.30 ± 0.06a 150 ± 0.02a 
 Njoro 12 16.35 ± 1.09b 8.17 ± 0.09a 3,360 ± 0.64a 7.27 ± 0.16a 94.53 ± 22.80a 0.87 ± 0.23a 70 ± 0.01b 
Spring Njoro 24.00 ± 1.64a 6.74 ± 0.71b 340 ± 0.02a 6.81 ± 0.39a 72.40 ± 10.31ab 0.50 ± 0.19a 170 ± 0.04b 
Well Kihingo 22.23 ± 0.75a 7.56 ± 0.11a 760 ± 0.19a 3.23 ± 0.23b 1.80 ± 0.21a 0.82 ± 0.07b 370 ± 0.11a 
 Maunarok 22.00 ± 0.31a 7.67 ± 1.84a 180 ± 0.06ab 6.71 ± 1.56a 9.50 ± 2.31b 0.63 ± 0.01ab 90 ± 0.03ab 
 Njoro 18.00 ± 2.81b 6.65 ± 0.15b 210 ± 0.03a 2.59 ± 0.06b 36.70 ± 9.59c 1.82 ± 0.12a 100 ± 0.03b 
Dam Mauche 19.00 ± 2.83a 7.89 ± 0.32a 270 ± 0.04a 6.93 ± 1.83a 20.30 ± 2.81b 1.49 ± 0.07a 140 ± 0.03a 
  Maunarok 22.50 ± 1.73a 7.81 ± 0.41a 210 ± 0.04a 6.25 ± 1.24a 59.70 ± 3.62a 0.17 ± 0.02b 100 ± 0.03a 
Improved source Spring Mauche 25.20 ± 7.50a 7.34 ± 0.52a 350 ± 0.03a 6.27 ± 0.66a 273.85 ± 52.85a 1.94 ± 0.21a 180 ± 0.08a 
 Maunarok 19.43 ± 0.34a 7.10 ± 0.32a 160 ± 0.01b 6.47 ± 0.18a 11.70 ± 1.14b 0.26 ± 0.04b 70 ± 0.01b 
 Njor 22.10 ± 1.07b 7.12 ± 0.06b 880 ± 0.19a 6.84 ± 1.31a 37.90 ± 2.87bc 0.47 ± 0.11a 440 ± 0.03a 
Tap/piped water Kihingo 21.55 ± 0.25a 7.91 ± 0.66a 680 ± 0.07a 5.41 ± 1.56a 0.55 ± 0.05a 2.16 ± 0.23a 340 ± 0.04a 
 Lare 15 21.88 ± 0.75a 7.85 ± 0.24a 170 ± 0.06a 4.48 ± 0.89a 21.92 ± 4.14a 1.01 ± 0.37a 80 ± 0.01a 
 Mauche 27 21.21 ± 0.70a 7.78 ± 0.14a 250 ± 0.05a 5.65 ± 0.35a 5.79 ± 1.12b 1.02 ± 0.20a 120 ± 0.03a 
 Maunarok 21.20 ± 0.37a 8.73 ± 0.28a 190 ± 0.01a 7.04 ± 1.39a 0.30 ± 0.08b 0.91 ± 0.06a 100 ± 0.01a 
 Njoro 33 22.28 ± 0.72ab 8.36 ± 0.15a 320 ± 0.03a 6.20 ± 0.28a 4.96 ± 0.59c 1.10 ± 0.36a 160 ± 0.01b 
Tank Kihingo 42 20.73 ± 0.59a 8.05 ± 0.17a 150 ± 0.05b 6.31 ± 0.29a 4.99 ± 1.90a 0.94 ± 0.16b 80 ± 0.03b 
 Lare 23.35 ± 3.55a 7.83 ± 0.27a 250 ± 0.05a 5.93 ± 0.74a 1.50 ± 0.20a 0.81 ± 0.06a 130 ± 0.02a 
 Mauche 18 20.82 ± 0.60a 7.60 ± 0.08a 350 ± 0.04a 6.16 ± 0.18a 4.38 ± 1.25b 1.61 ± 0.34a 180 ± 0.02a 
 Maunarok 33 19.16 ± 0.92a 7.79 ± 0.13a 60 ± 0.02b 5.90 ± 0.26a 3.83 ± 0.81b 0.92 ± 0.07a 30 ± 0.01b 
 Njoro 36 20.51 ± 0.75b 7.60 ± 0.19b 100 ± 0.04a 5.27 ± 0.34a 2.90 ± 0.77c 1.02 ± 0.15a 50 ± 0.01b 
Borehole Kihingo 23.85 ± 0.05a 8.09 ± 0.06a 510 ± 0.04ab 6.05 ± 0.30a 0.40 ± 0.08a 0.35 ± 0.10b 250 ± 0.02 ab 
 Lare 27.55 ± 0.55a 8.42 ± 0.06a 470 ± 0.03a 6.21 ± 0.30a 6.70 ± 1.28a 1.12 ± 0.07a 240 ± 0.02a 
 Mauche 23.70 ± 0.90a 7.53 ± 0.02a 180 ± 0.02a 6.85 ± 0.01a 7.90 ± 0.60b 0.61 ± 0.08a 90 ± 0.01a 
 Maunarok 19.80 ± 2.57a 8.24 ± 1.33a 190 ± 0.02a 6.41 ± 1.39a 0.20 ± 0.08b 0.17 ± 0.06b 100 ± 0.02a 
 Njoro 51 24.22 ± 0.52a 7.67 ± 0.14b 370 ± 0.03a 6.39 ± 0.33a 5.99 ± 0.70c 0.84 ± 0.10a 190 ± 0.01b 
Well Kihingo 15 20.86 ± 0.49a 7.42 ± 0.15a 860 ± 0.13a 2.67 ± 0.46b 13.26 ± 1.14a 0.76 ± 0.23b 390 ± 0.04a 
  Maunarok 22.97 ± 1.10a 7.73 ± 0.32a 220 ± 0.01a 6.30 ± 0.18a 11.70 ± 1.14b 0.26 ± 0.04a 110 ± 0.01a 
Water source Sub-county n Temp (°C) pH EC (μS/cm) DO (mg/L) Turb (NTU) BOD (mg/L) TDS (mg/L) 
Unimproved source River Mauche 24.70 ± 1.87a 7.51 ± 0.34ab 310 ± 0.06a 5.83 ± 1.46a 44.70 ± 2.87b 0.30 ± 0.06a 150 ± 0.02a 
 Njoro 12 16.35 ± 1.09b 8.17 ± 0.09a 3,360 ± 0.64a 7.27 ± 0.16a 94.53 ± 22.80a 0.87 ± 0.23a 70 ± 0.01b 
Spring Njoro 24.00 ± 1.64a 6.74 ± 0.71b 340 ± 0.02a 6.81 ± 0.39a 72.40 ± 10.31ab 0.50 ± 0.19a 170 ± 0.04b 
Well Kihingo 22.23 ± 0.75a 7.56 ± 0.11a 760 ± 0.19a 3.23 ± 0.23b 1.80 ± 0.21a 0.82 ± 0.07b 370 ± 0.11a 
 Maunarok 22.00 ± 0.31a 7.67 ± 1.84a 180 ± 0.06ab 6.71 ± 1.56a 9.50 ± 2.31b 0.63 ± 0.01ab 90 ± 0.03ab 
 Njoro 18.00 ± 2.81b 6.65 ± 0.15b 210 ± 0.03a 2.59 ± 0.06b 36.70 ± 9.59c 1.82 ± 0.12a 100 ± 0.03b 
Dam Mauche 19.00 ± 2.83a 7.89 ± 0.32a 270 ± 0.04a 6.93 ± 1.83a 20.30 ± 2.81b 1.49 ± 0.07a 140 ± 0.03a 
  Maunarok 22.50 ± 1.73a 7.81 ± 0.41a 210 ± 0.04a 6.25 ± 1.24a 59.70 ± 3.62a 0.17 ± 0.02b 100 ± 0.03a 
Improved source Spring Mauche 25.20 ± 7.50a 7.34 ± 0.52a 350 ± 0.03a 6.27 ± 0.66a 273.85 ± 52.85a 1.94 ± 0.21a 180 ± 0.08a 
 Maunarok 19.43 ± 0.34a 7.10 ± 0.32a 160 ± 0.01b 6.47 ± 0.18a 11.70 ± 1.14b 0.26 ± 0.04b 70 ± 0.01b 
 Njor 22.10 ± 1.07b 7.12 ± 0.06b 880 ± 0.19a 6.84 ± 1.31a 37.90 ± 2.87bc 0.47 ± 0.11a 440 ± 0.03a 
Tap/piped water Kihingo 21.55 ± 0.25a 7.91 ± 0.66a 680 ± 0.07a 5.41 ± 1.56a 0.55 ± 0.05a 2.16 ± 0.23a 340 ± 0.04a 
 Lare 15 21.88 ± 0.75a 7.85 ± 0.24a 170 ± 0.06a 4.48 ± 0.89a 21.92 ± 4.14a 1.01 ± 0.37a 80 ± 0.01a 
 Mauche 27 21.21 ± 0.70a 7.78 ± 0.14a 250 ± 0.05a 5.65 ± 0.35a 5.79 ± 1.12b 1.02 ± 0.20a 120 ± 0.03a 
 Maunarok 21.20 ± 0.37a 8.73 ± 0.28a 190 ± 0.01a 7.04 ± 1.39a 0.30 ± 0.08b 0.91 ± 0.06a 100 ± 0.01a 
 Njoro 33 22.28 ± 0.72ab 8.36 ± 0.15a 320 ± 0.03a 6.20 ± 0.28a 4.96 ± 0.59c 1.10 ± 0.36a 160 ± 0.01b 
Tank Kihingo 42 20.73 ± 0.59a 8.05 ± 0.17a 150 ± 0.05b 6.31 ± 0.29a 4.99 ± 1.90a 0.94 ± 0.16b 80 ± 0.03b 
 Lare 23.35 ± 3.55a 7.83 ± 0.27a 250 ± 0.05a 5.93 ± 0.74a 1.50 ± 0.20a 0.81 ± 0.06a 130 ± 0.02a 
 Mauche 18 20.82 ± 0.60a 7.60 ± 0.08a 350 ± 0.04a 6.16 ± 0.18a 4.38 ± 1.25b 1.61 ± 0.34a 180 ± 0.02a 
 Maunarok 33 19.16 ± 0.92a 7.79 ± 0.13a 60 ± 0.02b 5.90 ± 0.26a 3.83 ± 0.81b 0.92 ± 0.07a 30 ± 0.01b 
 Njoro 36 20.51 ± 0.75b 7.60 ± 0.19b 100 ± 0.04a 5.27 ± 0.34a 2.90 ± 0.77c 1.02 ± 0.15a 50 ± 0.01b 
Borehole Kihingo 23.85 ± 0.05a 8.09 ± 0.06a 510 ± 0.04ab 6.05 ± 0.30a 0.40 ± 0.08a 0.35 ± 0.10b 250 ± 0.02 ab 
 Lare 27.55 ± 0.55a 8.42 ± 0.06a 470 ± 0.03a 6.21 ± 0.30a 6.70 ± 1.28a 1.12 ± 0.07a 240 ± 0.02a 
 Mauche 23.70 ± 0.90a 7.53 ± 0.02a 180 ± 0.02a 6.85 ± 0.01a 7.90 ± 0.60b 0.61 ± 0.08a 90 ± 0.01a 
 Maunarok 19.80 ± 2.57a 8.24 ± 1.33a 190 ± 0.02a 6.41 ± 1.39a 0.20 ± 0.08b 0.17 ± 0.06b 100 ± 0.02a 
 Njoro 51 24.22 ± 0.52a 7.67 ± 0.14b 370 ± 0.03a 6.39 ± 0.33a 5.99 ± 0.70c 0.84 ± 0.10a 190 ± 0.01b 
Well Kihingo 15 20.86 ± 0.49a 7.42 ± 0.15a 860 ± 0.13a 2.67 ± 0.46b 13.26 ± 1.14a 0.76 ± 0.23b 390 ± 0.04a 
  Maunarok 22.97 ± 1.10a 7.73 ± 0.32a 220 ± 0.01a 6.30 ± 0.18a 11.70 ± 1.14b 0.26 ± 0.04a 110 ± 0.01a 
Table 5

Physico-chemical parameters for water in household storage containers in Njoro sub-county (mean ± standard error)

Container Sub-county n Temp (°C) pH EC (μS/cm) DO (mg/L) Turb (NTU) BOD (mg/L) TDS (mg/L) 
Gallon Kihingo 23.90 ± 0.75a 8.10 ± 0.08a 530 ± 0.05a 5.13 ± 0.98a 7.87 ± 1.42a 0.62 ± 0.05a 260 ± 0.03a 
 Lare 18.50 ± 1.14a 8.09 ± 0.08a 110 ± 0.03a 7.05 ± 1.12a 2.70 ± 0.10a 0.73 ± 0.21a 50 ± 0.01a 
Jug Mauche 19.00 ± 1.18a 7.13 ± 0.42a 30 ± 0.01a 5.32 ± 0.13a 0.80 ± 0.10a 3.08 ± 0.02a 40 ± 0.01a 
 Njoro 24.20 ± 0.43a 8.21 ± 0.89a 320 ± 0.11a 6.03 ± 0.34a 1.50 ± 0.08a 0.58 ± 0.15b 160 ± 0.01a 
Cup or mug Lare 20.90 ± 1.19a 8.65 ± 1.12a 440 ± 0.11a 6.64 ± 1.81a 0.70 ± 0.02a 2.31 ± 0.31a 220 ± 0.02a 
 Mauche 21.00 ± 0.63a 8.35 ± 0.27a 180 ± 0.04a 6.83 ± 0.76a 7.10 ± 1.59a 3.08 ± 0.04a 90 ± 0.03a 
Jerrycan Kihingo 27 21.14 ± 0.61b 7.97 ± 0.16a 280 ± 0.09a 6.12 ± 0.41a 6.74 ± 0.67a 0.87 ± 0.28a 140 ± 0.05a 
 Lare 12 23.78 ± 1.00a 7.90 ± 0.18a 400 ± 0.04a 4.59 ± 0.38a 12.88 ± 2.40 1.47 ± 0.42 200 ± 0.02a 
 Mauche 21 21.14 ± 1.08a 7.87 ± 0.10a 160 ± 0.02a 7.10 ± 0.70a 4.74 ± 0.65 2.59 ± 0.58 80 ± 0.01a 
 Maunarok 30 19.01 ± 1.06 7.84 ± 0.14 130 ± 0.04 6.24 ± 0.31 3.62 ± 0.9 0.63 ± 0.0 70 ± 0.02 
 Njoro 30 21.51 ± 0.81a 7.97 ± 0.14a 370 ± 0.05a 5.86 ± 0.28a 2.33 ± 0.94a 0.85 ± 0.26b 180 ± 0.03a 
Claypot Mauche 14.10 ± 0.30a 7.76 ± 0.82a 190 ± 0.03a 5.66 ± 0.34a 4.20 ± 1.39a 2.19 ± 0.11a 90 ± 0.03a 
 Njoro 21.70 ± 0.83a  8.67 ± 0.49a 350 ± 0.13a 5.91 ± 0.89a 8.80 ± 2.34a 1.06 ± 0.02b 180 ± 0.07a 
Bucket Lare 27.20 ± 1.94a 7.18 ± 0.33a 30 ± 0.01a 6.16 ± 0.86a 3.00 ± 0.39a 2.00 ± 0.16a 40 ± 0.01a 
 Njoro 20.60 ± 1.21a 8.04 ± 0.54a 90 ± 0.03a 5.77 ± 0.48a 6.80 ± 1.38a 5.62 ± 0.11a 50 ± 0.01a 
Sufuria Mauche 16.10 ± 2.32a 8.04 ± 0.12a 190 ± 0.09a 6.22 ± 0.11a 3.70 ± 1.41a 3.45 ± 0.14a 100 ± 0.03a 
 Njoro 17.30 ± 0.92a 8.12 ± 0.59a 70 ± 0.02a 6.89 ± 0.79a 2.00 ± 0.41a 0.73 ± 0.28b 30 ± 0.01a 
Container Sub-county n Temp (°C) pH EC (μS/cm) DO (mg/L) Turb (NTU) BOD (mg/L) TDS (mg/L) 
Gallon Kihingo 23.90 ± 0.75a 8.10 ± 0.08a 530 ± 0.05a 5.13 ± 0.98a 7.87 ± 1.42a 0.62 ± 0.05a 260 ± 0.03a 
 Lare 18.50 ± 1.14a 8.09 ± 0.08a 110 ± 0.03a 7.05 ± 1.12a 2.70 ± 0.10a 0.73 ± 0.21a 50 ± 0.01a 
Jug Mauche 19.00 ± 1.18a 7.13 ± 0.42a 30 ± 0.01a 5.32 ± 0.13a 0.80 ± 0.10a 3.08 ± 0.02a 40 ± 0.01a 
 Njoro 24.20 ± 0.43a 8.21 ± 0.89a 320 ± 0.11a 6.03 ± 0.34a 1.50 ± 0.08a 0.58 ± 0.15b 160 ± 0.01a 
Cup or mug Lare 20.90 ± 1.19a 8.65 ± 1.12a 440 ± 0.11a 6.64 ± 1.81a 0.70 ± 0.02a 2.31 ± 0.31a 220 ± 0.02a 
 Mauche 21.00 ± 0.63a 8.35 ± 0.27a 180 ± 0.04a 6.83 ± 0.76a 7.10 ± 1.59a 3.08 ± 0.04a 90 ± 0.03a 
Jerrycan Kihingo 27 21.14 ± 0.61b 7.97 ± 0.16a 280 ± 0.09a 6.12 ± 0.41a 6.74 ± 0.67a 0.87 ± 0.28a 140 ± 0.05a 
 Lare 12 23.78 ± 1.00a 7.90 ± 0.18a 400 ± 0.04a 4.59 ± 0.38a 12.88 ± 2.40 1.47 ± 0.42 200 ± 0.02a 
 Mauche 21 21.14 ± 1.08a 7.87 ± 0.10a 160 ± 0.02a 7.10 ± 0.70a 4.74 ± 0.65 2.59 ± 0.58 80 ± 0.01a 
 Maunarok 30 19.01 ± 1.06 7.84 ± 0.14 130 ± 0.04 6.24 ± 0.31 3.62 ± 0.9 0.63 ± 0.0 70 ± 0.02 
 Njoro 30 21.51 ± 0.81a 7.97 ± 0.14a 370 ± 0.05a 5.86 ± 0.28a 2.33 ± 0.94a 0.85 ± 0.26b 180 ± 0.03a 
Claypot Mauche 14.10 ± 0.30a 7.76 ± 0.82a 190 ± 0.03a 5.66 ± 0.34a 4.20 ± 1.39a 2.19 ± 0.11a 90 ± 0.03a 
 Njoro 21.70 ± 0.83a  8.67 ± 0.49a 350 ± 0.13a 5.91 ± 0.89a 8.80 ± 2.34a 1.06 ± 0.02b 180 ± 0.07a 
Bucket Lare 27.20 ± 1.94a 7.18 ± 0.33a 30 ± 0.01a 6.16 ± 0.86a 3.00 ± 0.39a 2.00 ± 0.16a 40 ± 0.01a 
 Njoro 20.60 ± 1.21a 8.04 ± 0.54a 90 ± 0.03a 5.77 ± 0.48a 6.80 ± 1.38a 5.62 ± 0.11a 50 ± 0.01a 
Sufuria Mauche 16.10 ± 2.32a 8.04 ± 0.12a 190 ± 0.09a 6.22 ± 0.11a 3.70 ± 1.41a 3.45 ± 0.14a 100 ± 0.03a 
 Njoro 17.30 ± 0.92a 8.12 ± 0.59a 70 ± 0.02a 6.89 ± 0.79a 2.00 ± 0.41a 0.73 ± 0.28b 30 ± 0.01a 

The mean pH readings varied between 6.65 and 8.17 in the unimproved water sources, 7.10 and 8.73 in the improved water sources, and 7.13 and 8.67 in the storage containers (Tables 4 and 5). The mean pH in water sources and domestic containers was above the WHO and KEBS recommended values of 6.5 to 8.5 in tap water in Maunarok (8.73), 8.65 (cups/mugs in Lare), and 8.67 (clay pots in Njoro). The pH of water is measured on a scale ranging from 0 to 14 and a pH of less than 7 is acidic whereas more than 7 is alkaline. The pH is important in the effectiveness of disinfection and impacts corrosion of pipes (KEBS 2010). The observed levels for pH indicated that the majority of samples are neutral and slightly alkaline.

EC varied between 180 and 3,360 μS/cm in the unimproved water sources, 60 to 880 μS/cm in the improved water sources, and 20 to 530 μS/cm in the water storage containers (Tables 4 and 5). EC is a measure of the capacity of water to carry electric charge and indicates the amount of TDS. Although there are no WHO and KEBS guidelines on EC, high levels make drinking water increasingly unpleasant. The EC is affected by motion, total concentration, mobility, temperature, and valence of the solution of ions (Morrison et al. 2001).

The mean DO varied from 2.59 to 7.27 mg/L in unimproved water sources, 2.67 to 7.04 mg/L in improved water sources, and between 4.59 to 7.10 mg/L in domestic storage containers (Tables 4 and 5). DO forms an important aspect of humans, animals, and water bodies like fish for respiration (Munoz et al. 2015). Low DO is caused by sewage leakage, run off from fertilizers, and inorganic wastes from industrial and domestic activities. Although DO enters water by photosynthesis and diffusion from air, for diffusion to occur, temperature and the solubility nature of oxygen are critical (Zhang et al. 2015).

The turbidity in unimproved water sources ranged from 1.80 to 94.53 mg/L, between 0.20 and 273.85 mg/L in the improved water sources, and between 0.70 and 12.88 mg/L in the water storage containers. The highest turbidity in improved water sources was recorded in protected springs in Mauche (273.85 mg/L), in unimproved sources was in river samples (94.53 mg/L), and in household containers was in jerry cans in Lare (12.88 mg/L) (Tables 4 and 5). Turbidity is a measure of light transmission through water which is influenced by the organic and inorganic particles suspended in the water (Muthuraman & Sasikala 2014). This parameter indicates microbial contamination as microorganisms prefer to attach to these particles (Yillia et al. 2008). The results from this assessment showed that turbidity levels in the majority of sources and container stored water were higher than the recommended WHO and KEBS guidelines (KEBS 2010; WHO 2011). High turbidity levels are caused by suspended and colloidal materials such as inorganic materials, clay, and silt (Juntunen et al. 2013; Perlman 2014). The high turbidity levels in various drinking water sources and water in household storage containers in this assessment indicated that the esthetic properties of the drinking water such as color and taste were greatly affected (Muthuraman & Sasikala 2014; Perlman 2014).

The measurements from this study for BOD varied between 0.17 and 1.82 mg/L in the unimproved water sources, between 0.17 and 1.94 mg/L in the improved water sources, and between 0.58 and 5.62 mg/L in the water storage containers (Tables 4 and 5). BOD is the amount of oxygen that is required to break down organic matter in water through aerobic processes by microorganisms (Razif & Persada 2015). Another study in the Njoro district to determine the extent of organic pollution of River Njoro reported that the 5-day BOD was in the range of 2.00 to 44 mg/L (Kiruki et al. 2011).

TDS in this study varied between 70 and 370 mg/L in the unimproved water sources, between 30 and 440 mg/L in the improved water sources, and between 10 and 260 mg/L in the water storage containers (Tables 4 and 5). The TDS levels were within the WHO and KEBS guidelines of 600 and 1,200 mg/L, respectively. TDS impact on the palatability of drinking water and constitute the dissolved inorganic anions and cations in water. High TDS is caused by sewage spillage, runoffs, chemicals used in water treatment, and the nature of materials used in the piping systems of drinking water (Ahmad & Chand 2015).

CONCLUSIONS

The quality of drinking water available to communities must be of a prescribed recommendation standard for physico-chemical quality. This study showed a variation in parameters tested across sampling points and between different water source types and between different storage container types. Although this study only undertook a one-off assessment of available water sources and water from household storage containers in a specific region in Kenya, the results from this study add to the growing set of data available for quality assessment on water used for domestic purposes in Kenya. The high levels of turbidity, iron, fluoride, manganese, and nitrate detected in the drinking water sample is worrying and a potential health risk to vulnerable individuals. Therefore, more frequent monitoring is needed to investigate specific contributing sources of pollution to water sources and household stored water. In order to achieve universal drinking water access for all by 2030, people must take ownership of their water sources and how they store water at the household level. There should also be adequate training of communities on water storage, handling, and treatment to ensure improvement in water quality in Njoro sub-county.

ACKNOWLEDGEMENTS

The authors are grateful to the Wellcome Trust SNOWS (Scientists Networked for Outcomes in Water and Sanitation) for funding this research project; Egerton University for providing the analytical equipment for the study and Dr Jacktone Othira (deceased) for valuable contributions during the study. Philip Kirianki, Edward Muchiri, and Natasha Potgieter conceived and designed the experiments; Philip Kirianki performed the experiments; Philip Kirianki and Natasha Potgieter wrote the paper and analyzed the data; Natasha Potgieter was the project leader. The authors declare no conflict of interest.

REFERENCES

REFERENCES
Ahmad
M.
&
Chand
S.
2015
Spatial distribution of TDS in drinking water of tehsil Jampur using ordinary and Bayesian Kriging
.
Pakistan Journal of Statistics and Operation Research
11
(
3
),
377
386
.
doi: http://dx.doi.org/10.18187/pjsor.v11i3.894.
Anake
W. U.
,
Benson
N. U.
,
Akinsiku
A. A.
,
Ehi-Eromosele
C. O.
&
Adeniyi
I. O.
2014
Assessment of trace metals in drinking water and groundwater sources in Ota, Nigeria
.
International Journal of Scientific and Research Publications
4
(
5
),
1
4
.
APHA
1998
Standard Methods for the Examination of Water and Wastewater
.
American Public Health Association
,
Washington, DC
.
Bouchard
M. F.
,
Sauvé
S.
,
Barbeau
B.
,
Legrand
M.
,
Brodeur
M. È.
,
Bouffard
T.
&
Mergler
D.
2011
Intellectual impairment in school-age children exposed to manganese from drinking water
.
Environmental Health Perspectives
119
(
1
),
138
143
.
Donde
O. M.
,
Muia
A. W.
&
Shivoga
A. W.
2013
Temporal variation in densities of microbiological indicators of pollution in water sources within Naivasha Lake basin, Kenya
.
International Journal of Scientific Research
2
(
10
),
131
138
.
Juntunen
P.
,
Liukkonen
M.
,
Lehtola
M. J.
&
Hiltunen
Y.
2013
Dynamic soft sensors for detecting factors affecting turbidity in drinking water
.
Journal of Hydroinformatics
15
(
2
),
416
426
.
doi: 10.2166/hydro.2012.052
.
Kalungu
J. W.
,
Filho
W. L.
,
Mbuge
D. O.
&
Cheruiyot
H. K.
2014
Assessing the impact of rainwater harvesting technology as adaptation strategy for rural communities in Makueni County, Kenya
. In:
Handbook of Climate Change Adaptation
(
Filho
W. L.
, ed.).
Springer Verlag
,
Berlin and Heidelberg
, pp.
1
17
.
doi: 10.1007/978-3-642-40455-9_23-1
.
KEBS
2010
KS05-459-1: 2007: Drinking water. Specification part 1; the requirements for drinking water (ICS 13.060.20), 3rd edn. KBS, Nairobi
.
Kenya National Bureau of Survey (KNSB)
2013
.
Khazenzi
J. A.
,
Osano
O.
,
Wakhisi
J.
&
Raburu
P.
2014
Risk among consumers of nitrate contaminated groundwater in Langas, Eldoret, Kenya
.
Baraton Interdisciplinary Research Journal
3
(
2
),
41
50
.
Kiruki
S.
,
Limo
M.
,
Mwaniki
N.
&
Okemo
P.
2011
Bacteriological quality and diarrhoeagenic pathogens on River Njoro and Nakuru Municipal water, Kenya
.
International Journal of Biotechnology and Molecular Biology Research
2
(
9
),
150
162
.
Maghanga
J. K.
,
Kituyi
J. L.
,
Kisinyo
P. O.
&
Ng'etich
W. K.
2012
Impact of nitrogen fertilizer applications on surface water nitrate levels within a Kenyan tea plantation
.
Journal of Chemistry
.
Article ID 196516, http://dx.doi.org/10.1155/2013/196516.
Mainuri
Z. G.
&
Owino
J. O.
2013
Effects of land use and management on aggregate stability and hydraulic conductivity of soils within River Njoro Watershed in Kenya
.
International Soil and Water Conservation Research
1
(
2
),
80
87
.
http://dx.doi.org/10.1016/S2095-6339(15)30042-3.
Meenaksi
A.
&
Maheshwari
R. C.
2006
Fluoride in drinking water and its removal
.
Journal of Hazardous Materials
137
(
1
),
456
463
.
doi: 10.1016/j.jhazmat.2006.02.024
.
Morrison
G.
,
Fatoki
O. S.
,
Persson
L.
&
Ekberg
A.
2001
Assessment of the impact of point source pollution from the Keiskammahoek Sewage Treatment Plant on the Keiskamma River-pH, electrical conductivity, oxygen-demanding substance (COD) and nutrients
.
Water Sabinet Africa
27
(
4
),
475
480
.
Moturi
W. K.
,
Tole
M. P.
&
Davies
T. C.
2002
The contribution of drinking water towards dental fluorosis: a case study of Njoro Division, Nakuru District, Kenya
.
Environmental Geochemistry and Health
24
(
2
),
123
130
.
doi: 10.1023/A:1014204700612
.
Munoz
R. C.
,
Calderon
R. P.
,
Flores
R. C.
,
Masangcap
S. C.
&
Angeles
J. P.
2015
Utilization of sensors and SMS technology to remotely maintain the level of dissolved oxygen, salinity and temperature of fishponds
. In:
Resource Enhancement and Sustainable Aquaculture Practices in Southeast Asia: Challenges in Responsible Production of Aquatic Species: Proceedings of the International Workshop on Resource Enhancement and Sustainable Aquaculture Practices in Southeast Asia (RESA)
, pp.
243
249
.
Muthuraman
G.
&
Sasikala
S.
2014
Removal of turbidity from drinking water using natural coagulants
.
Journal of Industrial and Engineering Chemistry
20
(
4
),
1727
1731
.
doi: 10.1016/j.jiec.2013.08.023
.
Mwaura
F.
2003
The spatio-temporal characteristics of water transparency and temperature in shallow reservoirs in Kenya
.
Lakes and Reservoirs: Research and Management
8
,
259
268
.
doi: 10.1111/j.1440-1770.2003.00226.x
.
Njenga
L. W.
,
Kariuki
D. N.
&
Ndegwa
S. M.
2005
Water-labile fluoride in fresh raw vegetable juices from markets in Nairobi, Kenya
.
Journal of International Society for Fluoride Research
38
(
3
),
205
208
.
Perlman
H.
2014
Water properties and measurements. In: USGS Water Science. Available at: http://water.usgs.gov/edu/turbidity.html (accessed January 2016)
.
Razif
M.
&
Persada
S. F.
2015
The fluctuation impacts of BOD, COD and TSS in Surabaya's rivers to environmental impact assessment (EIA) sustainability on drinking water treatment plant in Surabaya City
.
International Journal of ChemTech Research
8
(
8
),
143
151
.
Shadrack
M. K.
2012
Effects of sediment loads on water quality within the Nairobi River Basins, Kenya
.
International Journal of Environmental Protection
2
(
6
),
16
20
.
Shivoga
W. A.
,
Muchiri
M.
,
Kibichi
S.
,
Odanga
J.
,
Miller
S. N.
,
Baldyga
T. J.
,
Enanga
E. M.
&
Gichaba
M.
2007
Influences of land use/cover on water quality in the upper and middle reaches of river Njoro, Kenya
.
Lakes and Reservoirs: Research and Management
12
,
79
105
.
doi: 10.1111/j.1440-1770.2007.00325.x
.
Wendt
A.
,
Waid
J.
&
Gabrysch
S.
2016
Perceived iron content in drinking water associated with anemia among women with iron-poor diets in rural Bangladesh
.
The FASEB Journal
30
(
1
),
892
891
.
WHO
2011
Guidelines for Drinking-Water Quality
,
4th edn
.
World Health Organization
,
Geneva
. .
Yillia
P. T.
,
Mathooko
J. M.
&
Ndomahina
E. T.
2008
The effect of in-stream activities on the Njoro river, Kenya. Part II: Microbial water quality
.
Physics and Chemistry of the Earth
33
,
729
737
.