Understanding the SRNL Data Set

Water from the lake was collected in sterile containers monthly from August 2014 to July, 2015 and transported in a cold chamber to the Laboratory of the Technology Incubation Centre, Federal Ministry of Science and Technology, Nnewi, for Physico-chemical and biological analysis using the method described by the American Public health Association (APHA) (2000).

a. pH

Using a pH meter (Model 23A direct-reading pH meter), the pH of the water was measured by dipping the pH meter into the water body and the measurement taken.

b. Conductivity (uS/cm)

Conductivity was measured using a conductivity meter (conductometer- HANNA Instruments, Model DiST 1, Rhode Island USA). The water sample was poured into a glass dish. The red and black lead of the multimeter was plugged into its positive and negative ports respectively. The multimeter was turned on and its measurement dial switched to the resistance setting. The leads were touched to the water at opposite ends of the longest dimension of the glass dish. The resistance in ohms that appeared on the screen was noted. The length, width and depth of the glass dish were measured in centimeters. The width was multiplied by the depth to obtain the area of the sides of the glass dish in square centimeters. The length was divided by the product of the resistance and the area to arrive at the conductivity in units of siemens/meter. The conductivity was converted to microsiemens/cm by multiplying by 10,000.

c. Total Dissolved Solids (TDS) (mg/l)

An empty evaporating dish that has been dried at 180⁰C for an hour was weighed and 100 ml of sample was well mixed and poured into a funnel with filter paper, then 75 ml of unfiltered sample was transferred into a porcelain dish. The oven was switched on and allowed to reach 105⁰C. The dish was placed in the oven and dried for about 2hours; it was cooled in the

52 desiccator. Weighing and drying of the dish was continued until a constant weight was reached. The difference in the initial and final weight gives the TDS (mg/l).

d. Total Hardness (mg/l)

The total hardness of the water was measured using Varian AA240 Atomic Absorption Spectrophotometer. Fifty mililitres (50 ml) of the water was measured into an opaque white container. The pH of the water sample was adjusted from the acidic pH which it was to 7-10 by adding Ammonium hydroxide (NH4OH) and Hydrochloric acid (HCl) solutions. Then 0.5ml of buffer solution was added with 0.2g of hardness indicator powder was added and the mixture was stirred. Standard Disodium Hydrogen Ethylene Dialene Tetraacetic Acid (Na2H2EDTA) solution was added slowly from a burette with continuous stirring. The titration was completed within five minutes after addition of the buffer and the colour changed from red to blue which is the end piont was noted and measurement taken.

The total hardness of the water was calculated as:

Total Hardness (mg/l) = titre value x 1000/volume of sample used.

e. Calcium Hardness (mg/l)

Fifty mililitres (50ml) of the water sample was measured into an opaque white container, 2mls of Sodium hydroxide solution and 63-Hydroxy-4(2-hydroxy-4 sulfo-Inaphthy 1) azo-2,7, naphthalenedisulfonic acid, trisodium salt were added and stirred. Again 0.2g of Calcium indicator was added and stirred. Standard Na2H2EDTA solution was added slowly from a burette and stirred continuously. The titration was completed within five minutes after addition of the buffer and the colour change from red to royal blue which is the end piont was noted and measurement taken.

The Calcium hardness of the water was calculated as:

Calcium Hardness (mg/l) = titre value x 1000/volume of sample used.

53 f. Magnesium Hardness (mg/l)

50ml of the water sample was measured into an opaque white container. Then 2mls of Sodium hydroxide solution and 63-Hydroxy-4(2-hydroxy-4 sulfo-Inaphthy 1) azo-2,7, naphthalenedisulfonic acid, trisodium salt were added and stirred. Again 0.2g of Magnesium indicator was added and stirred. Standard Na2H2EDTA solution was added slowly from a burette and stirred continuously. The titration was completed within 5mins after addition of the buffer and the colour change from red to royal blue which is the end piont was noted and measurement taken.

The Magnesium hardness (mg/l) of the water was calculated as:

Magnesium Hardness (mg/l) = titre value x 1000/volume of sample used.

g. Nitrite concentration (mg/l)

Nitrite concentration of the water was determined using PD303 UV Spectrophotometer. Fifty mililitres (50ml) of the water sample was pipetted into a porcelain dish and evaporated to dryness on a hot water bath. Then 2ml of Phenol disulphonic acid was added to dissolve the residue by constant stirring with a glass rod, then 2mls of concentrated solution of Sodium hydroxide, 5ml of 1molar zinc sulphate and distilled water were added with stirring to make it alkaline. This was filtered into a Nessler’s tube and made up to 50ml with distilled water.

The absorbance was read spectrophotometrically at 410nm after colour development.

h. Nitrate concentration (mg/l)

Nitrate concentration of the water was determined using PD303 UV Spectrophotometer. Fifty mililitres (50ml) of the water sample was pipetted into a porcelain dish and evaporated to dryness on a hot water bath. Then 2ml of Phenol disulphonic acid was added to dissolve the residue by constant stirring with a glass rod. After, 2mls of concentrated solution of Sodium hydroxide and distilled water weres added with stirring to make it alkaline. This was filtered into a Nessler’s tube and made up to 50ml with distilled water. The absorbance was read spectrophotometrically at 410nm after colour development.

54 3.8 Biological Analysis of the Lakes within the study period

a. Total coliform (MPN/100ml)

The spread plate method was used (APHA, 2000). Nine millimeters of sterile normal saline solution was distributed in ten test tubes for serial dilution. The test tubes were sterilized by autoclaving at 121⁰C for 15 minutes after which 1ml of the water sample was transferred into the tube containing 9ml of normal saline using sterile pipette to make the ten fold serial dilution. The first tube gave 10^-1 dilution, subsequent ten fold serial dilutions were prepared up to 10^-10.

Using a sterile 1ml pipette, 0.1m from 10^-3 and 10^-4 dilution were transferred asceptically onto the surface of solid nutrient agar and MacConkey agar plates (Titan Biotech Ltd India).

Each dilution was plated in duplicate. The innoculum were evenly spread over the surface of the medium using sterile wire loop. The plates were then incubated at 37⁰C for 24hours. The colonies on each plate were counted and the colony forming units per ml of water samples were computed using its formular.

b. Faecal coliform (MPN/100ml)

Feacal coliform was enumerated using the most probable number technique. The test was performed using three columns of test tubes. This test was carried out in three stages. The three stages include presumptive, confirmatory and completed test stages.

Presumptive Test Stage Procedure

10ml of undiluted water sample was transferred into three tubes containing 10mls of double strength lactose broth. 1ml of the sample was inoculated into the tube containing 10ml of single strength lactose broth and 0.1ml of the sample which was diluted to 10^-1 was inoculated into tubes containing 10ml of single strength lactose broth. In each case, sterile inverted Durham tube was inserted and triplicate tubes were made. A control was used. The tubes were inoculated at 37⁰C for 24 hours and observed for gas production (which indicates the presence of faecal coliform in the water sample) in the Durham tubes. The total feacal counts from positive tubes were read.

55 Confirmatory Test Stage Procedure

Cultures from positive tubes from the presumptive tests were streaked into brilliant green lactose bile broth with the aid of a sterile wire loop and incubated at 37⁰C for 24 hours. The tubes were observed for colour change from purple to yellow (acid) and gas production in the inverted Durham tubes indicating confirmation of the presence of faecal coliform in the water sample.

Completed Test Stage Procedure

The feacal coliform colonies observed in the confirmed test were then transferred asceptically onto eosine – methylene blue (EMB) agar plates with the aid of a sterile wire loop. The plates were incubated at 37⁰C for 24hours and observed for growth of pink mucoid colonies with metallic sheen. Gram staining and spore staining were made with colonies from EMB plates.

Non-spore forming gram negative rods from the agar plate constituted the completed test for faecal coliforms.