Water Quality Lab
Introduction: In this lab, temperature, pH, turbidity and dissolved oxygen are measured using water from
the Chao Phraya river in Thailand.
Temperature is a measure of the average kinetic energy of the particles in a sample of matter
expressed in terms of units or degrees designated on a standard scale with a thermometer. There are many
factors that can affect water temperature. Thermalpollution caused by human activities, due to industries
using river water in the processes is an example. Another factor that can affect water temperature is the
temperature of the air above the water. There are many factors that can take part in warming the water
surface but not many that cause it to be cooled. However,a way that can be cooled is by cold air
temperatures or from the introduction of colder water from a tributary or a spring. Other factors include:
air temperature, amount of shade, soil erosion increasing turbidity, thermal pollution from human
activities and confluence of steams.
pH is the measure of the acidity or of a solution Water has both hydrogen ions, H+
The concentration of these ions determines the pH value. Water that has a pH of 7 has
equivalent concentrations of the two ions and is considered to be a neutral solution. If a solution is acidic,
the concentration of the H+
ions surpasses that of the OH−
ions. The concentration of OH−
that of H+
ions. On a pH scale of 0 to 14, 0 is the most acidic and 14 is the most basic. Factors that affect
pH are acidic rainfall, algal blooms, the level of hard-water minerals, releases from industrial processes,
carbonic acid from respiration or decomposition and oxidation of sulfides in sediments. It is numerically
equal to 7 for neutral solutions, increasing with increasing alkalinity and decreasing with increasing
acidity. It is measured either with a pH probe or pH strips.
Turbidity is a measure of water’s lack of clarity. Water that is cloudy has high turbidity
while water that is clear has low turbidity. Cloudiness in water comes from light reflecting off of particles
in the water; therefore,that more particles that are in the water, the higher the turbidity is. There are
different factors that take part in the turbidity of water:soil erosion, urban runoff, industrial waste,
abundant bottom-dwellers and organics. The effects or turbidity are that it reduces water clarity, it is
aesthetically displeasing, it decreases photosynthetic rate and increases water temperature. A secchidisk
is used to measure turbidity and is measured in Nephelometric Turbidity Units (NTU). The turbidity of
surface water is usually between 1 NTU and 50 NTU.
Dissolved oxygen (DO) is the amount of oxygen measured in the water. Sources of DO include
diffusion from the atmosphere, aeration as water moves over rocks and debris, aeration from wind and
waves,photosynthesis of aquatic plants. Factors that affect DO are temperatures,aquatic plant
populations decaying organic material in water,stream flow, altitude/atmospheric pressure,human
activities. DO is expressed in mg/l or as percent saturation. It is measured with a DO kit.
The water samples came from the Chao Phraya river in Thailand which covers 160,000km (30%
of the country's total area). This river begins in Nakhon Sawan and flows north to south for 372km from
the centralpains to Bangkok and the Gulf of Thailand. The river splits in Chainat to the direct river line.
The Tha Chin river, which then runs parallel to the direct river and terminates towards the Gulf of
Thailand about 35km west of Bangkok. Below the Chainat dam, there are many little canals that break-off
from the main river. These canals are used for the irrigation of the local rice paddies. It was noticed that
the water quality was low due to sewage and human waste. It has been noted by the National
Environmental Board, the Pollution Control Department and the Ministry of Public Health that the water
in the Lower basin has heavy organic and bacterial pollution in the Chao Phraya.
Research Question: How does land use affect water quality?
Variables: The independent variable is the land use. The dependent variable is the temperature,pH,
turbidity and dissolved oxygen. The control group is the source of measurement as well as the fact that all
the tests were done on the same day.
Water from the Chao Phraya river
1. Collect a sample of water from the residential area.
2. Put a thermometer into the sample of water and record the temperature.
3. Put the pH strips into the water and record it.
4. Use a Secchidisk and to find the turbidity.
5. Test the dissolved oxygen (refer to the DO test kit).
6. Collect a sample of water from the rural area.
7. Repeat steps 2 to 6 with the water from the rural area.
8. Get a sample of water from the commercial area.
9. Repeat steps 2 to 6 with the water from the commercial area.
*Refer to all calculations below the tables.
Table 1: the raw data results from the temperature,pH (average),turbidity and dissolved oxygen tests.
Residential Area Rural Area Commercial Area
Temperature 28 28 28
pH (average) 6 7 6
Turbidity 0.54 (8.85 NTU) 0.47 (7.71 NTU) 0.65 (10.66 NTU)
Dissolved Oxygen 4ml/L (50%) 2ml/L (23%) 2.5ml/L (30%)
Q-Value →Table 2: the Q-Value results from the temperature, pH (average),turbidity and dissolved
Residential Area Rural Area Commercial Area Weighting
Temperature 93 93 93 0.1
pH (average) 55 89 55 0.11
Turbidity 79 83 76 0.08
Dissolved Oxygen 45 15 20 0.17
Table 3: the total results for the temperature,pH (average),turbidity and dissolved oxygen tests.
TOTAL Residential Area Rural Area Commercial Area
Temperature 9.3 9.3 9.3
pH (average) 6.05 9.79 6.05
Turbidity 6.32 6.64 6.08
Dissolved Oxygen 7.65 2.55 3.4
WQI for Residential Area: 64 which is qualified as medium/average water.
WQI for Rural Area: 61 which is also qualified as fair water.
WQI for Commercial Area: 54 which is also qualified as fair water.
Turbidity of residential land use: 0.762/0.54 = 12.5/x
0.762x = 6.72
x = 8.85 NTU
Turbidity of rural land use: 0.762/0.47 = 12.5/x
0.762x = 5.875
x = 7.75 NTU
Turbidity of commercial land use: 0.762/0.65 = 12.5/x
0.762x = 8.125
x = 10.66 NTU
Weight factor of temperature:0.1
Rural + Residential + Commercial = 93 x 0.1 = 9.3
Weight factor of pH: 0.11
Residential + Commercial = 55 x 0.11 = 6.05
Rural = 89 x 0.11 = 9.79
Weight factor of dissolved oxygen:0.17
Residential: 45 x 0.17 = 7.65
Rural: 15 x 0.17 = 2.55
Commercial: 20 x 0.17 = 3.4
Weight factor of turbidity: 0.08
Residential: 77 x 0.08 = 6.16
Rural: 80 x 0.8 = 6.4
Commercial: 74 x 0.08 = 5.92
Data Processing & Presentation:
Graph 1: the raw data results from the dissolved oxygen, turbidity, pH average and temperature tests.
Conclusion: The temperatures for the residential, rural and commercial areas were allthe same—28ºC.
The pH for the residential and commercial were 6 while the rural pH was 7. The lowest turbidity was for
the rural area,at 0.47 meters (7.71 NTU). The turbidity for the residential area was 0.54m (8.85 NTU)
and the commercial area the highest with 0.65m (10.66 NTU). The dissolved oxygen was 2ml/L (23%)
for rural, 2.5ml/L (30%) for commercial and 4ml/L (50%) for residential.
Evaluation: One of the benefits in this experiment was that all the tests were done on the same day. Had
the tests been timed better with a stopwatch, maybe the results would have been more accurate and more
consistent. All the materials that were needed for the tests were collected a few days before the actual
experiment. This had its advantages and disadvantages. By being prepared early enough, there was little
stress,yet, there was less ‘double checking’ done. Luckily, this didn’t affect the experiment that was done
because all the necessary materials were there. Another disadvantage was the lack of controlled time.
Next time, the time span should be clarified better so that enough time is given for each part of the
0 5 10 15 20 25 30
Dissolved Oxygen (percent