OCHIENG S. SYLVESTER E25-0112/04

Bsc. CIVIL, CONSTRUCTION AND ENVIRONMENTAL

ENGINEERING.

SUPERVISOR: DR. THUMBI

INTRODUCTION

BACKGROUND

Point and non-point source pollution due to degraded water quality

and altered hydrography among others, have been recorded among

streams and rivers draining urban areas. Large quantities of liquid,

solid and sewage wastes find their way into the rivers. Fish species

are becoming endangered and water supplies become scarce and

polluted.

PROBLEM JUSTIFICATION.

Only a very small quantity of the Earth’s fresh water, around 0.008

per cent, is available for human use. 70% goes to agriculture, 23% to

industry, and only 8% to domestic consumption. In developing

countries, 95% of human waste water is discharged untreated or

minimally treated into water bodies.

PROBLEM STATEMENT. Population growth in the country and in particular Ruiru town has

sharply increased the demand for potable freshwater.

Pollution along River Ruiru is at critical levels. If cleanup was carried

out on the river, it would add to the water sources for domestic use.

RESEARCH OBJECTIVES.

Main objective:

The main objective is to evaluate the pollution profile of River Ruiru as it flows through Ruiru town.

Specific objectives

To evaluate the organic levels at different points along the river.

To determine the effluent discharge points from Ruiru town.

RESEARCH HYPOTHESIS

Most Rivers flowing through urban centers get polluted by wastes,

based on that fact, it is therefore hypothesized that River Ruiru is

polluted as it flows through Ruiru town.

STUDY LIMITATIONS.

The research will be limited to selected points along the river

due to limited time assigned to the project.

Due to limited Financing, only selected areas can be studied

and as such an extensive study of the whole river is not possible.

LITERATURE REVIEW

TYPES OF POLLUTANTS (K. V. Ellis, 1989).

Sewage and other oxygen-demanding wastes

Pesticides and herbicides

Pathogens

Inorganic minerals and chemical compounds

Sediments washed by storm water

Radioactive substances

SOURCES OF POLLUTANTS (Wandiga, S., 1999).

Municipal

Industrial wastes

Agricultural wastes

Storm water.

EFFECTS OF WATER POLLUTION (K. V. Ellis, 1989).

Notable effects of water pollution include those involved in:

Human health.

Acid rain

Eutrophication

SELF-PURIFICATION OF STREAMS (K. V. Ellis, 1989).

Factors influencing self-purification: Dissolved oxygen Type of organic matter Toxic substances Physical characteristics of the stream Weather conditions Dilution Sedimentation and sludge deposits

DESCRIPTON OF SOME PARAMETERS (K. V. Ellis, 1989).

Hydrogen ion concentration or pH

Temperature Chemical Oxygen Demand (COD) Dissolved Oxygen Ammonia

RESEARCH METHODOLOGY

STUDY AREA

The study area encompasses the entire length of the river as it

flows through Ruiru town. The samples are to be taken at the

river’s entry into the town, at two intermediate points and at the

exit.

SAMPLING

A total of four sampling points were chosen based on;

Accessibility of the sampling points, cost effectiveness for

collection, analysis and reporting. The assumption here is that the

river is not highly polluted as it enters the town, it gets polluted in

the town and thus its pollution load should be greater in the town.

STUDY AREA

PARAMETERS ANALYZED

TEMPERATURE

The temperature is to be monitored on-site at the time of sampling.

CHEMICAL OXYGEN DEMAND (COD)

This is to be determined using the open reflux method. It is used as a measure of

the oxygen equivalent of the organic matter content of a sample susceptible to

oxidation by a strong chemical oxidant.

DISSOLVED OXYGEN (DO)

It is determined using the titration method and is required to support aquatic life.

pH (pH METER METHOD)

The test is carried out using a pH meter dipped in the sample.

AMMONIA TEST (DPD METHOD)

Done using a photometer set to 640nm.

RESULTS

Date Sampling

station

Temperature

(oC)

Hydrogen ion

concentration

Mg/L

Dissolved

Oxygen

Mg/L

Chemical

Oxygen

Demand mg/L

Ammonia

Mg/L

4TH NOV 1

2

3

4

24

24

23

24

7.06

6.65

6.56

6.83

4.1

3.6

2.5

2.1

180

200

205

258

0.63

0.86

0.96

1.05

12TH NOV 1

2

3

4

22

23

23

22

8.57

8.36

8.23

7.53

3.8

3.4

3.2

2.6

208

225

238

249

0.76

0.92

1.15

1.25

19TH NOV

(wet day/

period)

1

2

3

4

22

22.5

22

23

8.73

8.33

7.85

7.56

4.4

4.1

3.6

3.3

155

185

188

203

0.55

0.59

0.67

0.78

19TH JAN 1

2

3

4

24

23

24

24

8.65

8.32

7.22

6.85

3.8

3.6

3.2

2.5

210

212

227

245

0.65

0.77

0.98

1.22

27TH JAN 1

2

3

4

24

23

24

23

8.63

8.26

7.96

7.65

3.6

3.5

2.8

2.3

198

255

268

305

0.83

0.96

1.23

1.26

9TH FEB 1

2

3

4

22.5

23

23

24

7.98

7.86

7.21

7.08

3.7

3.2

2.6

2.1

225

248

285

335

0.85

0.98

1.28

1.33

TEMPERATURE

CHEMICAL OXYGEN DEMAND

Temperature variations showing

lower values on the wet day and

higher values on the dryer days.

Temperature values lie within the

recommended values, thus no

evidence of thermal pollution

COD levels noted to increase as the

river progresses towards the town’s

exit.

AMMONIA

AVERAGES

Ammonia values on the

increase as the river progresses

towards the town’s exit.

The average values of the

parameters tested show

progressive increases in the

COD and Ammonia and

decreases in the pH and DO.

HYDROGEN ION CONCENTRATION

DISSOLVED OXYGEN

The hydrogen ion concentration showing the values lie within the recommended range of 6.5-8.5

The DO values showing a progressive decrease in the values from the initial to the final station.

Parameter Guide value

(maximum

allowable limit)

Station 1 Station 2 Station 3 Station 4

Ph 6.5 – 8.5 8.27 7.96 7.51 7.25

Ammonia 0.5 (mg/L) 0.71(mg/L) 0.85(mg/L) 1.05(mg/L) 1.15(mg/L)

DO 5.0 mg/L 3.9(mg/L) 3.6 (mg/L) 3.0(mg/L) 2.5(mg/L)

COD 50 (mg/L) 196(mg/L) 221(mg/L) 235(mg/L) 266(mg/L)

KENYA STANDARDS

WORLD HEALTH ORGANIZATION STANDARDS

Parameter Guide value

(maximum

allowable limit)

Station 1 Station 2 Station 3 Station 4

pH 6.5 - 8.5 8.27 7.96 7.51 7.25

Ammonia 0.2 mg/l (up to 0.3

mg/l in anaerobic

waters)

0.71(mg/L) 0.85(mg/L) 1.05(mg/L) 1.15(mg/L)

DO 5.0 mg/L

about 75%

saturation

3.9(mg/L) 3.6(mg/L) 3.0(mg/L) 2.5(mg/L)

COD 50(mg/L) 196(mg/L) 221(mg/L) 235(mg/L) 266(mg/L)

CONCLUSION The pollution monitoring of the Ruiru River has led to the following conclusions after analysis of the data obtained: • The field investigations coupled with laboratory analysis of

samples obtained from 4 monitoring stations from Ruiru River confirmed gross pollution of the River. Most pollutants in the river exceed accepted discharge standards into natural rivers.

• The Ruiru River pollution increases as the river flows progressively downwards. The upstream section shows lesser pollution, followed by the middle section and the downstream section showing the highest pollution load. This area is characterized by solid waste and the water has a characteristic odour which is strong and pungent. This is an indication of high microbial activity (anaerobic) giving up a lot of gases.

RECOMMENDATIONS

The following are some of the measures that need to be taken:

Clean up action plan be drawn up and to involve communities living and

operating along the Ruiru River.

The discharge of human waste into the river should be addressed.

The industrial discharges should be stopped through efforts by the industries

to take measures to address pollution emanating from their production

processes.

Some technical and financial support should be considered in developing

technologies to pre-treat discharges from industries.

There is need, to look at the existing legislation in relation to environmental

pollution, penalties and enforcement.

Continue to build the capacity of the Local Authorities through

improvement of the monitoring laboratories and equipment as well as

organizing refresher courses.

Continuous monitoring of the river to ascertain that the pollution

levels are within recommended levels.

Engineering solutions to clean up efforts such as channeling,

introduction of flow weirs in the river in order to increase the flow

conditions, especially on the stagnant sections of the river to enhance

the river self-purification and increase oxygen dissolution.

A vigorous campaign to educate people on the importance of a clean

environment and the danger of polluted waters should be initiated

immediately.