Water Pollution

Introduction Water is the origin of life. Life found in the Earth is because of present of the water source such as marine, stream, lake,etc. however, we do not treasure it, producing serious problems on it. If the situations are not improved immediately, the consequence will be worse and worse. Therefore, water pollution should not be neglected and the situation should be aware by compensation.

Main resources

1) Effluents Cause: Released by industrial plants. Throw metal cans into the sea. Contain heavy metals ( e.g, Nickel, Mercury, lead, chromium and cyanide) Carcinogenic Fatal Usually treated before sewage, but still remains. NiCl 2 (a.q) + 2NaOH (a.q) → Ni(OH) 2 (S) +2NaCl (a.q) Cr 2 (SO 4 ) 3(a.q) + 2NaOH (a.q) → 2Cr(OH) 3(s) + 3Na 2 SO 4(a.q)

Solution Strict control by government. Qualified chemist to operate treatment Sewage into remote sea Regular up-date treatment equipment

2) Pesticides Kill insects To eliminate grass Mainly contain DDT Toxic non-biodegradable Soluble in fat

Effects During raining, flow into river or lake. Intake by small fish, eaten by larger one. Accumulate along the food chain. Damage internal organs. May lead to be infertile. Insect be resistant to it.

Possible Solution Avoid using it. Completely ban. Instead by other chemicals or method. In farm, can use other method. By your hand in the house.

3) Oil leakage Oil leakage would cause oil pollution on the marine. The main sources are: 1) damage to the oil tanker ships through collision with other ship, explosion or wrecking. 2)seepage from offshore installation. 3)flushing of tanker holds.

The effects caused by oil leakage The crude oil kills marine living things by suffocation.Destroys food chain It kills marine mammals, like fish-eating bird. The shading may restrict light penetration and reduce photosynthesis of marine plant. Destroys scenery

CLEAN-UP TECHNIQUES Aerial and Vessel spraying dispersant may be used for cleaning although those containing hydrocarbon solvents may be more effective with viscous oils because of their greater ability to penetrate into the oil.

Dispersants have two main components, a surfactant and a solvent. Surfactants are molecules which have an affinity for two distinct liquids which do not mix, acting as an interface between them. A part of the surfactant molecule used in dispersants has an attraction to oil (i.e. it is electrophilic) while another part has an attraction for water (i.e. it is hydrophilic).

4) Detergent Detergent is a cleaning agent which is needed to clean most of the dirt particles on our skin and clothes which contains the grease. However, it causes the serious water pollution in Hong Kong.

Non-biodegradable detergents Their carbon chain is not straight, have the branches The branches let it become non-biodegradable That mean they cannot be decomposed by bacteria in sewage treatment plants. The lather produced form the thick foam Foams kills water lives in river and sea

Biodegradable detergents They can be decomposed by bacteria,still cause problems Bacteria in water use up the oxygen to decompose the detergent Let bad smell Let the marine lives are lacking in oxygen Detergent often contain builders, which are phosphate salts

Phosphate are the nutrients of algae Algae then grow quickly,forming a thick layer Light can enter the deeper level of water Plant dies because of no photosynthesis

Solution Change non-biodegradable detergent to biodegradable detergent Removal of the detergent and phosphates in sewage treatment plants,but it is too expensive

5) Live stock waste Live stock wastes are mainly the waste from the farmland. The farmland which have some livestock will produce many wastes, like the feedstuff and excretion of the livestock. The owner will just eliminate this pollutant into the river without any further treatment

effects This waste will enhance the growth of algae. The increasing amount of algae will block the sunlight penetrate into water.Thus.the aquatic plants cannot undergo photosynthesis to produce food and release oxygen. This lead to the death to the aquatic plants then the aquatic organisms

solution To prevent this, a law should be set up to penalize the people who throw their live stock wastes into river without any treatment. Also,a sewage treatment fee is very important to control the people who produce extra wastes.

Water quality a.) Using Dissolved Oxygen ( DO) as indicator of oxygen. 1)measured as mass(mg) of oxygen per volume (dm 3 ) of water  mass / volume (mg dm -3 ) OR 2)measured as % saturation of oxygen.

b.) Using Biological Oxygen Demand (BOD) as an indicator of the extent of water pollution (means bacterial oxygen required) High BOD  more O 2 needed to break down organic matter  contain more organic matter. Natural water has a BOD = 1 – 4 mg dm -3 BOD 5 == the oxygen demand within five days called five-day DOB

conclusion If we still want to enjoy the beauty of the beach in holiday or eat the delicious sea foods. Then,stop contaminating the sea from now. This is not only your responsibility to stop doing so by yourselves,you should also tell this message to the one you know.