WASTEWATER TREATMENT

A drop of hazardous substance can be enough to pollute thousands of gallons of water, so it is vitally important to accurately and efficiently control chemicals that endanger the environment and human health. (EU environment commissioner)

Wastewater treatment is the process of removing contaminants from wastewater and household sewage, both runoff (effluents), domestic, commercial and institutional. Its objective is to improve water quality in order to be suitable for disposal without causing any prejudice to flora or fauna. GENERAL INFORMATION The final products of wastewater treatment are purified water and sludge.

The first step in treatment is wastewater collection which is made by sewers. Water leaking from various sources, polluted compared to their initial state, are called waste water. Wastewater is treated in wastewater treatment plants. WASTEWATER

The main harmful substances of industrial wastewater are: Organic substances Substances in suspension Toxic substances Heavy metals The most massive and harmful pollution category is represented by the pollution of industrial wastewater.

2. Grids retain high dirt like branches or wires and the smallest ones are retained by sieves. 1. Gravity separation of heavy particles, undissolved in water, under the influence of gravity, through sedimentation or centrifuging. PHYSICAL PROCESSES OF TREATMENT

Chemical treatment of wastewater is carried out by methods of neutralization, oxidation and reduction, ion exchange or by the use of catalysts that accelerate the chemical reactions. By chemical treatment process, contaminants are either removed, either converted into more easily separable substances with a reduced harmful activity. CHEMICAL TREATMENT PROCESSES

The transfer between the phases is based on the passage of pollutants in another phase, immiscible with water, which may be liquid, solid or gas. Membrane water treatment is called osmosis. The membrane is a barrier to molecular or ionic species in water. MEMBRANE WATER TREATMENT

A transfer of materials from water to living cells and from these to water is being realized. Biological treatment is a finishing step of treatment and can achieve high efficiency. Through biological treatment organic contaminants are transformed in harmless degradation products and biomass. BIOLOGICAL TREATMENT

Biological treatment consists of two processes: 1. Aerobic biological process involving microorganisms that require dissolved oxygen to carry out metabolic processes; 2. Anaerobic biological process involving microorganisms that use the oxygen of organic matter or mineral compounds.

Ion exchangers are used in water treatment by softening, elimination of carbonates, deionization, the removal of organic substances. TREATMENT WITH ION EXCHANGE Treatment with ion exchange resins is particularly applicable to the removal of ions of iron, manganese, zinc, copper, present in high concentrations.

CATALYTIC TREATMENT Catalytic purification is based on the chemical conversion of organic and inorganic pollutants in the presence of catalysts which accelerate the role of chemical reaction. The method has a limited application because either the catalyst is not active in all cases, either the products of oxidation are very harmful substances (e.g. chloride acid, phosgene).

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