WATER TREATMENT In Industries Water is used for: a. Drinking b. Cleaning c. Cooling d. Producing Steam e. Process requirement Why we need to treat water? For human consumption a. Water to be purified (Make it free of Bacteria) b. De-chlorinated c. Suspended solids are removed Water supplied by M/s Marafiq is fit for drinking purposes. Then, why do we need to treat water? Water supplied by Marafiq does not meet the process requirements. Boiler requires high pure water free of Hardness and gases to avoid scaling and corrosion Process unit requires stringent quality water to avoid corrosion of process equipments Water Contaminants Dissolved gases such as O2, CO2, SO2, NH3 Dissolved salts such as Carbonates, Chlorides Insoluble matters like dust, sand, clay 1
Raw water Quality ph 8.0-8.5 Hardness 25-60 ppm Total Suspended Solids 0 ppm Total Dissolved Solids 40-80 ppm Chlorides 5-25 ppm Sulphates 5 25 ppm Silica (SiO2) 0 1 ppm Impurities ph-indicates the nature of material whether it is Acidic, Alkaline or Neutral ph < 7 is Acidic ph = 7 is Neutral Ph > 7 is Alkaline Preferred ph is 6.5 to 8 Hardness: It indicates the presence of Calcium and Magnesium salts along with Iron, Aluminum and Manganese in small quantities. Eg: Calcium carbonate, Magnesium carbonate Carbonates tend to form scales on the surface. These scales reduce the heat transfer and also results in corrosion of the surfaces. Total suspended solid (TSS) The matter which is insoluble in water and remains in suspension. Eg. Dust, Sand, Clay, Algae Suspended solids will tend to plug the pipes and also form scales Total dissolved solid (TDS) Salts which are soluble in water and cannot be removed by filtration. Eg: Chlorides, Silicates At high temperature they precipitate and form scales on the surface. 2
Water Quality required for Process and Boiler PH 7.0-9.0 Hardness Nil Total Suspended Solids 0 ppm Total Dissolved Solids 7 ppm (max) Chlorides 5 ppm (max) Silica 0.5 ppm (max) Water can be treated by De-mineralizing water using Ion exchange Resins Reverse Osmosis process What is Osmosis? If a dilute solution is separated from a concentrated solution by a semi permeable membrane, pure solvent flows from the dilute solution to the concentrated solution through the membrane. This is called Osmosis. Why it is Reverse Osmosis? If pressure is applied more than the Osmotic pressure of the concentrated solution, then pure solvent will flow from concentrated solution to dilute solution. This is called Reverse Osmosis. Reverse Osmosis system consists of: Multi grade filter Activated carbon filter Anti-scalant dosing system Cartridge filter High pressure pump RO assembly 3
Osmosis Treatment Pure water out Membrane Filter Water IN High Pressure pump Micron filter Reverse Osmosis Water inlet Activated carbon filters Cartridge filter RO assembly Water inlet HP pump Water storage tank RO reject Multi grade filters Anti-sealant dosing Effluent Drain 4
Multi Grade Filters Purpose: To remove TSS Consist of different grades of sand, gravels and pebbles. Raw water from the tank is pumped through series of multi grade filters to remove all suspended solids. Activated Carbon Filters Purpose: To remove of Chlorine and left over organism Filter packs filled with activated carbon material. After removal of suspended solids, water is sent through activated carbon filter to remove residual chlorine and left over organism. Micron Cartridge Filter Purpose: To remove fine particles Filter element with 5 micron stainless steel material cloth. After passing through activated carbon filters, feed water enters into micron cartridge filters in order to remove very fine particles which are not removed by multi grade filters. Anti-Scalant Dosing Purpose: To avoid scaling on the membranes Anti-scalant is the chemical which is injected using dosing pumps This is to avoid silica or calcium carbonate scaling of the membranes What is Membrane? Membrane is a thin material that separates two environments Membrane is made out of tiny tissue material either from plants or fiber. 5
6 1 micron = 1/1000 mm
RO system When the raw water (concentrated solution) is pumped to RO system membrane at high pressure, pure water (dilute solution) flows to the other side of the membrane. The pure water is removed continuously. The dissolved solids rejected by the membrane concentrate and are flushed out continuously. RO system The unit is designed to produce RO water at 5 M3/Hr flow. 75% of water is recovered as pure water 25% is rejected and goes to effluent system. 7