Water treatment process for membranes

An enhanced membrane process for the economical treatment and purification of ground water containing colloidal suspended solids, natural organic matter (NOM) and biological contaminants, soluble iron and manganese oxides and hydroxides, hardness and total dissolved solids (TDS), which separates contaminants and produces safe drinking water while eliminating irreversible chemical fouling of the membrane surface, comprising:

• a) Contacting said ground water with air and hydrogen peroxide over a packing contained inside a Packed Column Aerator in order to completely oxidize and precipitate the iron and manganese oxides and hydroxides and produce aerated ground water;
• b) Adding a multi-valent metal coagulant and a cationic flocculant and mixing the chemicals in said aerated ground water to produce a pre-conditioned ground water with a stable floc containing all the colloidal suspended solids, iron and manganese oxides and hydroxides, natural organic matter (NOM) and biological contaminants;
• c) Filtration of said pre-conditioned ground water using a multi-media filter (MMF) bed to separate the flocculated solids and provide pre-filtered water which contains a slight excess of the flocculating catonic flocculant which comprises a polymer and a positive charged associated with said cationic polymer and residual unfiltered particles;
• d) Neutralization and reversal of the excess positive charge in said pre-filtered water to produce a slightly negatively charged pre-filtered water;
• e) Fine Filtration of said slightly negatively charged pre-filtered water using a filter selected from a group consisting of woven fabric depth filters, bag filters, membrane cartridge filters and combinations thereof and having a nominal pore size equal to or less than 5 μm, producing pre-treated water having a Silt Density Index (SDI)<5;
• f) Addition of a scale inhibitor to said pre-treated water in order to prevent scale formation and enable higher permeate recoveries to be obtained;
• g) Addition of acid to said pre-treated water in order to lower the pH, prevent calcium carbonate scale formation and enable higher permeate recoveries to be obtained;
• h) Pressurizing and introducing said pre-treated water into the high pressure side of a membrane system to produce a purified membrane permeate as drinking water on the low pressure side of said membrane system which is free from colloidal and microbial contaminants, and low in iron and hardness, and a membrane concentrate on the high pressure side of said membrane system which contains all residual contaminants and to discharge said membrane concentrate safely to receiving waters or to sanitary sewers;
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• i) Disinfection of said drinking water before distribution.

A further enhanced membrane process for the economical treatment and purification of industrial effluent wastewater containing colloidal, suspended solids, soluble organic compounds, natural organic matter (NOM) and biological contaminants, soluble iron and manganese oxides and hydroxides hardness and total dissolved solids (TDS), which separates contaminants and produces water suitable for recycle or discharge while eliminating irreversible chemical fouling of the membrane surface, comprising:

• a) Adjusting the pH of said wastewater by adding an alkali solution in order to destabilize any iron complexes;
• b) Contacting said wastewater with air and hydrogen peroxide over a packing contained inside a Packed Column Aerator in order to completely oxidize and precipitate the iron and manganese oxides and hydroxides and produce aerated wastewater;
• c) Adding a multi-valent metal coagulant and a cationic flocculant and mixing the chemicals in said aerated wastewater to produce a pre-conditioned wastewater with a stable floc containing all the colloidal suspended solids, iron and manganese oxides and hydroxides and biological contaminants;
• d) Clarification of said floc using a solid disengagement device selected from a group of clarifiers consisting of inclined plate lamella clarifiers, circular clarifiers, gravity settling tanks and combinations thereof to produce a clarifier supernatant containing a much lower concentration of floc;
• e) Filtration of said clarifier supernatant floc using a multi-media filter (MMF) bed to separate entrained flocculated solids and provide pre-filtered water which contains a slight excess of the flocculating cationic flocculant which comprises a polymer and a positive charge associated with said cationic polymer and residual unfiltered particles;
• f) Neutralization and reversal of the excess positive charge in said pre-filtered water to produce a slightly negatively charged pre-filtered water;
• g) Fine Filtration of said slightly negatively charged pre-filtered water using a filter selected from a group consisting of woven fabric depth filters, bag filters, membrane cartridge filters and combinations thereof and having a nominal pore size equal to or less than 5 μm, producing pre-treated water having a Silt Density Index (SDI)<5;
• h) Addition of a scale inhibitor to said pre-treated water in order to prevent scale formation and enable higher permeate recoveries to be obtained;
• i) Addition of acid to said pre-treated water in order to lower the pH, prevent calcium carbonate scale formation and enable higher permeate recoveries to be obtained;
• j) Pressurizing and introducing said pre-treated water into the high pressure side of a membrane system to produce a purified membrane permeate on the low pressure side of said membrane system which is free from colloidal and microbial contaminants, and low in iron, hardness and soluble organic and inorganic compounds and can be recycled, and a membrane concentrate on the high pressure side of said membrane system which contains all residual contaminants which must be treated further and/or sent to safe disposal;
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• k) Disinfection of said membrane permeate before recycle.