Wastewater treatment systems

Today membrane technologies are widely used for different industrial waste water treatment. High level of purification allows achieve all the requirements for open water surfaces and ground waters protection. This system is specially efficient when isused in combination with micro and ultra filtration stages.

3D model of membrane treatment unit

Main peculiarity of membrane bioreactor (MBR) from conventional air tank treatment system is presence of membrane module which is used for detachment of sludge and is perfect alternative for sludge sedimentation in secondary sedimentation tanks. Membrane module consists of 10-20 membrane cartridges. Each cartridge has from 5 to 10 membrane fiber bunches. Empty fiber membrane is string with outer diameter about 2 mm and up to 2 m length. The string surface is an ultra filtration membrane with pore dimension 0,03 – 0,1 micro meter. Each bunch consists of 100-1000 membrane fibers and equipped with pipe for filtrate discharge. The pore dimension is physical barrier sludge microorganisms penetration as their dimension is more then 0,5 micro meter. Thanks to that it is possible to detach activated sludge from water and decrease concentration of suspended solids in treated water to the value of 1 mg/l and even less. Filtration is performed with the help of vacuum that is made on internal membrane fiber surface by self-priming filtration pump. At that mixture of waste water and activated sludge is filtrated by membrane surface from outer to inner surface. Purified water is directed by flow pipe to disinfection unit and activated sludge is constantly kept in suspended state by aeration system of membrane module.

Technology peculiarities

1. Refusal from gravity sludge detachment system allows make activated sludge concentration in bio reactor 10-20 g/l (conventional air tank value up to 3 g/l).

2. Hi concentration of activated sludge makes possible bioreactor operation in low loading mode that makes reserve for oxidation ability, increases biocoenosis stability. In comparison to gravity method changes in biocoenosis of activated sludge can be traced. Sludge age in MBR makes 25-30 days and sometimes increases 60-70 days. At that main part of activated sludge is represented by low growing micro flora, which is most efficient for decomposition of hardly oxidation organic substances in waste water. Low growing micro flora predomination allows considerable reduction of activated sludge increase and as a result decreases capacity of sludge dewatering equipment.

Membrane module in operation

3. Allows following results for waste water treatment efficiency:

• BOD: more then 98%;
• COD: 85-95%;
• Suspended solids: less then 1 mg/l;
• Ammonia nitrogen: morethen 98%;
• Heavy metals removal: 25-80%;
• Bacteria removal: more then 99,999%;
• Viruses removal: more then 99,9%.

4. Activated sludge flakes dimensions 5-10 times less then in other aeration systems. Such activated sludge dispersity leads to wider contact area of microorganisms and waste water. As a result the inert substances, heavy metals, micro waste adsorption efficiency increases.

5. Due to small dimension of membrane pore that is smaller then bacteria and virus cell, partial disinfection in MBR is performed. Bacteria removal efficiency 99,999%, viruses removal efficiency 99,9%. Waste water treated in MBR can be reused for non potable purposes.

6. High sludge concentration can decrease retention time of waste water in treatment facility. As a result the area for treatment plant 2-4 times less then conventional systems require.

7. As an option MBR can be produced in container that will considerably decrease capital costs.

Characteristics

Characteristics	1 modification	2 modification	3 modification	4 modification
Efficiency, tons/day	300	600	1000	1500
Electricity consumption, kWh	26	51	86	129
Flocculating agent , kg/day	6	12	20	30