Reverse osmosis MPCR
Installation for waste water treatment based on reverse osmosis process performed at vertical modules of disc membranes.
The multistage process RO-MPCR® designed for the direct treatment of highly contaminated wastes has in general the following stages:
1 STAGE: Low pressure (40-60Bar) for the permeate (1 or 2 phase RO).
2 STAGE: High Pressure (80-100 Bar) for the concentrated (MPCR®).
The RO-MPCR® process has in general the following sections:
1. Prefiltration
2. Low pressure stage with RO.
3. High pressure stage with MPCR®.
4. Dosage tank for adjustment of acid pH
5. Dosage tank for adjustment of basic pH
6. Acid cleaner tank
7. Basic cleaner tank
8. Container
Pre – filtration
The water to be treated has been pre-filtered in the treatment plants upstream. However, particles which could damage the system may enter the water during storage in the reservoirs. As a result, the osmosis plant only has one prior safety filter to reduce the solids to sizes between 20 and 50 micron. The replacement of the filters when required does not interfere in the running of the plant as this system does not require the solids to be completely eliminated. The filtering is carried out to improve the plant’s performance and to reduce the dirt on the membranes, thus extending the useful operating life of the membranes. The raw water pre-filtration process uses cartridge or bag filters. Each case is analysed to determine which system is most appropriate. The pressure required for circulation is provided from an internal pressure pump. The refining filters provide optimum protection for the membranes. They should be changed when the pressure reaches 2 bar – 2.5 bar. If a filter needs changing, this is shown on the control panel. As a general rule, and also as a system to prepare the waste in order to optimise
filtration, the pH value in the raw water must be adjusted to prevent uncontrolled precipitation.
Low pressure stage with RO
The membranes used for reverse osmosis have a dense barrier layer in the polymer matrix where most separation occurs. In most cases the membrane is designed to allow only water to pass through this dense layer while preventing the passage of solutes (such as salt ions). This process requires that a low pressure be exerted on the high concentration side of the membrane, usually 2–17 bar for fresh and brackish water, and 40–70 bar for seawater, which has around 24 bar (350 psi) natural osmotic pressure that must be overcome. MP Environment has designed the operation of this stage avoiding the disadvantages of this technology, so that the normal working pressure of the RO is very low and concentrated generated very high, so we avoid the unwanted formation of scale and greater efficiency in yields.
High pressure stage with MPCR®
After the RO, water is pumped to the distribution line at high pressure using the high pressure pump. At the end of the distribution line (concentrate) there is a motorised valve which controls the pressure. The high pressure pumps push the water through the MPCR® membrane module. The raw water flow is flexible and can be adjusted to requirements. Where raw water storage reservoirs are available, the input flow of the raw water can be designed according to average treatment values.
If necessary, the plant may operate discontinuously. It is even possible to disconnect the plant for prolonged periods without problem. The plant operates automatically so that if, in normal operating conditions, the plant does not reach the nominal permeate production at the operating pressure, the supply raw water flow is adjusted (reduced) until the minimum acceptable level of permeate is obtained. When the minimum permeate volume has been obtained, the cleaning cycle for the sector concerned starts automatically while the rest of the plant continues operating normally. The MPCR® vertical membrane modules is connected on a frame. The unit can be mounted under cover in which case it is assembled directly inside a standard container. It is also possible to move the stage, at a later moment, from the container to under cover without any changes.
The pressure stage has the following components:
• Control box
• Low voltage distribution
• Frequency transformer
• Measurement equipment
• High pressure pump
• Modular block of in-line pumps
• Permeate tank with filler pump
• Cleaning tank with pump
• Pneumatic control valves
• Pipes: Low pressure material: PVC; High pressure material: stainless steel
1.4466/1.4539
• Compressed air supply
• Acid cleaner dispenser system
• Alkaline cleaner dispenser system
The plants are built to suit the customer’s requirement in modular form. The individual sections are mounted on a stainless steel frame (1.4301) guaranteeing a longer life for the equipment. The units are designed so that they can be installed indoors or inside a container (standard ISO size). No technical changes are required for the installation in the container.
The standard modular format permits the assembly of the units at our factory, ready for operation, including empty and loaded tests. This system permits the rapid installation and immediate start-up of the plant at the site as required.
Cleaning system:
A cross-flow membrane filtration system must be easy to clean. Even with the MPCR® modules, it is not always possible to avoid the build-up of elements on the membrane surface. The build-up of inorganic elements produced in different forms, such as crystallisation, is called scaling and the build-up of organic materials is referred to as fouling.
With an appropriate technical design and the use of top quality components, it is possible to clean the surface of the membranes and permit the subsequent removal of the waste. The fundamental advantage of the MPCR® modules lies in the open channel system. The raw water passes through flat channels with a minimum height of 500 μm. Any build-up is detached using cleaning agents and subsequently removed from the module. The units have an internal cleaning circuit which can be operated manually or automatically. The modules can be cleaned using three different modes, according to the type of scaling/fouling. The necessary cleaning agents are automatically dispensed from the dosage tanks designed to reduce consumption. The plant includes an automatic dispensing system for alkaline cleaner, acid cleaner and anti-scaling solution.