The ever increasing demand for ultra-pure water in various industrial sectors such as pharmaceuticals, electronics, petrochemicals and power generation, combined with the decrease of available water, have forced manufacturers of water treatments plants like Bono Artes (Cannon Group) to implement the best solutions available to obtain high yields in terms of quality and quantity.
An efficient and environmentally-sustainable exploitation of the energy resources requires the implementation of systems with the highest standard of efficiency and lowest consumptions and waste.
Traditional reverse osmosis systems have limited recovery capacity (the percentage of water suitable for use in the total of water treated) due to fouling and scaling of the membranes arising from the characteristics of the feed-water. In many cases though, the scarcity of water and high concentration of pollutants imply that conventional membranes systems may not be suitable. For example, the maximum amount of silica that can be removed with traditional reverse osmosis systems does not exceed 90%; and where silica concentration is greater than 80-100 ppm, the fouling due to its precipitation, notwithstanding the addition of chemicals, allows less than 50% recovery of ultra pure water.
Power generation plants require boiler feed-water with the lowest concentration of silica. Although it has no direct corrosive effect, silica tends to form residual deposits that are difficult to remove from the walls of boilers and turbines, reducing heat transfer coefficiency and increasing the risk of structural failures.
Bono Artes has successfully addressed these problems by implementing a “specialist” reverse osmosis system capable of removing great quantities of silica with a high ratio of recovery.
For this project Artes Bono has signed a collaboration agreement with Debasish Mukhopadhyay who has patented a special reverse osmosis system called HEROTM (High Efficiency Reverse Osmosis); this system, which works with high pH and high-speed primary and secondary flows, can significantly increase the performance of Reverse Osmosis Water Treatment Plants.
The plant was designed to treat the feed-water in the 800 MW Combined Cycle Power Plant built by Ansaldo Energia in Sparanise in the province of Caserta, South of Italy.
The feed-water in this plant comes from wells, which in these areas are characterized by very high silica content (above 80 ppm), while the permissible limit in treated water imposed by the supplier of the turbine is below 10 ppb, so this project required a high efficiency of silica removal exceeding 99.99%. In addition, the customer had imposed the minimum use of water requiring a recovery ratio exceeding 80%.
Bono Artes has successfully achieved this goal by installing a dual passage Reverse Osmosis system followed by a Membrane Contactor (MC) and an Electro-deionization (EDI) unit.
The recovery and reuse of water is a fundamental challenge to cover the shortage of supply and arrive at zero liquid discharge (ZLD) systems. The realization of the Sparanise plant, commissioned in early 2008, has further strengthened Artes’ already consolidated experience in this sector.
Key benefits of HEROTM technology are:
- Ability to operate the reverse osmosis with a higher ratio of recovery
- Production of ultra pure water, thanks to increased efficiency due to high Ph
- The high pH inhibits bacterial growth and the creation of biological film
- Reduced precipitation of inorganic salts through the destabilization of colloids and an increased solubility of silica
- Reduced footprint compared to conventional plants
- Reduced operating costs
- Negligible cleaning operations, since the high pH keeps the membranes clean