Ultrafiltration Membranes

Jan. 1, 2006
UF systems meet growing demand for pure water at pharmaceutical plant in Puerto Rico

About the author: David Lazar, Lazar Creative Group. For additional information, contact Jorg Menningmann, general manager of ITT Aquious –Water Equipment Technologies at 561.684.6300, or by e-mail at [email protected].

With an aging and often overwhelmed water supply infrastructure, evermore stringent government regulations and growing industrial requirements for pure water, municipalities and companies are increasingly turning to ultrafiltration (UF) membrane systems for water and wastewater treatment.

In communities with fast-growing populations and a commensurate increased demand for drinking water, UF membranes provide an economical, effective treatment solution for delivering increased system capacity while protecting consumers from viruses, bacteria and other harmful pathogens, and ensuring regulatory compliance.

Water reuse is now mandatory for many municipalities. UF systems are increasingly being employed by water utilities in wastewater treatment systems because they allow a significant amount of wastewater to be reused.

In industrial applications, the treatment of raw groundwater and surface water using UF can be highly beneficial, and in some cases, essential. UF treatment often results in better operating reliability and a longer operating lifetime for the downstream plant and equipment.

Packaged UF Systems

The range of packaged UF membrane systems from ITT Aquious offers users reliability and robustness across a wide array of municipal, commercial and industrial applications. The membranes used in the Aquious UF systems have been approved for drinking water applications by the majority of the world’s regulatory agencies, meeting both North American and European standards.

Pressurized hollow fiber (HF) membranes form the core of the UF process, providing a physical barrier to contaminants. Product water quality surpasses that of conventional coagulation, clarification and filtration processes with the benefit of simple operation and low life-cycle costs.

Aquious provides UF systems as standard skid-mounted packages to minimize costs—combining all necessary pumps, instruments, valves and other standard equipment—and offer complete treatment solutions. A wide variety of options are available to tailor the standard designs to meet specific customer needs. Aquious also offers customized systems supported by comprehensive, in-house design and engineering capabilities.

UF in Plant Pretreatment

In a recent installation, Aquious provided a UF system for the pretreatment of process water in a pharmaceutical manufacturing plant in Puerto Rico. Aquious was asked to deliver a solution to replace an existing RO system that was experiencing significant fouling issues, making the system difficult and unreliable to operate. These problems were burdening the customer with substantial operating and maintenance costs from membrane replacement and chemicals to prevent fouling. After analyzing the entire water treatment system, the engineers proposed a UF pretreatment system followed by a dual-stage RO system.

Installing the UF system for water pretreatment served to reduce turbidity and SDI, protecting the RO membranes. The UF system acts as a barrier to filter suspended and colloidal matter, and thus provides high quality water so the RO membrane system can operate efficiently. The UF system contains HF membranes that go through a series of backflush cycles during the day (up to 200 cycles per day) to remove the impurities that have been deposited on the UF membranes. The addition of the pretreatment UF system has greatly reduced RO system fouling. The combined UF/RO system installed by Aquious has been operating since 2002, and the RO membranes have not been changed once.

Meeting Demands

A wide range of feedwater streams may be used for the Aquious UF systems including surface water, groundwater, wastewater and treated drinking water. This makes the systems suitable for a wide range of applications, including:

  • Providing potable water for municipal and private drinking water supplies;
  • Providing industrial process water and irrigation water for agriculture;
  • Recovering filter backwash water;
  • Pretreating water prior to subsequent enhanced purification processes;
  • Treating industrial effluent and domestic sewage; and
  • Reusing wastewater.

The Aquious UF systems consistently provide high quality water. Pathogen and colloid/particle removal rates are up to 6 log for bacteria and 4 log for viruses. In the water output, suspended solids are less than1.0 mg/L and turbidity is less than 0.1NTU (based on feedwater with suspended solids less than 200 mg/L).

With day-to-day system operation a significant concern, the Aquious UF package systems have been designed with automation and low power consumption, providing users with a low life-cycle cost solution. The systems can be operated in dead-end or recirculation modes, allowing recovery rates to be maximized, thus saving precious raw water resources. Filtration efficiency is maintained at optimum performance using automated membrane cleaning—regular backwashing using permeate water and periodic chemically enhanced backwashing. The systems have also been designed to require the minimum footprint and headroom.

With a minimum inlet pressure of 20 psi/1.5 Bar (less with a feed pump) and a maximum inlet pressure of 72.5 psi/5 Bar, the systems do not require both feed and relift pumps where adequate water pressure is available. Fully assembled and tested prior to delivery, the proven operation of these systems is backed by system and membrane performance warranties.

The Aquious UF packaged systems employ polyethersulfone membranes to provide the significant advantages of high chlorine and wide pH tolerance, as well as a high permeability (flux) and low fouling characteristics. The membranes operate on the inside-to-out principle and provide a 200kDa molecular weight cut-off, thus retaining a wide variety of potential contaminants. The membranes are housed in pressure vessels (known as modules), which are quick and easy to replace. Their low cost helps to ensure that the overall life-cycle costs of the systems are highly competitive.

About the Author

David Lazar