Membrane pilot testing, from sample to plant

Bench tests screen membranes on a small sample. The US Environmental Protection Agency (EPA) notes, for example, that reverse osmosis and nanofiltration membranes can be screened for some parameters with flat-sheet or single-element tests. A pilot goes further: it runs on the real feed at the site, and the pilot process should be representative of the full-scale system, including any pretreatment the plant will have. Its data size the plant and narrow the uncertainty about footprint and utilities, they help catch conditions that would otherwise go undetected, and the run familiarizes operators with the equipment.

The EPA figures on this page come from its guidance on membrane filtration for drinking water (microfiltration, ultrafiltration, nanofiltration and reverse osmosis), which it offers as general guidance on widely recognized industry practice. AQUA-SEP® uses vacuum membrane distillation, and AZEO-SEP and VOC-SEP use pervaporation, processes that guidance does not cover, so it frames the method, not the numbers for these systems.

1. Feasibility study. Petro Sep's brochures list technical assistance, consulting and feasibility studies on complex fluid separation problems among its services. Its AQUA-SEP deck describes turnkey work that runs from research and feasibility through conceptual design, FEED and detailed engineering to fabrication, construction, and project and operations management.
2. Bench-scale tests on a sample. For AZEO-SEP and VOC-SEP, the brochures put bench-scale testing at Petro Sep's Canadian labs and R&D center first among the ways it helps a customer choose the best system. The lab is in Mississauga (Greater Toronto Area); its services are on the lab testing and analytics page.
3. A pilot unit on the real feed. For AZEO-SEP and VOC-SEP, the same brochures list sales and rentals of bench-scale or pilot plant testing units. In the EPA's guidance, the pilot should match the planned plant, pretreatment included, and the test site supplies the unit's utilities (see "Can you rent or buy a pilot unit?" below). Petro Sep's records include the factory acceptance test (FAT) of a pilot unit in the USA in 2015.
4. The pilot report. In the EPA's guidance, the report should hold enough detail to set the full-scale plant's design parameters, to the extent the testing intended. A pilot's result is not necessarily the "optimum" design but a set of operating conditions that is feasible and economic over the expected range of operating and feed conditions.
5. Engineering, fabrication and installation. The brochures' third way is customized engineering and design for the application. Petro Sep's Company Profile lists its services as research and development, engineering and design, fabrication and installation, operations management, and collaborations and partnerships. Scale-up is covered on process modeling and scale-up.

The EPA adds that only one process variable should be changed at a time. A pilot is also measured against its own goal: in Petro Sep's Lean Water pilot, organic levels low enough for sewer discharge instead of incineration.

For drinking-water filtration, the EPA calls piloting through at least three cleaning cycles recommended practice. For hollow-fiber microfiltration and ultrafiltration, which typically target at least 30 days between cleanings, that means 90 days where possible, and for a more thorough study it usually recommends about 4 to 7 months (3,000 to 5,000 hours) of cumulative operation. It puts nanofiltration and reverse osmosis pilots at about 2 to 7 months (1,500 to 5,000 hours) of cumulative operation, longer for water of variable quality, and says a longer pilot may suit newer, less proven systems. These are general filtration figures, not Petro Sep's; ask for a schedule for your feed.

AZEO-SEP units are custom designed, bench-scale or skid-mounted, and supplied on a turnkey basis, either stand-alone or as part of a hybrid separation process. VOC-SEP units are skid-mounted and compact, for ease of transport and installation. Pilot plant fabrication is covered on the pilot and demonstration plants page.

Whoever supplies the unit, the test site has to host it. The EPA's list: utilities such as water, electricity and air; plumbing for the feed, filtrate and concentrate; disposal of cleaning residuals; an estimate of the labor to operate the unit; and enough space. Ask Petro Sep for unit availability and terms.