Solids Separation and Concentration of Shipboard Wastewaters and Residuals by a High Shear Rotary Membrane System
WP-1671
Objective
Navy ships generate a variety of wastes: bilge water, blackwater, graywater, shipboard “industrial” wastes, and solid residuals from existing treatment systems. Many of the Navy’s current waste treatment systems would benefit from the efficient removal of solids (e.g., oily waste ceramic membranes are susceptible to face plugging and mechanical failure). However, available solids removal technologies have not been particularly effective, necessitating the development of improved solids removal technologies. A High Shear Rotary Membrane System (HSR-MS) has shown superior abilities to separate and concentrate Navy and non-Navy wastewater solids (e.g., oily wastes, underwater hull cleaning sludge, non-skid deck cleaning wastewater, tank car latex waste, and metal hydroxide suspensions). However, HSR-MS has been confined to land-based applications where space is not a critical design consideration. This project seeks to overcome current HSR-MS limitations for shipboard placement.
The overall objective of this project is to develop a robust shipboard system capable of managing multiple Navy solids-bearing wastes. Specific objectives are to (1) increase HSR-MS permeate flux and decrease system size by employing backpulsing and continuous physical membrane cleaning; (2) increase “active” membrane packing density (active membrane area/system footprint and volume) by using larger diameter and/or overlapping disks; and (3) conceptually design, fabricate, and test a laboratory-scale HSR-MS incorporating a combination of backpulsing, continuous physical cleaning, larger disks, and disk overlap. Meeting the objectives will provide an improved HSR-MS with increased throughput and smaller footprint or space requirements.
Technical Approach
HSR-MS is a barrier technology using ultrafiltration or microfiltration membranes to separate practically all solids (e.g., particles, oils, fibers, and colloidal particles) from liquid waste streams. During membrane separation, solids that accumulate at the membrane surface decrease throughput and are the major factor limiting membrane use. Conventional cross-flow systems pump the waste at high flow rates and cross-flow velocities parallel to the membrane surface creating a scouring or cleaning action. However, at high feed concentrations and viscosities, pumping becomes difficult, and the high velocities needed to scour the surface are not possible. In contrast, HSR-MS consists of stacked rotating membrane disks that produce greater turbulence and shear at the membrane surface. By rotating the membrane, scouring energy is applied exactly where it is needed (i.e., membrane surface). Decoupling the feed delivery and the pressurization from turbulence and shear promotion allows the HSR-MS to produce highly concentrated wastes, operate at lower pressures, reduce fouling layer compaction and pore plugging, increase membrane life, and decrease cleaning frequency and residuals production.
Benefits
Shipboard applications to be improved by HSR-MS include (1) more efficient solids removal prior to existing shipboard treatment processes; (2) direct replacement of problematic treatment systems with the more robust, higher efficiency system; and (3) concentration of sludge, waste oil, and process residuals. The ultimate benefit to the Department of Defense is a robust “barrier” technology that is easy to operate, not labor intensive, capable of being cleaned in place, able to withstand harsh environments, and potentially mobile. (Anticipated Project Completion - 2012)
Points of Contact
Principal Investigator
Tracy Carole
Naval Sea Systems Command (NAVSEA)
Phone: 301-227-4893
Document Types
- Fact Sheet - Brief project summary with links to related documents and points of contact.
- Final Report - Comprehensive report for every completed SERDP and ESTCP project that contains all technical results.
- Cost & Performance Report - Overview of ESTCP demonstration activities, results, and conclusions, standardized to facilitate implementation decisions.
- Technical Report - Additional interim reports, laboratory reports, demonstration reports, and technology survey reports.
- Guidance - Instructional information on technical topics such as protocols and user’s guides.
- Workshop Report - Summary of workshop discussion and findings.
- Multimedia - On demand videos, animations, and webcasts highlighting featured initiatives or technologies.
- Model/Software - Computer programs and applications available for download.
- Database - Digitally organized collection of data available to search and access.