Technology Strengths, Weaknesses and Critical Indicators
Ultra-Filtration (UF) Membrane Based Nutrient Removal technologies can be used to reduce both suspended and dissolved solids depending on location specific requirements:
- Produces low nutrient irrigation water and marketable products when paired with other technologies
- Always produce a stream leaving membrane and stream rejected by membrane
- Membranes of various size: Micro-filtration, Ultra-Filtration and Nano-Filtration each allowing various sized particles through the membrane
- Depending on the membrane, effective pre-treatment to remove coarse, fibrous solids as well as fine suspended solids are important to system viability and reliability
- Membrane failure and high pressure/energy costs can be a concern
- Proven technology for nitrogen recovery, phosphorous recovery, and pathogen reduction.
- The primary application is as a system to further partition solids after primary solids/liquid separation, but in this case into a concentrated slurry and a ‘tea water’.
- The system is designed for treatment of scrape/flush slurry manures, with sand-laden manure slurry a concern due to wear/tear on the membrane.
- No climate condition limitations exist with this technology.
- The produced ‘tea water’ and concentrated nutrients can potentially be certified organic because there is no addition of chemicals, beyond those required for periodic membrane cleaning
Economic/Return on Investment Considerations
- Comparative to other advanced solids separation systems for production of ‘tea water’, the system has high capital costs.
- Operating costs are in the medium range, with little to no chemical costs, but with increased electrical costs.
- Cost reduction opportunities reside in the manure management offsets that result from the use of the technology as well as potential organic certification for value-added products deriving from additional downstream processing.
- Notably, in contrast to other advanced solids separation systems, the by-product after solids separation is not a stackable solid but a slurry requiring liquid storage.
- At present UF membranes are used across the world and U.S. in many wastewater and food processing industries however adoption is limited on dairies, especially in U.S. due to concerns with cost and operations.
- Presently, a dozen or so installations in the U.S. utilize UF membranes as a part of their larger clean water membrane approach, although demonstrations exist for their sole-use in production of ‘tea water’.
- The state of this technology is emerging, particularly in its sole-use for ‘tea water’ and development of its markets.
- There are several vendors supplying different configurations and designs.
- Partitioning of the bulk of organic nitrogen and total phosphorous within the slurry concentrate, yielding a ‘tea water’ with manure/nutrient management offsets.
- Little benefit is realized in odor management as the bulk of organic material still exists.
- No volume reduction is realized.
- UF membranes will block bacteria/virus from entering the ‘tea water’, thus potentially producing a liquid fertilizer capable of meeting food safety modernization act (FSMA) regulations.
- As there is no loss of organic material, little to no greenhouse gas mitigation is realized.
- The UF membrane has historically been used as a first sequence membrane in further membrane treatment to produce clean water, so can play a role as a stand-alone solids/liquid separation process, or as a part of a system for ‘clean water’.
- The key secondary benefit is the offset to baseline manure management costs.
How it works
- The system works by introducing a low-solids slurry/liquid into the membrane using high-pressure pumps, allowing the membrane pores to preferentially pass through nutrients like ammonia and salts along with water, while blocking large solids containing most of the phosphorous, organic-N and bacteria/virus.
- Two co-products are produced, the concentrated slurry and the ‘tea water’.
Pretreatment and/or Post-treatment Required
- Primary separation of the slurry is required as a pretreatment prior to use.
- Liquid/slurry storage is required for both produced co-products.
- Concerns on cost and reliability/performance.
- Separation does not produce a stackable pile of solids but a concentrated slurry still in need of storage/application.
- The system does not produce renewable power, fuel and heat and requires electricity for its operation.
- Key to success of this technology is the value-added use of the ‘tea water’.
- Professional training, either in-house or through professional services aids in greater performance and up-time.
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