Clean Water Membrane Systems

Overall Summary

Primary Application

• Dairies desiring significant reduction in liquid manure storage volume and added flexibility in land application options.
• Dairies under unique constraints related to storage capacity, lagoon construction/cost, and/or manure hauling to distant fields.
• The technology is available at any scale.
• Both raw and digested manure can be treated but significant pre-treatment of those manures is required.
• Technology is applicable to all climate conditions.

Economic/Return on Investment Considerations           

• Capital costs are a concern with installed costs on the high end.
• Operating costs are high, with systems incurring high electrical and chemical costs.
• Significant offset of manure management costs. From 40-70% of pre-treated liquid volume can be converted to ‘clean water’ not requiring storage and application.
• Although markets are not mature, and several factors impact its viability, the concentrate resulting from the removal of water, can be sold for value.

Industry Uptake

• As of 2018, the number of U.S. installations is around one dozen, mostly at dairies of a smaller size.
• An analysis of locations shows the adoption of the technology to dairies with unique costs related to liquid storage/application.

Technology Maturity

• The state of the technology in the U.S. is emerging. Presently, significant concerns exist relating to operational uptime, reliability, and true operational costs.
• Multiple vendors and configurations exist, with systems using varying types, forms and sequences of membranes.

Primary Benefits

• Storage volume reduction, 40-70% of incoming liquid resulting in ‘clean water’ suitable for either discharge, use as process water or animal drinking water—pending meeting local and federal regulations.
• Nutrients partitioned into a concentrated liquid product.
• Produces a concentrate containing virtually all of the incoming nutrients/salts.
• Negligible impact on odor is seen with this technology.
• Produced concentrate can have bacteria/virus partitioned into smaller volumes, although the pathogens are not destroyed.
• GHG mitigation is negligible as the initial organics remain in the concentrated form.

Secondary Benefits

• Offsets to existing manure management, specifically lagoon storage maintenance/construction and liquid transportation.
• ‘Clean water’ produced by system can potentially be used as process water, animal drinking water, and new water rights upon discharge to streams—all of which can produce limited offsets and/or revenues, with proper permitting.
• Produced concentrate could be certified organic, producing a value-added liquid fertilizer concentrate for the organic market.

How it works

• Pre-treated manure, with suspended solids removed, are passed through a sequence of membranes using high-pressure pumps. As the liquid enters the membranes, certain nutrients/salts/pathogens are rejected by the size of the membrane while water and other species pass through.
• The rejected material becomes the liquid concentrate while the pass-through becomes the ‘clean water’
• The end products of the process are the liquid concentrate containing the bulk of influent nutrients/salts and a ‘clean water’ with potential for discharge, use as process water, and/or animal drinking water, pending permitting.

Pretreatment and/or Post-treatment Required

• Effective pretreatment is essential. For protection of the membranes, manure must be removed of nearly all suspended solids.
• The liquid concentrate will require storage/application while the ‘clean water’ will need to meet permitting requirements for desired end-use. In the case of discharge to U.S. waterways, a particularly intensive permitting process, the post-treatment might require additional treatments such as ion exchange, activated carbon, oxygenation, outflow processing, etc.

Limitations

• Key limitations of the technology center on both the high cost and on-going concerns with reliability.
• No renewable energy is produced in this system and considerable electrical energy is required.
• No thermal renewable energy is produced in the system.

Other Considerations

• Successful projects require a correct matching of technology with specific volume reduction and corresponding reduction in transportation costs.
• Correct choice of system and operations/maintenance are required to overcome historic reliability and performance concerns.
• Creative use can decrease costs, such as operating the system only during the winter months of required storage or only treating a fraction of manure.
• Pretreatment with chemical coagulants or flocculants could impact organic certification.  Review of products used should be conducted to determine potential effects on certification. 

Skilled operations/maintenance, either internal with training or external with professional services, are required for sustained and reliable operation