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10 Questions to Consider about Industrial Water Reuse

As economic drivers and environmental stewards, industrial facilities and complexes are vital components to a community. Water reuse for industrial processes has numerous sustainability features that can benefit the surrounding region, but reuse is not a viable option for every situation. Because each facility presents site- and process-specific factors, water reuse consideration requires thorough data collection and careful analysis of the many options available. Here are 10 questions to consider before implementing water reuse.

  1. What water quality is needed for reuse? Potential water reuse options include land application or disposal, landscape irrigation, cooling, cleaning/sanitation, boiler makeup, process and production water. Each requires increased water quality and cost in the order they are stated.

  2. What are the water flows? Start with a water survey that considers daily and seasonal variations, assesses current and future water use (both quality and quantity), and determines potential sources of recoverable water.

  3. What are the future water demands and sources available? Conduct a water-needs study to predict future demands, potential onsite conservation and alternative sources that can be used to ensure sustainable operation.

  4. Can wastewater segregation be achieved? If restroom wastewater cannot be separated due to combined wastewater systems, there may be limitations on water reuse or sludge disposal options. Additional disinfection, extensive permitting and related perception concerns must be considered.

  5. Is flow equalization needed? Depending on flow rate variation (not just daily volume), batch dumps, seasonal variations and sanitation processes, equalization may be warranted prior to treatment component sizing. Properly designed equalization tanks can minimize downstream treatment component size and costs.

  6. What is in the wastewater? Sampling and analytical testing is needed during various production process conditions to determine treatment system loadings and the presence of non-traditional analytical parameters such as salts, hardness, pH, silica, cations and anions. Process streams can vary considerably in biochemical oxygen demand, fats/oil/grease, total suspended solids and temperature, and soluble versus particulate matter may affect the required treatment process. (Note that not all constituents are bad, such as nutrients that may be beneficial if the reclaimed water will be used for landscape irrigation.)

  7. How much space is available? Generally, biological treatment is needed for removal of soluble organics in industrial treatment plants. This may be in the form of large lagoons and activated sludge may require large concrete tanks instead of lagoons. For both, consider available space.

  8. What sludge disposal options are available? Consider water reuse in comparison to alternative options, including full or partial disposal of residual solids. It is not uncommon to underestimate the volume of sludge produced, and the solids management in a treatment plant can easily affect the treatment efficiency and reuse water quality.

  9. Where will reject water be disposed? In reuse scenarios that use reverse osmosis and other membrane-based processes, the concentrate stream must be carefully managed and disposed. If this stream cannot be discharged to the publicly operated treatment works, then onsite evaporation or further concentration of the reject may be required, thereby significantly increasing costs and space required.

  10. What are the potential costs and savings? There is a direct correlation between the level of water quality required and implementation expense. Reuse scenarios should consider a life-cycle cost analysis, where capital, operation and maintenance costs rise somewhat exponentially along with an increase in required operational competence. Savings also need to be considered on a life-cycle base and can include reduced purchase cost of water, wastewater treatment fees to a sewer publicly owned treatment works, cost of compliance monitoring (if zero liquid discharge can be achieved), and treatment for current water supply.

Treatment technologies are available to achieve any desired level of water quality and the level of treatment required depends on the reuse application. For most industrial uses of reclaimed water, conventional processes involving secondary treatment, filtration and disinfection steps are sufficient to achieve necessary water quality. In applications where human contact increases, advanced treatment may be required. Whatever the application, the sustainability benefits of water reuse include reduced demand on water supply, wastewater disposal and impact on the local community.

You can learn more about industrial water reuse in the U.S. Environmental Protection Agency 2012 Guidelines for Water Reuse (see page 106).

Al Goodman, PE, of CDM Smith is a recognized international expert on water and wastewater. For more than 40 years, he has provided wastewater plant troubleshooting, technical and process load evaluations, compliance negotiations, strategy planning for budgeting, operator and process efficiency evaluations, and operator training for industrial and municipal clients. 

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