Thursday, July 28, 2011

Industrial Water Reuse

By Colin Frayne, Association of Water Technologies and Aquassurance Inc.
May 1, 2011

Colin Frayne's books on water treatment can be found here

Reduce, reuse, recycle are not just buzzwords: They are tools of an effective water management and treatment program that can help processors improve their bottom line.

The rapid growth of world population — doubling every 20 years and currently heading for 7 billion people — means significantly increased global water use and resultant decrease in availability on a per capita basis. Couple this with the fact that Brazil, Russia, India and China (collectively known as the BRIC countries), and countries in Southeast Asia such as Malaysia, Indonesia, Thailand and Vietnam have both very young populations — all wanting the trappings of Western life — and are rapidly building up their own water-demanding industries and infrastructures. It is becoming clearer day by day that there soon will not be adequate readily available fresh water for all of us on this planet!

As a response to the unsustainable climate and resources position within which we find ourselves, in recent years, various national and international “green” organizations have sprung up. These organizations, focused on promoting conservation and sustainability, have developed best practices such as “green” water management programs for water-based heat-transfer systems. Also, the U.S. Department of Energy provides free Internet-based software for industrial water and energy assessments, optimization and savings.

How Much is too Much?

By Colin Frayne, for Association of Water Technologies and Aquassaurance inc.
May 1, 2011

Increasing cycles of concentration can allow processors to reuse waters and minimize water use. The typical practical contaminant maximums in recirculating cooling water are shown.
  • Alkalinity: total alkalinity (M alkalinity). A practical limit is often 500 mg/L as CaCO3, although up to 800 mg/L CaCO3might be achievable, depending upon water chemistry.
  • Ammonia (NH3).Up to 20 to 40 mg/L can be tolerated if the copper content is low, water temperatures are not too high, good microbiological control is maintained, and waterside surfaces are kept clean.
  • Chemical Oxygen Demand (COD). Say, less than 100 mg/L
  • Calcium. A practical limit for total hardness is often 600 mg/L as CaCO3, although with top quality inhibitors and tight control, up to 1200 mg/L as CaCO3 might be achievable.
  • Chlorides. The lower the better, as chloride is a depassivating ion and reduces the corrosion resistance of many constructional metals. Perhaps 500-600 mg/L chloride in carbon steel systems, but only 200 mg/L maximum in systems containing 304 stainless steel. Also, the system metal surfaces must be kept scrupulously clean!
  • Iron. Iron salts (and to a lesser extent manganese salts) are often to be found in recovered waters and can be ignored unless the level rises to perhaps 0.3 mg/L or more.
  • Oil, Solvents and Hydrocarbons. Even small traces of oil can reduce chemical inhibitor performance and impede heat transfer and therefore must be eliminated.
  • pH. Typically, from pH 7.0 to 90.0
  • Phosphate. Phosphate in recovered waters can often be used as the basis of a chemical inhibitor program. Say 2-3 mg/L total PO4.
  • Silica. The limit of solubility in recirculating cooling water is typically around 150 to 175 mg/L and should not be exceeded.
  • Sulfate. Sulfates are causative agents (along with oxygen, hydrogen, etc.) of various types of concentration cell corrosion, Usually, say, 1800 mg/L is the maximum limit but this varies with several factors. Up to 2,300 mg/L has been tolerated in suitably conditioned systems.
  • Suspended solids (SS). Maximum tolerated levels of SS in recirculating water is perhaps 50 to 60 mg/L.

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Expert Colin Frayne on Influent Water Systems

Is Water the New Energy? Expert Colin Frayne on Influent Water Systems

by Amanda Moreno, Editor-In-Chief

These days, a glass of water is valuable commodity, and not just because we’re sweltering in the midst of those hot summer months. As the population increases, so does our global industrial water usage, which is why Knovel’s next seminar Designing & Managing Influent Water Systems- Keys to Minimizing Risk & Maximizing Flexibility, is such a dynamic topic.

The webinar panel features industry expert Colin Frayne, an accomplished industrial chemist, corrosion engineer and environmental scientist, whose published works include Boiler Water Treatment – Principles and Practice, Volumes I-II and Cooling Water Treatment – Principles and Practice. I recently spoke with Colin to delve into his expertise on responsible water reuse practices.