Page 21 - Membranes for Industrial Wastewater Recovery and Re-Use
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2  Membranes for lndustrial Wastewater Recovery and Re-use

          1.1 Water  reuse motivations and barriers

          The motivations for recycling of  wastewater are manifold. Most often stated are
          those  pertaining  to  increasing  pressures  on  water  resources.  Reuse  of
          wastewater  conserves  the  supply  of  freshwater,  and  this  presents  clear
          advantages  with  respect  to  environmental  protection.  More  pragmatically,
          wastewater  reuse  may  result  directly  from  legislation,  which  can  constrain
          the discharge  of polluted  water by  making  this option  onerous or  else forbid
          such discharges altogether, or it may simply be favoured economically regardless
          of regulatory stipulations.
            It is also the case that reuse itself is an emotive issue, and perhaps particularly
          so in the case of water. For domestic water recycling, that is recycling of water for
          non-contact domestic use such as toilet flushing or irrigation, public perception
          issues can outweigh the technical ones in terms of barriers to imposition. Key to
          this are the matters of  ownership and identity. Studies have demonstrated that
          people are generally prepared to reuse water if it derives entirely from their own
          household, i.e. if they know where it has been. They are rather less prepared to
          use  water  if  it  is  identified  as deriving  from  some  other  source  such as, for
          example, their neighbour’s house (Jeffrey, 2002). Curiously, the complete loss of
          identity, such as arises either from large-scale community schemes, and indeed
          from  conventional  water  supply  via  municipal  works  and  intermediate
          environmental water  bodies  such  as  rivers,  reservoirs  and  aquifers,  is  also
          perceived as being acceptable.
            In reviewing the water reuse opportunities in industry, it is important to make
          the distinction between reclamation  and recycling.  Reclamation  is the recovery
          and  treatment  of  water  to  make  it  available  for  reuse:  recycling  is  the
          recovery and reuse (whether or not subject to treatment) to and from a discrete
          operation. The development of water reclamation and reuse dates back centuries
          but modern  day legislation  probably  dates back  to  1956 in Japan, when the
          Industrial Water Law  was  introduced  to  restrict  the use  of  groundwater by
          the rapidly growing Japanese industry, and Californian legislation leading to the
          adoption of the Federal Water Pollution Control Act of  1972 (Cologne, 1998).
          The drive for conservation of  freshwater supplies has led to the development in
          some parts of the world, and in arid regions of  the USA  in particular, of  large-
          scale community schemes in which water “recovered” from a municipal works is
          directly used  for specific duties. In Japan, where sewerage services are limited
          and/or  expensive,  there  has  been  a  proliferation  of  in-building  recycling
          schemes. For all such schemes, the key to the successful implementation of  the
          reuse scheme is user acceptance and, ultimately, the assessment of risk.
            Risk  analysis,  specifically to  human  health  (Sakaji  and Funamizu, 1998),
          plays a key function in municipal or in-building reuse schemes because of  the
          implications  of  system failure for human health. Recycling  of  greywater  (i.e.
          water  used  for washing) within a  building, for  example, is  only  likely to  be
          acceptable if there is only a very minor risk to human health, predominantly
          from pathogenic microorganisms,  arising  from  failure  of  the reuse  system or
          some component of  it. This imposes a limit both on the required rigour  of  the
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