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