INTRODUCTION
Reuse water can be defined as used water that can be recycled for cooling, boiler or process applications. It may be treated to remove contaminants that will cause problems in that application. This treatment may be simple or very extensive. Certainly, water short areas (or plants) may have a higher priority than cost to make water available for plant applications. Each facility must determine its own priorities for water reuse. Thus, water reuse is site specific.
To successfully reuse any used waters, it is necessary to first establish the requirements (or purity) of the water needed for that specific application. If the used water constitutes a small percentage of all waters to be used, the combined water quality must be considered.
Matching water quality with water-using equipment requirements is the key to successful reuse.. Using a used water without proper pretreatment will almost always result in unsatisfactory results. This lack of success often results in excess or premature damage to the water-using equipment and excessive treatment costs. Economics often will dictate how much treatment should be performed of a specific used water. Thus, knowing your equipment requirements is extremely important in successfully reusing used waters.
Treated municipal waste water, most often defined as reclaimed water, has seen substantial reuse during the past IO+ years to replace fresh waters. Reclaimed water use has expanded to many plants - specifically utility, power, petroleum refinery, petro-chemical, chemical, cogen, automotive, electronics, and even commercial and institutional facilities.
RECLAIMED WATER QUALITY
Reclaimed water can be characterized as to quality, though variations can be considerable. This depends upon the water quality of the surrounding area in addition to the municipal waste water treatment. Typical water quality often is:
Specific water characteristics common to reclaimed waters are the phosphate, ammonia and organic contents (total COD, BOD and TOC). These parameters can be beneficial (phosphate, nitrate) or detrimental (ammonia, silica, total dissolved solids) depending upon the water systems utilizing this reclaimed water. Further treatment (such as softening, clarification, nitrification, etc.) can produce a water of very good quality.
When high total dissolved solids are present horn chlorides, sulfates, fluorides, nitrates, etc., treatment by reverse osmosis may be required for some users who need lower dissolved solids.
