Water Management
The School for Resource and Environmental Studies, Dalhousie University
Background
Two things make water a unique natural resource:
Water is essential for human survival.
The total amount of water in the world is constant and can neither be increased nor diminished.
Industry is the largest user of water resources and the most important source of harmful pollution globally. Effective water management programs must be established for the efficient use and reuse of this natural resource.
End-of-pipe treatment bears a direct relationship to the volume of wastewater to be treated and to the concentration of pollutants contained in the discharge. Reduction of emissions by action at the source can have a significant impact on the size and hence cost of an end-of-pipe treatment system. If efforts are made in water management programs to increase reduction, reuse, recycling and recovery then it follows that lower effluent discharges would result. This section summarizes various options that can be used to minimize wastewater.
Implement preventative measures to recover spillage and detect leakage.
Increase employee water conservation awareness.
Reuse clean or contaminated water where possible.
Measure water inflow and outflow rates from each unit process to control water usage.
Control water to specific requirements and install flow control valves.
Use countercurrent rinsing techniques.
Reduce frequency of plant cleaning.
Separate clean cooling water and uncontaminated clean rainwater from wastewater flows.
Install drainboards and dragout tanks to recover dragout losses.
Use high-pressure washing equipment to reduce the amount of waste water generated.
Equip rinse tanks with flow control valves.
Agitate rinse baths to reduce water consumption.
Install water-saving sanitary fixtures.
Use metal recovery technologies or evaporators to facilitate recycling and reuse of rinse waters.
Use a centrifuge or filter press to dewater sludge and reduce disposal costs.
Replace undesirable substances with those more environmentally friendly in character.
Modify manufacturing processes to produce less polluting effluents.
Questions to Ask?
Incoming Water
What quantity and quality of feed water is required for each unit operation?
What sources of water are available on site? Are they of suitable quantity and quality?
What pretreatment may be required? Is the existing pretreatment system operating at its best? Can savings be made by using alternative equipment or operating procedures?
Has the demand pattern changed recently or is it likely to do so in the future?
Production Operations
Can excessive demand peaks or washes be avoided or reduced.
Identify the pattern of water use for each separate unit process. Is the water over-treated prior to use? Can lower grade water be used satisfactorily?
Identify the pattern of waste generation for each separate unit process. Why is it generated? Can it be reduced or eliminated?
Wastewater
Is it possible to segregate waste streams at source?
How does the cost of increasing the degree of treatment compare with charges arising from effluent discharge to sewer or watercourse?