Most sewer bills, charging the facility for their wastewater treatment, is based on the amount of water consumed at the facility. Most municipalities do not meter the wastewater exiting the facility. They only meter the water coming in and base a water and sewer bill on this measure. A facility may be paying for waste treatment that is not taking place. An example would occur in facilities where less water is exiting the facility than what came in as a result of wastewater recycling and reuse, off site disposal, or other activities.
By minimizing water use, a facility can minimize both the cost of acquiring water as well as the disposal of contaminated process wastewater disposal. Waste minimization consists of reducing the volume of water used in the first place and reusing the water that is consumed. Of the two approaches, source reduction is usually considered preferable to recycling from an environmental perspective.
Best Management Practices & Pollution Prevention
It is useful to determine where and how much water is being used. Develop a plant water diagram (flow chart of water usage) and water balance (how much in/out) that is periodically reviewed, updated and used to develop further conservation methods. Use the diagram to develop a written water conservation program that utilizes elements given below that apply to your facility.
Ideally, install water meters at key usage points in the plant and take readings at regular intervals (first of month & end of month) to account for all water used. Key usage points may include the primary incoming water. This may be split into industrial water and sanitary water.
The installation of water meters may also aid in resolving environmental compliance issues associated with industrial discharges of waste water should they arise. Sanitary water usage is typically minimal compared to industrial water usage and is generally not of concern in terms of water usage and wastewater discharge environmental compliance issues. If this is the case, consider placing a water meter on the industrial water line only.
Other key usage points may include the point where industrial waste water enters into the sanitary sewer (as long as this is on the printer’s property). If the sanitary and industrial waste water combine into one pipe prior to discharging into the sanitary sewer a water meter installed upstream of this connection to measure the flow of industrial waste water may be in order.
Waste Water Minimization
In order to reduce the volume of waste water that must be treated, various measures such as installing flow restrictors on water lines, installing fan type spray heads, using pressurized water for cleaning will help minimize the amount of water consumed.
Additional water use minimization activities include printing job scheduling to minimize the number of times or number of print decks that must be cleaned at the end of a run by scheduling jobs back to back that print like colors.
Form a multi-disciplinary water conservation team to review all facets of plant operation to develop a plant water budget that is tracked and followed. Determine the costs associated with the volume of waste generated as a result of cleaning and correlate this back to plant personnel. An example would be to explain their company profit sharing benefits being reduced as a result of high waste disposal costs.
Multi-stage cleaning processes involve semi-dirty water (previously interim rinse water) to remove the first layer of ink and soil on the press and press parts. Then utilizing water recovered from the previous final rinse to be used in the interim or middle stage of the cleaning process. And finally using fresh water for final rinse of the press and press parts.
Fresh Water from Final Rinse → Water from Previous Final Rinse → Dirty Water for Initial Rinse
The amount of water used in the cleaning process can be reduced by training press operators to:
Drain as much ink as possible into containers.
Clean press parts immediately after coming off press to avoid ink drying. The longer the ink sits will increase cleaning efforts required.
Use detergents (caustic) and additives according to manufacturers recommendations to avoid excessive rinsing due to using too concentrated solutions.
Thoroughly scrape press parts before any water is used for cleaning.
Increase cleaning efficiency by cleaning ink stations promptly (before the ink begins to dry).
Use low flow spray nozzles on hoses.
Use water flow restrictors.
Modify press cleaning activities to an organized multi-stage cleaning process to reuse waste water.
Waste Water Treatment
A wastewater treatment system or filtration system may be cost effective in reducing waste disposal costs. Some companies have found that filtered wastewater, depending on its degree of contamination, may be used to dilute inks when necessary.
For access to vendors who may supply alternative materials and equipment, see the PNEAC Vendor Directory.