Wastewater charges (sewer bills) are based on water consumed at a facility, since most municipalities do not meter water exiting a facility. By minimizing water use, a facility can minimize both the cost of purchasing water and the cost of wastewater disposal. Therefore, in the case of wastewater, waste minimization consists of reducing the volume of water used.
Best Management Practices & Pollution Prevention
Waste Water Monitoring
In order to reduce wastewater generated, a facility must have a clear picture of the water used at their facility and potential areas for reduction. An important step in understanding a printing facility’s water use is determining the quantity of water being used in each process. 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. This may be divided into industrial water and sanitary water. Key usage points may include the primary incoming water line(s), any parts of the printing process that use large quantities of water, and the point(s) where industrial waste water enters into the sanitary sewer pipe (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 required.
The installation of water meters may also aid in resolving environmental compliance issues associated with industrial discharges of waste water. Sanitary water usage is typically minimal compared to industrial water usage and is generally not of concern in terms of environmental compliance issues. If this is the case, consider placing a water meter on the industrial water line only.
Waste Water Minimization
There are various measures available to reduce the wastewater volume created, such as installing flow restrictors on water lines, installing fan type spray heads, and using pressurized water for cleaning.
Additional water use minimization activities include:
- Scheduling print jobs with similar characteristics in a row, to minimize the number of times or number of print decks that must be cleaned between runs.
- 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 wastewater generated as a result of cleaning and relay this information back to plant personnel.
Since most facilities are charged for wastewater based on incoming water, they may be paying for water that is not discharged. This is the case if water is mixed within chemicals used for press cleaning and then collected as a hazardous or non-hazardous waste stream that is shipped offsite. 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 before cleaning.
- Clean press parts and ink trays immediately after coming off press to avoid ink drying. The longer the ink sits, the more cleaning will be required.
- Use detergents (caustic) and additives according to manufacturer’s recommendations to avoid excessive rinsing due to using too concentrated solutions.
- Thoroughly scrape press parts before any water is used for cleaning.
- Use low flow spray nozzles on hoses.
- Modify press cleaning activities to an organized multi-stage cleaning process to reuse waste water. (For more information see the Multi-stage Cleaning page)
Waste Water Treatment
A wastewater treatment system or filtration system may be necessary to meet local discharge limits. Additionally, some companies have found that filtered wastewater, depending on its degree of contamination, may be used to dilute inks when necessary, conserving water use.
For access to vendors who may supply alternative materials and equipment, see the PNEAC Vendor Directory.
An industrial wastewater discharge permit may be required by state or local regulations.
If a waste water treatment system is installed an operating permit and operator's license requiring special training may be required.
By minimizing water usage, the concentration of contaminants may increase. Review local, state and federal discharge regulations and test water to assure continued compliance.