On a global level, wastewater treatment is an increasingly critical topic of discussion that has been addressed at the highest levels of government and major corporations. To find a sustainable approach, companies can employ many different strategies to help themselves go beyond mere compliance and begin the process of improving global water quality.
According to http://UN.org, more than 80 percent of all the wastewater from industry, homes, cities and agriculture flows back into the ecosystem via lakes, rivers and other bodies of surface water. This process repeats every day across the planet, polluting the environment while losing valuable nutrients and other recoverable materials in the process.
Each year in March, World Water Day serves as a reminder from the United Nations that a daily commitment is necessary for the successful reduction and reuse of wastewater. Guy Ryder, the director-general of the UN International Labor Organization (ILO) and the chairperson of UN-Water, believes that there must be a commitment to improve management of wastewater from the business community and the general public to make a difference.
With this commitment, Ryder hopes to achieve the UN’s 2030 Agenda for Sustainable Development, which targets halving the proportion of untreated wastewater and increasing safe water reuse by 2030. Often taken for granted, water is a finite resource with international demand. Wastewater treatment has become an ever-critical part of plant operations over the last decade, and manufacturing companies across all industrial sectors are prioritizing the reduction of water consumption.
Motivating factors for industrial wastewater treatment beyond compliance
Compliance with tightening federal regulations for wastewater treatment, handling and disposal, such as the Clean Water Act, the Resource Conservation and Recovery Act, and the Safe Drinking Water Act, requires plant management to be focused on the wastewater issue. Companies must adhere to additional regulations on the state and local level as well.
Additional motivating factors that are potential drivers for recycling wastewater include strengthening a company’s public image, improving the overall working environment, boosting employee morale, and adhering to ISO 14001 initiatives. Promoting a “green” operation by putting a priority on environmental awareness and sustainable operations will translate to happy workers, loyal customers and satisfied investors.
The dollars – and the sense
From a strictly monetary standpoint, it makes sense for companies to adopt a formal wastewater treatment and reuse policy because it allows them to dramatically cut rising operational costs while increasing profitability. Disposing of spent water-based coolant or wash water is expensive. Companies must pay for handling, trucking and treatment by their local publicly operated treatment works (POTW). Adding to the expense is the clean water required to replace the initial volume.
- Water disposal costs can vary based on:
- Local water supplies
- Fuel prices
- Trucking prices
- Edicts of the POTW
The obvious goal should always be to recycle coolant, wash water and other fluids internally. This will increase tool life, improve product quality, reduce maintenance, and prolong the usage of working fluids. Having a fluid-recycling process in place means when the time comes to dispose of wastewater and fluids, companies will have a lower volume to discard or a concentrated stream they can treat themselves for lower cost handling at the POTW.
While it certainly makes business sense to implement such a process, for companies that are unfamiliar with the treatment and reuse of in-house wastewater, it can appear to be a daunting task. On the surface, up-front costs often associated with adding a wastewater treatment system can seem prohibitive.
At the heart of any system is the equipment. For companies concerned about the effect their wastewater has on the environment and their bottom lines, a variety of options are available – each designed to perform specific types of treatment and deliver a quick return on investment (ROI).
Top industrial wastewater equipment, benefits and ROI
The following list includes the seven most common types of wastewater equipment, how each operates, and how it affects a business’s profitability:
1. Ultrafiltration systems
Ultrafiltration (UF) is a pressure-driven process that uses a membrane to remove emulsified oils, metal hydroxides, emulsions, dispersed material, suspended solids and other large molecular weight materials from wastewater, coolant and other solutions. UF excels at the clarification of solutions containing suspended solids, bacteria and high concentrations of macromolecules, including oil and water.
UF systems are designed to reduce oily water volumes by as much as 98 percent without the use of chemical additives. These systems are also capable of removing small fines in deburring and tumbling operations, which allows the water and soap solution to be recycled and reused. When calculating heating and disposal expenses, companies can also see a reduction of wash water and detergent costs by as much as 75 percent and a reduction in waste disposal costs by as much as 90 percent. For these reasons, UF membrane technology is quickly becoming the process of choice over conventional filtration methods.
2. Vacuum evaporation and distillation
Evaporation is a natural phenomenon and a clean separation technology recognized as a best available technique in several wastewater treatment processes. Because it removes the water from the contaminants, rather than filtering the contaminants from the water, it is distinct from other separation processes.
No other technology can attain such high water-recovery and concentration rates as vacuum evaporators, which accelerate the natural evaporation process to treat and distill industrial wastewater amounts from 1 to 120 tons per day. They are capable of achieving residual total solids concentrations of more than 85 percent.
The three primary vacuum evaporators are:
- Heat pumps – Flexible and versatile with low electrical energy consumption and superior reliability
- Hot water/cold water – Reduce operating costs by utilizing existing excess hot water/steam and cooling water
- Mechanical vapor recompression – Engineered for the treatment of large wastewater flow rates with low boiling temperatures for reduced energy consumption
3. Reverse osmosis systems
Reverse osmosis (RO) technology removes dissolved solids and impurities from water by using a semipermeable membrane, which allows the passage of water but leaves the majority of dissolved solids/salts and other contaminants behind. The RO membranes require a greater-than-osmotic pressure and high-pressure water to achieve the desired result. The water that passes through the RO membrane is called the permeate, and the dissolved salts that are rejected by the RO membrane are called the concentrate.
A properly designed and operated RO system can remove up to 99.5 percent of incoming dissolved salts and impurities, as well as virtually all colloidal and suspended matter from the most challenging waste and feedwater applications. Typically for industrial, metalworking and surface treatment applications, RO technology is the final process after UF or the chemical treatment of waste and feedwater.
4. Paper bed filters
These types of filters work by gravity and utilize disposable paper media or permanent filter media to produce a positive barrier, which removes solids from all free-flowing industrial process liquids. Paper bed filters are suitable for applications that involve low- to medium-stock removal of ferrous and nonferrous metals, as well as organic and inorganic contaminants such as glass, rubber and plastic. Paper bed filters can extend coolant and tool life by an average of 27 percent, in addition to increasing surface finish quality.
Standard paper bed filtration units are available with or without magnetic separation and can handle flow rates of up to 130 gallons per minute (gpm). Different classes of filter media allow for adjustments of micron clarity. A drum-type model, which can process up to 500 gpm of fluid, occupies one-third the floor space of a paper bed filter.
5. Solid bowl centrifuges
These units optimize centrifugal force (instead of consumable media) to separate solids from liquids in metal processing applications where removal of fines is important for recycle and reuse goals. Process liquid is either pumped or gravity-fed to the centrifuge inlet. Process solids are then centrifugally separated from the liquid phase and collected in an easily removable rotor, also known as a liner. Clarified liquid overflows the rotor into the outer case and is returned by gravity to the process, which minimizes the cost of hauling waste coolants and water away from the facility.
Solid bowl centrifuges provide high-performance liquid/solid separation for all types of particles – metallic and nonmetallic, ferrous and nonferrous – and are available in both manually cleaned rotor style (with a reusable liner) and fully automatic self-cleaning designs.
6. Tramp oil separators
In this wastewater treatment solution, contaminated fluid flows through a series of baffles and a porous media bed, during which free and mechanically dispersed oils are separated from the fluid. The clarified fluid then flows over the effluent discharge weir back to the reservoir for reuse. The collected oils, inverted emulsions and other waste materials are collected at the top of the separator and automatically discharged into a suitable receptacle. Using gravity flow and coalescence, these separators can reduce tramp oils to less than 1 percent in a single pass while utilizing no consumable products.
Tramp oil separators can also:
- Reduce new fluid purchase costs up to 75 percent (including synthetic and semisynthetic coolants, soluble oils and wash waters)
- Reduce the cost of wash water detergents, heating and disposal
- Reduce hazardous waste volumes up to 90 percent
- Achieve system payback (or ROI) in six months or less
7. Vacuum filters
Capable of continuous operation, vacuum filtration systems can eliminate significant downtime. Virtually maintenance-free and delivering high-sludge-volume elimination, these systems will also deliver lower production costs. Disposable media vacuum filters utilize a vacuum chamber to draw contaminated coolant through the disposable filter media. By applying the proven principle of optimal filtration through contaminate or sludge buildup, a filter cake forms on the media. These units are capable of impressive flow rates of up to 2,000 gpm.
Semipermanent vacuum filters can further reduce operation costs by eliminating the need for disposable media. Back-flushing with clean coolant keeps the filter clean without requiring large volumes of air. The back-flushed solids drop from the filter element and settle into a tank, where they are removed via a chain dragout/flight arrangement. These units require minimal floor space and are completely self-contained, simplifying maintenance and operation.
Considered an increasingly critical topic of global concern, wastewater treatment is something industrial manufacturing operations can address with any number of existing, efficient and effective systems. Companies can employ many different strategies to help themselves go beyond mere compliance and begin the process of improving water quality. This can simultaneously bolster their brand, their ROI and their bottom lines.
Tim Hanna is the vice president of business development for PRAB, a designer and manufacturer of wastewater recycling systems as well as engineered conveyors and equipment for processing turnings, chips and metalworking fluids. Since graduating from Northwood University in 1970, Hanna has worked closely with companies and communities worldwide that use the latest fluid filtration and chip-handling technologies to lower costs and increase environmental stewardship.