Environmental Protection

ABCs of CWT

Centralized waste treatment: the guidelines for treating liquid wastes and how they affect you

As a part of the Clean Water Act, the U.S. Environmental Protection Agency (EPA) is required to provide effluent guidelines to particular industries, whether they discharge wastewater to surface water or publicly owned treatment works (POTW). For example, steel mills, paper mills and laundries each have their own effluent guideline. One of the more recent categories added to this list is the “Effluent Limitations Guidelines and Pretreatment Standards for the Centralized Waste Treatment Industry.” Effective December 22, 2003, these regulations changed the way liquid wastes are categorized, and created new treatment requirements for waste delivered to a centralized waste treatment (CWT) facility based on those categories. A CWT facility is a wastewater treatment plant that has a permit to accept industrial wastewater from separate offsite companies, treats those wastes, and discharges the ensuing effluent to a POTW or a surface waterway. These rules affect all U.S. CWT facilities. EPA has estimated that there are 233 CWT facilities in the United States; 165 of these discharge wastewater.

How It Affects Industry
This regulation put the burden back on industry to ensure environmental compliance and corporate responsibility. It has prompted industries to enlist CWT providers for assistance with compliance requirements. For some industrial customers, a simple cost analysis of their waste disposal may point them to a CWT provider. Industries must ask four basic questions when searching for a CWT provider: Who is permitted to accept the waste? In what form is this waste accepted, and at what quantity? Does this CWT provider have experience with this type of waste? What type of treatment technologies are used to treat this waste? In addition to these considerations, the industrial customer is often looking for a provider who can also pick up the waste and ensure its proper transportation and treatment.

What is the Process?
The CWT process is fairly simple. The CWT provider asks the customer to complete a waste acceptance profile. This document requires three important pieces of information: the name of the generator, what it does, and a process description of the waste (where the waste comes from). The provider may ask for a sample of the waste in order to conduct an approval analysis and a treatability study to determine the treatment method.

CWT guidelines provide provisions for different types of wastes. The regulation splits wastes into four subcategories. Each CWT facility is permitted to accept and discharge specific subcategories based on available treatment technology. According to the EPA’s Small Entity Compliance Guide, the four subcategories of waste are:

• Subcategory A – Facilities that treat or recover metal from metal-bearing waste, wastewater or used materials received from off site.
• Subcategory B – Facilities that treat or recover oil from oily waste, wastewater or used materials received from off site.
• Subcategory C – Facilities that treat or recover organics from organic waste, wastewater or used material received from off site.
• Subcategory D – Facilities that treat or recover some combination of metal-bearing, oily or organic waste, wastewater or used materials received from off site.

A CWT facility must determine how to categorize the waste when a sample is received. If the waste comes from a list of common sources, that characterization has primacy. Failing that, if the waste contains significant oil, it will be in the oil subcategory. Failing that, if it contains significant metals, it will be in the metal subcategory. Those wastes that do not contain oils or metals, but fall under the CWT requirements, will be placed in the organic subcategory. Mixtures may be placed in Subcategory D.

Wastes for each subcategory originate from a variety of sources. The wastes from the metals subcategory, for example, can include metal finishing rinse waters and sludges, cyanide-containing wastes, spent electroplating baths and incineration wastewaters. Oily wastes can come from oil spills, off-specification fuels, bilge water, aqueous and oil mixtures from parts cleaning operations, to name a few. The organics subcategory includes sources such as landfill leachate, still bottoms, wastewater from organic chemical product operations, solvent-bearing wastes, and other wastes not characterized as oily or metal bearing.

Treatment Technologies
EPA bases the effluent technologies for each waste subcategory on the technologies shown in Table 1. It does not monitor the CWT facility’s treatment processes as long as it meets the minimum discharge requirement set by the local, state and federal guidelines.

(**Cheryl, I’ve requested that the marketing contact resubmit this table to us in a tif or jpeg format.)

Table 1 Technology Basis for the Final CWT Limitations for Existing Facilities
Subpart Name of Subcategory Technology Basis
A Metal-Bearing Waste Treatment and Recovery (metals) Batch Precipitation, Liquid-Solid Separation, Secondary Precipitation, Clarification, Sand Filtration, Ion exchange, Ultrafiltration and Reverse Osmosis. For Metal-Bearing Waste that Includes Concentrated Cyanide Streams: Alkaline Chlorination in a two step process
B Used/Waste Oil Treatment and Recovery (oils) Emulsion Breaking/Gravity Separation, Secondary Gravity Separation and Dissolved Air Flotation
C Organic Waste Treatment (organic) Equalization and Biological Treatment
D Combination of A, B, and C Treatment strategy: required to use all of the above (A, B, C) or a treatment strategy certified to be equivalent.

Benefits of Partnering with a CWT Provider
While industries that produce waste are required to follow the guidelines, CWT facilities can partner with these businesses to ensure that the process is seamless and worry-free. The Association of Responsible Recyclers (NORA) and its member businesses are committed to sound environmental policies, high standards of integrity and continual improvement. By partnering with a NORA member business for CWT, industries are assured that their CWT provider follows the highest standards.

An example of a customer partnership is an alliance between Siemens Water Technologies and a major east coast shipyard. The Siemens branch in Wilmington, Del., has treated roughly 12.5 million gallons of water originating from this shipyard in the past seven years. Before a ship can be sold or used for reefing, it must have the fuel and bilge waters removed. This work includes recovery of 50,000 to 500,000 gallons of bilge water and petroleum products from ship tank cleaning, line cleaning, and gas-free certification, all managed as a turnkey service. CWT compliance allows Siemens to efficiently provide this service.

Another example is a large power company on the east coast, from which Siemens’ CWT facility has received approximately 3 million gallons of water to be treated in the last three years. This contaminated water is obtained from manhole pump-outs throughout the city of Philadelphia, and must be treated before discharge.

Many manufacturers in the semiconductor, electroplating and metal finishing industries have been able to comply with their wastewater discharge requirements by using ion exchange for metals recovery. Ion exchange is a safe, reliable and environmentally friendly way to remove metals such as copper, nickel, zinc and lead from industrial wastewater. Portable vessels containing ion exchange media are used to remove these metals from the manufacturer’s wastewater. This resin must be exchanged when the media becomes saturated with metals.

A CWT provider can supply an ion exchange service where spent tanks are removed and replaced with tanks containing fresh media. This allows manufacturers to discharge the ion-exchange-treated wastewater to their local wastewater treatment plant without worry that they will exceed industrial discharge permit limitations for regulated metals. Alternatively, manufacturers can reuse the treated water in their process, thus lowering water use and discharge costs.

For example, a Midwest manufacturer of ice cube making machines sends their waste to a CWT provider who recovers metal from a spent nickel bath generated by the refrigeration coil plating process. The provider is a Siemens centralized treatment and recovery facility (CTRF), operating in compliance with CWT regulations. Nearly 100,000 gallons a year of this nickel waste is shipped to the facility, which treats the waste and recovers the nickel.

Another example is a very large microelectronics manufacturer in the Dallas, Texas, area who uses ion exchange tanks from Siemens to treat dilute copper-bearing waste streams. When the ion exchange resin is depleted, the tanks are sent to Siemens’ CTRF, where the resin is treated and regenerated for copper recovery. The tanks are then filled with freshly regenerated resin and sent back to the customer. This same customer generates other copper-bearing waste streams that are too concentrated to be treated with ion exchange. In this case, the concentrated copper-bearing waste streams are sent via tanker truck to Siemens for treatment and copper recovery.

Siemens offers this service through its Roseville, Minn., facility, which maintains an EPA Resource Conservation and Recovery Act (RCRA) Part B permit to handle hazardous and nonhazardous wastes. Service centers are maintained throughout the country for tank supply and pickup as well as system maintenance. Metals removed with ion exchange can be recovered, and returned to commerce and used to manufacture new products. This keeps them from being disposed of in a landfill, so that these valuable commodities can be reused in commerce, pollution prevention goals are met and the generator’s liability for future waste cleanup is minimized.

Spent carbon media are returned to Siemens’ RCRA Part-B permitted storage, treatment and recovery facility for regeneration and replacement. A high-temperature metal recovery process recovers metals such as zinc, lead and cadmium. The process uses a kiln at high temperature under conditions that cause some metals, like zinc, to vaporize and be separated from other metals in the waste. Metals that remain after the separation are bound in an iron-rich matrix. In addition to metal recovery, waste carbon and other single-use media replace raw materials that would otherwise need to be purchased to operate the high-temperature metal recovery process.

Diligence on the part of the CWT-qualified wastewater treatment provider ensures environmentally acceptable treatment of a company’s aqueous liquid wastes. By partnering with an experienced provider, a company can realize greater consistency and economic efficiency, with a positive result to the bottom line.

Preparing a CWT Facility to Meet the Regulations

Facilities at Siemens Water Technologies prepared to meet CWT regulations by making changes to the facility and aligning the various waste streams accepted by the facility into the various categories. It took approximately 18 months to prepare for the December 2003 implementation of the CWT regulations.

Preparation for facility operations included:
• Determination of category applicability and standards to be met
• Development and validation of suitable analytical methodologies
• Comparison of current treatment system performance to CWT requirements
• Performance of bench scale testing to verify treatment performance against category requirements
• Determination of needed equipment and process changes
• Determination of requirements for permitting process changes required to achieve compliance

The results of the research and testing were assembled and reviewed by Siemens engineering, environmental compliance and operations staff in conjunction with the local agencies. A timeline and operating plan were finalized.

As part of the facility preparation, and in order to meet the time constraints after implementation, Siemens reviewed the existing waste streams. Thousands of distinct waste streams were categorized using electronic data analysis, as well as a thorough review of hard copy records. Customers were notified well in advance when the category assigned impacted the way the waste was managed or changed the pricing. This minimized any disruptions to the customers’ businesses.


The following general procedure is used to evaluate and accept wastes at the CWT facility:

• Pre-acceptance consists of characterizing the waste to make an initial determination of acceptability, CWT category and proposed management.

• Acceptance consists of activities to confirm that the waste delivered to the facility is as identified on the accompanying waste shipment documentation. At the end of the acceptance stage, the waste is received and accepted for further handling.

• Post-acceptance consists of those activities performed to properly manage the hazardous waste within the facility (i.e., compatibility testing).

• Waste management consists of the sampling and analysis necessary to properly treat and handle the wastes within the facility.

• Waste disposal consists of the activities necessary to consolidate, characterize and prepare hazardous waste for shipment and disposal to an approved third-party hazardous waste disposal facility.

• Liquid discharge sampling is the sampling necessary to ensure that the treated water is acceptable for discharge to the POTW.

This article originally appeared in the 07/01/2007 issue of Environmental Protection.

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