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SPDES Permitting of Water Treatment Chemicals (WTCs)

Many industrial, municipal and private/commercial/institutional facilities use and discharge WTCs. WTCs are chemicals that are added to water to modify its properties or to interact with other substances that are either in the water or that the water is in contact with. WTCs are perhaps best defined by reviewing examples, which include: biocides, coagulants, conditioners, corrosion inhibitors, defoamers, deposit control agents, flocculants, scale inhibitors, sequestrants, and settling aids.

Water quality issues associated with WTC use

WTCs often contain ingredients which have the potential to harm water quality. In response, the Department has developed ambient water quality criteria for a number of these chemicals. However, there are many more of these chemicals which have not been evaluated by the Department. An additional challenge is that there are few approved analytical methods available to verify WTC discharge levels. For surface water discharges, aquatic toxicity testing data can serve as a partial surrogate for the lack of ambient water quality criteria and analytical methods.

Department procedures in place to prevent water quality problems - the WTC Authorization Form

In accordance with Department regulations, 6 NYCRR Parts 750-2.6(a) & 750-2.9(a)(1), new or increased use and discharge of a WTC requires prior Department review and authorization. At a minimum, the permittee must notify the Department in writing of its intent to change WTC use by submitting a completed WTC Authorization Form for each proposed WTC. The Department will review the submitted information and determine if a SPDES permit modification is necessary or whether WTC authorization may proceed without a formal permit modification. The majority of WTC authorizations do not require SPDES permit modification. Department staff may also direct a permittee to use this form for review and authorization of other chemicals which may be present in the wastewater.

WTC Notification Form (PDF, 72 KB)

Instructions, exceptions and additional information concerning the form are available here.


Permittees are required to maintain a logbook of all WTC use, noting for each WTC the date, time, exact location, and amount of each dosage, and, the name of the individual applying or measuring the chemical. The logbook must also document that adequate process controls are in place to ensure that excessive levels of WTCs are not used and subsequently discharged through outfalls. The permittee shall retain the logbook for a period of at least 5 years in accordance with 6 NYCRR Part 750-2.5(c)(1).

Annual Reporting - the WTC Annual Report Form

Permittees that use and discharge WTCs are required to submit an annual summary using the WTC Annual Report Form, each year that they use and discharge WTCs. The permittee must summarize all WTC use for the prior calendar year, January 1 thru December 31, and attach it to either the December Discharge Monitoring Report (DMR) or the annual monitoring report required by the SPDES permit.

WTC Annual Report Form (PDF, 52 KB)

More about SPDES Permitting of Water Treatment Chemicals (WTCs):

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