The physical and chemical characteristics of the discharge were submitted; and based upon these
factors and the parameters of the receiving stream, the EPA determined how much, if any, heavy
metals could be contained in the discharge. Since the Act was passed into law, most states have
adopted similar procedures for discharge into interstate waterways. More recently, the Federal
EPA imposed a complete ban on the use of hexavalent chromium in comfort cooling towers (40
CFR Part 749 1/2/90). (3)
Subsequently, the introduction of organophosphorus compounds arrived. Organoposphours
compounds do not breakdown like inorganic polyphosphates except under severe
microbiological attack.
In the past, cooling water chemistry and operating parameters were analyzed by using grab
samples to optimize cooling water system operation by adding inhibitors to inhibit piping and
exchanger corrosion, by adding dispersants to minimize solid precipitation, and to control
microbial growth by adding oxidants. The cooling system is monitored based on manual
sampling and laboratory results. Most of the NPDES and wastewater permits required only
infrequent grab samples for reporting purpose for pH, temperature, TSS, O&G, and COD at the
blowdown or outfall. Continuous monitoring systems were seldomly used. However, online
testing and sampling approaches are quickly becoming recommended, as they become more
technologically available.
4.
History of Regulations and Monitoring
Air emissions from cooling towers are regulated under a number of different federal laws. These
laws have resulted in regulations that can require certain monitoring, air pollution controls, work
practice standards, and permitting requirements for cooling towers.
During an air permitting review, the cooling tower VOC emission is required to use EPA-AP-42
emission factor for Refinery industries of 0.7 lb/MMgal of recirculating cooling water to
calculate the total VOC emission if the plant does not have any acceptable specific actual plant
test data. For a large cooling tower, the VOC estimate could be a very significant contributor of
the total plant wide VOC emission and may be required to be verified and make corrections after
a test program identifies the true baseline level of emission during plant operation. Some of
these laws and the resulting regulatory requirements are identified below:
Prevention of Significant Deterioration (PSD) Permits: The PSD permit program originated
from the 1977 Clean Air Act Amendments. The PSD program is a permitting program for large
new, modified, or reconstructed sources in clean air areas (areas that are in compliance with
National Ambient Air Quality Standards [NAAQS]). The PSD program was intended to protect
the air quality in these areas, while allowing some industrial growth and expansion.
For large new, modified, or reconstructed sources, the emissions from all sources must be
evaluated, including cooling towers. Cooling towers emit PM10 and VOC's (or HAPS) and if
included in a PSD review, these emission sources would be required to: (1) Install Best
