The New Chapter 92a Regulations Ratchet Down NPDES Discharge Standards Again
by Randy Hurst
In 1972, the Clean Water Act established national policies and goals to enhance and protect our nation’s waters. The primary national goal was “that the discharge of pollutants into the navigable waters be eliminated by 1985.” An interim goal of what became known as “fishable, swimmable” waters, was to be achieved “wherever attainable” by July 1, 1983. A national policy was that “the discharge of toxic pollutants in toxic amounts be eliminated.” 
Probably the most prominent creation of the Act was the National Pollutant Discharge Elimination System (NPDES) permitting program and the so-called “delegation” of that program to the states. Hence, for the last forty years the goal of the Clean Water Act has been to eliminate the discharge of pollutants. While the implementation of water quality-based discharge limits seems generally to have eliminated the discharge of toxic pollutants in toxic amounts as planned, the discharge of other pollutants continues some twenty-five years after the deadline for elimination.
Several provisions in the Act call for a gradual “ratcheting down” of discharge standards. Of particular interest in this respect is the concept of “technology-based effluent limits,” or TBELs. Applicable to industrial dischargers through Effluent Limitations Guidelines (ELGs) for the forty or so so-called “categorical” industries, and to publicly owned treatment works (POTWs) through the “secondary treatment standards,” the innovative concept of TBELs served to standardize wastewater treatment, resulting in discharges that, in most cases, are significantly “cleaner” than necessary to meet established water quality standards-a substantial step toward the goal of discharge elimination. For some industrial categories, TBELs have already implemented that goal by setting “no discharge” as the allowable limit. For POTWs, however, the TBELs that were established in the 1970s have not changed and the discharge of “conventional” pollutants, nutrients, and some others continues, even though treatment technology and the skill of treatment plant operators have measurably improved.  While EPA continues to evaluate potential new categories of industry for development of ELGs and revisits existing categories to determine if new technologies justify more stringent standards, no such program has been implemented to evaluate secondary treatment standards.  From time to time, environmental groups propose additional or more stringent secondary treatment standards, but EPA has not acted on these proposals.
Another relevant aspect of discharge standards under the Act is the concept of “narrative” standards. That is, in place of measurable numeric values, a more or less subjective standard is used. Probably the most ambiguous example familiar to Pennsylvania practitioners is the Maryland standard for chlorophyll α , which was used in part to impose over a billion dollars in treatment plant improvement costs on over 180 Pennsylvania POTWs under Pennsylvania’s Department of Environmental Protection (PaDEP’s) Chesapeake Bay Initiative.  Narrative standards can be useful, but depending on how well they are defined, can pose enforcement problems. In Pennsylvania, the NPDES regulations included a narrative standard prohibiting the discharge of “floating materials, oil, grease, scum, foam sheen, and substances which produce color, taste, turbidity or settle to form deposits in concentrations or amounts sufficient to be, or creating a danger of being, inimical to the water uses to be protected or to human, animal, plant or aquatic life.” 
With no progress by the EPA on tightening secondary treatment standards, some states have taken the initiative to do so on their own. PaDEP took a small but significant step in this direction in 2000 with revisions to its Chapter 92 regulations.  Although adopted under the rubric of the “regulatory basics initiative,” which was intended to be a process of simplifying regulations and eliminating those which were more stringent than EPA’s, the 2000 rule changes made secondary treatment standards more stringent. Those changes added numerical discharge standards for total residual chlorine and fecal coliform bacteria and attempted to add standards for pH and oil and grease.  These relatively modest additions generated little opposition since most POTWs could readily meet the more stringent standards.
In 2009, PaDEP proposed additional changes to Chapter 92, now to be completely reorganized and readopted as “Chapter 92a.” Among the proposed changes were a further “ratcheting down” of TBELs for POTWs, including a more stringent definition of secondary treatment and a radical change to the narrative discharge standards, both of which were adopted (with minor changes) in the final rulemaking.  Because these new rules have the potential to make NPDES permits issued to both POTWs and industrial dischargers impossible, or at least impossibly expensive, to meet, all permittees should be aware of them and prepare to address them when their permits are renewed.  The following discussion only addresses new and more stringent TBEL provisions; other changes to the rules are outside the scope of this article.
Secondary Treatment Standards
Most of the changes to secondary treatment standards are relatively minor. The revised rules impose the following new and more stringent standards for POTWs:
Physical/chemical treatment may not be used unless in concert with “significant biological treatment,” which is defined as “the use of an aerobic or anaerobic biological treatment process . . . to consistently achieve a 30-day average of at least 65% BOD removal.” See § 92a.47(a). The practical ramification of the rule is difficult to predict, but it will likely mean that some wet weather high flow treatment processes using ballasted flocculation (which by itself meets federal secondary treatment standards) may have to be re-designed to include some level of biological treatment under PaDEP’s unique and more stringent definition of secondary treatment.
The standard for effluent fecal coliform has been made more stringent. The prior “swimming season” (May-September) standard of a monthly geometric mean of 200 cfu/100 ml has been retained but the maximum of “no more than 10% of the samples greater than 1,000” cfu/100 ml (which was based on scientific principles related to bacteriological testing as reflected in the similar Chapter 93 Bac1 water quality standard of no more than 10% of samples greater than 400) has been replaced by a maximum any time (aka “instantaneous maximum”) standard of 1,000. In addition, an entirely new October-April standard of 2,000 as a mean and 10,000 as a maximum has also been created. Some POTWs reportedly worry that they will have to increase the chlorination rate in order to ensure full compliance with their NPDES permits under the new standard. This, in turn, may implicate some NPDES permits that contain a vague narrative “chlorine minimization” clause inserted by certain regional offices.
The federal “equivalent to secondary” standards for certain treatment technologies (lagoons and some trickling filter plants), which have more lenient C-BOD and TSS removal rates and relaxed effluent standards for C-BOD and TSS  have been eliminated. However, the new rules also provide that this “ratcheting down” will not be imposed on existing facilities with current permits reflecting the federal standards until the facility’s WQM permit is amended to allow an increase in the design flow. See § 92a.47(f).
The oil and grease standards for industrial dischargers (30 mg/L in any sample, 15 mg/L as a daily maximum), improperly adopted in the prior rules as noted above, have now been properly adopted and are enforceable, as are the pH limits of 6-9. See §§ 92a.47(a)(7) and 95.2(1), (2). As discussed below, however, the numerical oil and grease standard creates an internal inconsistency in the regulations that will require attention on a permit-by-permit basis.
Older POTWs with combined sewers will be pleased to note that the federal standard for allowing a lower “dry weather” percentage removal of C-BOD and TSS was not changed. Similarly, the federal standard allowing a lower percentage removal in separate sanitary systems with dilute influent was not changed in the new PaDEP rules. 
Probably the most worrisome change in the new regulations for POTWs and industrial treatment plants is the elimination of the rather vague narrative standards for foam, floating materials, etc. discussed above and the creation of a new two-tiered system of regulation. According to the Preamble to the Proposed Rulemaking, 40 Pa. Bull., 852, February 13, 2010, the change was prompted by the fact that the previous, water quality-based narrative standard (“inimical to the water uses to be protected”) was “too cryptic and nebulous to be useful.” Id. The new § 92a.46(c) revised the standard to an ostensibly technology-based one, but the change seems merely to have replaced one question with a host of new ones and promises to be a source of substantial cost and compliance headaches for many POTWs.
The new provision is written in two parts. The first sentence says that a discharger “may not discharge floating materials, scum, sheen, or substances that result in deposits in the receiving water.” Although still ostensibly a narrative standard, it is in fact numerical: the standard is now effectively “zero.” It is apparent that this new “zero discharge” requirement will result in the need for many, if not most POTWs and industrial dischargers to install skimmers or other specialized equipment to reduce normal environmentally inconsequential amounts of “scum” and “sheen” to undetectable levels. Additionally, since the terms are not defined, compliance issues may arise as PaDEP inspectors attempt to interpret the rules under specific circumstances. Finally, there is the compliance question regarding the inherent conflict between the secondary treatment standard for total suspended solids (45 mg/L as a maximum weekly average) and the prohibition on the discharge of settleable solids. A discharger meeting the secondary treatment standard may, nevertheless, find that it is in violation of the new narrative standard, especially when the receiving stream is relatively quiescent, as many are during low flow summertime conditions.
It may be the second part of § 92a.46(c) that will create the most turmoil, though. This provision states “[e]xcept as provided for in the permit, the discharger may not discharge foam, oil, grease, or substances that produce an observable change in the color, taste, odor or turbidity of the receiving water.” This new standard raises a series of questions:
Where in the receiving water is the change to be observed? That is, since discharges into most waters produce a widening “plume,” any color, turbidity, and foam rapidly dissipate as they move downstream, so the selection of the point to make the determination of an “observable change” can be the difference between compliance and multiple permit violations. PaDEP has established a standard for measuring compliance with water quality standards for toxic substances using a fifteen-minute mixing zone for acute water quality criteria, and a twelve-hour mixing zone for chronic water quality criteria. Although the new regulation clearly applies the color and turbidity standards somewhere in the receiving water, it makes no mention of where in the stream the inspector (or the concerned discharger) is to look. (Although, see the discussion below regarding permit limits for foam for some guidance on that particular constituent.) It would seem reasonable to assume that if mixing is appropriate for “serious” pollutants like toxics, it is also appropriate for purely aesthetic concerns like color and turbidity. However, the regulation does not reflect that logic.
What is an “observable change”? While oil and grease, color, and turbidity can be analyzed in the laboratory to produce numerical results, a difference in test results is not necessarily equivalent to an “observable change.” For instance, if a discharge increases the stream turbidity from 80 to 85 NTU, can that difference be observed, especially in a moving and turbulent receiving stream? Moreover, discharge plumes can sometimes be easily observed in receiving waters simply because of their different density-not color or clarity-making the determination of what, exactly, is being “observed” another potential point of debate.
What about the secondary treatment standard for oil and grease? As noted above, the regulations adopt the Chapter 95.2(2)(ii) discharge standards of 15 mg/L as a daily average and 30 mg/L in any one sample. If a discharge meets this standard, but oil and grease is nevertheless “observable” in the receiving stream,  is the discharge in compliance or not?
The solution to these regulatory conundrums appears to lie in the phrase “except as provided for in the permit.” That is, since nearly every POTW and industrial discharger will have some level of oil and grease, foam, turbidity, and/or color in its effluent, and since the new standard is technology-based, the risk of violations (or the uncertainty of what constitutes a violation) can be addressed by incorporating specific provisions in the NPDES permit reflecting the capabilities of the treatment plant. Permittees should be prepared to discuss the following issues with the PaDEP permitting staff during the development of the permit:
For oil and grease, the secondary treatment standard obviously should be in the permit. The question then becomes whether or not to actually conduct effluent testing for this parameter and, if so, how often. Perhaps that question could be more easily answered if some effluent data were available to demonstrate the risk of exceeding the limits. The testing conducted as part of the permit renewal application process may be a good opportunity to develop these data. Hence, managers and consultants should be prepared to conduct additional effluent testing for oil and grease in the hope of avoiding extensive compliance testing throughout the five year life of the permit.
For color there is a statewide water quality criterion in Chapter 93 (75 Pt-Co units) applicable to streams used for potable water supplies. Since PaDEP routinely generates the effluent/stream dilution ratio in its permit review, an appropriate effluent color limit should be calculable once the compliance point in the stream is determined. For some dischargers, pre-application effluent testing for color may be worthwhile to see if a higher TBEL is appropriate.
While turbidity can be measured, there is no numerical water quality criterion for it, so an empirical approach seems to be necessary. It would seem prudent to conduct some representative sampling of the effluent to establish a normal effluent turbidity baseline to use as a basis for proposing an appropriate permit limit. Averages are probably not appropriate as permit limits: obtaining sufficient data to estimate the level at two standard deviations above the mean (probably at least ten samples, possibly more depending on variability) would be prudent to avoid suggesting a turbidity limit that will be violated half of the time.
Leaving the issue of effluent odor and taste for another day, this leaves foam.  Of course, there is no standard for measuring it and no water quality criterion except for the legacy provision in Chapter 93 that it (along with the other substances) “must be controlled” to avoid “amounts sufficient to be inimical or harmful to the water uses to be protected or to human, animal, plant or aquatic life.” Like grease, virtually any amount of foam would be “observable” because of its light color and the fact that it floats. However, small amounts of foam are clearly not harmful (in fact, foam occurs naturally in many healthy streams due to naturally occurring organic matter). To avoid a “no discharge” permit limit, it would be prudent to propose some sort of measurable TBEL based on treatment plant performance so that both the operating staff and PaDEP inspectors can determine and agree on compliance status. There is some guidance for this in the Preamble to the Proposed Rulemaking, 40 Pa. Bull. 852, which states, “foaming would still be an unacceptable condition if the foaming is visually objectionable or persists for any distance away from the immediate vicinity of the discharge.”
As for color and turbidity, effluent monitoring (perhaps documented by photos) to determine what is “normal” would be a prudent first step in deciding on an appropriate permit limit. There being no precedent for this, and in light of PaDEP’s stated goal (not visually objectionable or persistent), the author proffers the following narrative “limit” as a starting point for discussion: “foam to appear on no more than 10% of the water surface within the discharge plume and less than 100 feet of the discharge point; and no visible foam more than 500 feet from the point of discharge.” This formula at least puts some numbers in the permit that can be checked by using photographs (now readily taken with any cell phone). Since the standard is technology-based, each permittee will have to suggest an acceptable TBEL based on its documented performance in light of the goals stated in the Preamble.
In sum, the new regulations replace a vague narrative water quality-based standard that was difficult for PaDEP to apply with a new and even more ambiguous narrative technology-based standard that shifts the interpretive burden (and substantial compliance costs) onto the shoulders of dischargers. Over the next few years, as the over 2,000 NPDES permits in the Commonwealth are renewed under these new and different rules, the hope is that some standardized method of addressing the concerns will be developed cooperatively between PaDEP and the regulated community.
It is difficult to find fault with steps taken to move toward meeting a national goal now twenty-five years past due. Unfortunately, the manner in which PaDEP took the latest step has created a host of new risks for industrial dischargers and POTWs that may take years to resolve. The point to remember is that a large share of the burden has been shifted to the permittees, and those that do not understand and react appropriately to these changes are likely to find themselves saddled with permit requirements that simply cannot be met. Preparation, data gathering, and an open dialogue with the PaDEP permitting (and enforcement) staff before the next permit is issued will go a long way toward preventing significant adverse consequences and hopefully will reduce compliance costs somewhat.
 See section 101(a) of the Clean Water Act, 33 U.S.C. § 1251(a).
 Originally, TBELs for POTWs were to be further reduced to “best practicable treatment” by 1983; this provision (CWA § 301(b)(2)(B)) was repealed in 1981.
 Although the Act requires that EPA review all industrial ELGs every five years, no such requirement applies to secondary treatment standards. See CWA § 301(d) (33 U.S.C. § 1311(d)).
 “Concentrations of chlorophyll a in free floating microscopic aquatic plants (algae) may not exceed levels that result in ecologically undesirable consequences that would render tidal waters unsuitable for designated uses.” COMAR 26.8.02.03-3.C(10).
 Implemented more than four years before a TMDL was actually developed for the Bay, under EPA’s “fire, aim, anybody ready?” approach to the Chesapeake Bay TMDL.
 25 Pa. Code § 92.51(6) (superseded). (Section 93.6, still in effect, retains this standard while adding “odors ” to the list of regulated pollutants.)
 Technically, regulatory changes are only proposed by PaDEP; they are carried out by the Environmental Quality Board. Since PaDEP proposes and drafts the regulations, however, the Department is, for all practical purposes, the author of any regulatory changes.
 The final-form 2000 secondary treatment regulations included a reference to the standards for industrial facilities at § 95.2 (1)-(3), which set pH and oil and grease discharge standards. However, since this provision (§ 92.2c(b)(4)) was inserted in the final published rule at the last minute without notice or opportunity for comment, this section was not properly promulgated and was unenforceable. That defect was corrected by the 2010 rulemaking.
 The Proposed Rulemaking also included a number of controversial provisions that were not retained in the final rulemaking and need not be discussed here.
 PaDEP has indicated informally that the new more stringent requirements will not be imposed immediately, but will be incorporated into the next NPDES permit. While the regulations themselves do not include this assurance, it is hoped that regional enforcement staff will honor that promise.
 40 CFR § 133.105.
 40 CFR § 133.103(e) and (d), respectively; reproduced virtually ver batim at § 92a.47(g) & (h).
 Inexplicably, in the Preamble to the Final Rulemaking (41 Pa. Bul. 5773) PaDEP stated that there would be no new compliance costs associated with these standards because the revised regulations “do not include new broad-based treatment requirements that would apply to most facilities.”
 In some POTW effluents, oil and grease are apparent as small, widely dispersed floating white flecks. Both BOD and oil-and-grease testing prove that these particles are a minuscule fraction of the discharge and do not result in water quality concerns, but because they concentrate on the surface, they can appear to the inexperienced eye to constitute a significant fraction of the discharged water.
 Under § 92a.46(c) “floating materials” are prohibited, but “foam”-clearly a “floating material”-is allowed (if provided for in the permit). According to the Preamble to the Proposed Rulemaking, the prohibition on “floating materials” only applies to “floating solid materials.”