GOING WITH THE FLOW

Recently, a Wall Street Journal editorial criticized the U.S.EPA policy dealing with overflows from wastewater treatment plants. ("The Obama Storm Tax", October 23, 2012, p. A16)

In wet weather conditions, some wastewater treatment facilities frequently may become burdened with excess influent water flows from tributary sewer mains. Such excess flows can arise either because the sewage collection system is a combined system--designed to receive both sanitary and storm water--or because the sanitary system is subject to inflow and infiltration in rain periods.

Under such excess flow conditions, wastewater treatment plants may be forced to bypass some of the influent to a receiving stream in order to protect the integrity of the treatment biological process for the design influent flow.

Not all bypasses, however, are due to heavy rain events. For example, the Record/Herald News (northjersey.com) reported that hurricane Sandy allegedly disabled one of the nation's largest wastewater treatment plants, forcing it to release about 300 million gallons of untreated sewage into Newark Bay. This action resulted from the wide power outage and the fact that standby generators could only power the outflow. It also was reported that other plants had to take similar action.

The Journal editorial was critical of EPA Clean Water Act enforcement measures against municipal wastewater facilities which bypass excess flows. The editorial alleged that cities are forced to enter into consent decrees with EPA to upgrade their plants, which cost local taxpayers billions of dollars. Further, such systems are subject to limits on the number of permitted bypasses. The editorial complained that such upgrades actually may not be cost effective.

The editorial may have overlooked some factors involved with bypasses. First, EPA can be both the hand that feeds as well as the hand that slaps. While enforcement actions may impose upgrade costs on utilities, EPA also spends untold millions of dollars in grants and low interest loans to cities and states for upgrades of infrastructure. This money comes from taxpayers nationwide, who in effect subsidize upgrades for the beneficiaries.

Second, not all bypasses necessarily are harmful to a receiving waterbody. Traditionally, a bypassed flow may be required to receive at least primary treatment-upwards of 85%- and chlorination. One would expect EPA to consider this to be an appropriate mitigation factor given the benefit of saving the overall treatment plant function.

Third, perhaps the real issue with the excess flow issue is not plant capacity but the cause of the excess flows in the first place. If the collection system is a combined system , them maybe a more cost-effective solution is to separate the sanitary from the storm systems, at least partially. If a collection system is sanitary only, the issue may become inflow and infiltration. Inflow results from illegal connections of downspouts, sump pumps, footing drains and the like to the sanitary system and from leaking manhole covers. Infiltration can result from broken mains and manholes. Reducing excess flows from inflow and infiltration not only can reduce the necessity for treatment plant bypasses, but also may reduce sewer surcharges and resulting backups into homes.

ILLEGAL STORM WATER CONNECTIONS...GOING AWAY FROM THE FLOW

A nemesis of a wastewater treatment facility is extraneous storm water flow to the plant in rain events. Almost all wastewater treatment facilities are designed to receive and treat only domestic sanitary sewage and pretreated industrial wastewater. Most treatment plants depend upon biological processes to treat wastewater to meet strict Clean Water Act standards upon discharge to a waterbody. If a rain event causes storm water to enter the sanitary sewer mains and to flow to the treatment plant, these biological processes can be disrupted. Wastewater can be "washed out" of the plant without having received full treatment, causing pollution of the receiving stream or lake and violation of applicable standards. In addition high storm water flows can cause sanitary sewer mains to become surcharged, resulting in backups into basements and overflows from manholes.

Extraneous storm water flows are caused by inflow and infiltration of storm water into the sanitary sewer collection system. Inflow and infiltration commonly are referred to as "I & I".

Infiltration of storm water can occur when sanitary sewer mains have become broken or separated in some manner so as to permit ground water to enter. Breaks can occur due to such diverse causes as tree roots or heaving of the soil during freeze and thaw cycles. Infiltration generally is the responsibility of the utility. However, infiltration likely is not the primary source of extraneous flows to the treatment facility.

Storm water inflows into the sanitary mains occur, for the most part, due to deliberate connection of devices which discharge storm water flow into the sanitary system. In addition, sanitary sewer manhole covers located in streets or swales can permit inflow if not sealed.

Examples of inflow devices connected to the sanitary sewer service line on customer property typically include downspouts, sump pumps which drain footing drains and window wells, patio drains, driveway drains, garage floor drains and crawl space drains. Connections which permit the inflow of storm water into the sanitary sewer system generally are deemed "illegal connections", and should be disconnected. Obviously, it can be difficult for a utility to police for illegal connections. For example, sump pumps can be disconnected and reconnected fairly easily.

Several years ago, I developed a protocol for a utility client to control illegal connections. The protocol requires customers to permit inspection of their premises to determine if there is compliance with rules prohibiting the establishment or maintenance of illegal connections. In the event of a finding of non-compliance and failure to disconnect illegal connections, or in the event or refusal to permit inspection, the utility may disconnect water or wastewater service to the customer. This protocol has been successful for the client and has been adopted by other utilities.