Features

October 2011, Vol. 23, No.10

Financing through alternative delivery options 

Guaranteeing the success of energy-efficiency and process optimization projects 

Feature 3 art Matthew C. Yonkin

Utilities are feeling the pinch as rising operations costs place greater constraints on already tight operating budgets. Wastewater and drinking water treatment plants often are two of the largest consumers of electricity and can represent a significant portion of a community’s annual budget.

Typically, there are opportunities for upgrades that can yield significant savings through energy-efficiency improvements or process optimization, but many of these projects are not being implemented because of limited funding. However, energy-efficiency and process optimization projects often can be self-funding, with the realized savings paying off all or a portion of the project implementation costs. Municipalities then can reap the benefits of improved operations and reduced life-cycle costs without increasing annual expenditures or debt service. Read full article (login required)

 

Ditch the nutrients

Dissolved oxygen control proves critical in nutrient removal performance of two oxidation ditch technologies 

Feature 4 art Thor Young, John Stullken, Doug Abbott, and Ken Benner

All wastewater treatment facilities (WWTFs) in the Chesapeake Bay watershed have been or soon will be subject to strict effluent nutrient loading limits. In Maryland, WWTFs in this watershed with capacities larger than 1900 m3/d (0.5 mgd) are required to achieve new annual average effluent concentration limits of 4.0 mg/L of total nitrogen (TN) and 0.3 mg/L of total phosphorus (TP). Different communities have used a variety of technologies to meet these limits, including oxidation ditches, sequencing batch reactors, membrane bioreactors, and nitrifying activated sludge processes followed by denitrification filters.

Two new oxidation ditch systems in Maryland were designed specifically to achieve biological enhanced nutrient removal (ENR). Both systems are of similar design capacity and are operated under similar influent flows and loads and climate conditions. Read full article (login required)

 

Reaching new lows

Proven and emerging strategies merit consideration as utilities strive to achieve ultralow phosphorus limits 

Feature 5 art Christine deBarbadillo, James Barnard, Scott Levesque, and Jim Fitzpatrick

Wastewater treatment plants (WWTPs) in North America are evaluating methods to achieve ever-decreasing effluent total phosphorus (TP) limits. For moderate phosphorus limits of about 1 mg/L, facilities can use either enhanced biological phosphorus removal (EBPR) or chemical phosphorus removal with metal salts. As TP limits approach 0.5 mg/L, facilities often add filters to ensure that effluent solids concentrations are low enough to meet the TP limit. To meet limits less than approximately 0.1 mg/L TP, facilities typically incorporate additional treatment steps such as tertiary chemical clarification prior to filtration, in which effective solids separation is critical.

As more WWTPs are required to meet ultralow TP limits (0.05 mg/L and lower), the industry is improving its understanding of phosphorus removal mechanisms and speciation. Read full article (login required)

 

Operations Forum Features

Bottling up the overflows

High-flow management program optimizes wet weather operations to reduce CSOs 

Feature 1 art Mark Young, Michael Stuer, Tom Schwartz, and James S. Drake

After years of effort, the Lowell Regional Wastewater Utility (LRWWU; Lowell, Mass.) has significantly reduced combined sewer overflows (CSOs) from its 360-km (225-mi) combined sewer system (CSS).

In 2004, LRWWU launched an initiative to gain better control of its CSO regulators to reduce untreated CSO discharges. The initial goal was to obtain remote operation of the flow and diversion control gates in the CSS to remedy manual and inefficient operation of the nine CSO diversion stations. As LRWWU became more familiar with remote control technology, automated control of its flow and diversion control gates became the objective. Read full article (login required)

 

Shedding light on an alternative

Ultraviolet disinfection of stormwater overflows and low transmittance wastewaters 

Feature 2 art Jennifer Muller, Wayne Lem, and Brian Petri

Ultraviolet (UV) light is a proven alternative disinfectant that can be used to treat combined sewer overflows.

UV has an advantage compared to chemical disinfectants because there are no health and safety concerns related to chemical storage and handling; it does not lead to environmentally harmful disinfection byproducts; and UV does not require the additional complexity and cost of subsequent chemical removal or treatment technologies. Read full article (login required) 
 

 

Considering an alternative

BNR plants share lessons learned and unexpected observations made during full-scale supplemental carbon pilot tests 

Feature 6 art Katya Bilyk, Theresa Bruton, Joe Rohrbacher, Ron Latimer, Paul Pitt, Robert Dodson, and John Dodson

Wastewater treatment plants (WWTPs) that discharge into nutrient-sensitive watersheds face strict new regulations requiring enhanced removal of total nitrogen (TN) and total phosphorus, often with levels of TN at or below 3 mg/L.

To provide sufficient denitrification to reduce to these levels, many of these facilities will require the addition of supplemental carbon to the second anoxic zones of their biological nutrient removal tanks and denitrification filters.

Methanol historically has been used for denitrification at WWTPs but for various reasons, many utilities are considering alternative carbon sources. Two mid-Atlantic municipal WWTPs conducted full-scale evaluations of supplemental carbon alternatives to evaluate whether these products were effective in meeting their low-effluent nitrogen discharge limits. Read full article (login required) 

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