August 2010, Vol. 22, No.8

Approaching the Limit

Membrane bioreactor design for high-level phosphorus removal

Feature 1 Bruce R. Johnson, Glen T. Daigger, and David Moss

The new Spokane County (Wash.) Regional Water Reclamation Facility is designed to achieve one of the most stringent effluent phosphorus limits in North America, 50 μg/L total phosphorus (TP) on a seasonal average basis. The plant also has a 10-mg/L total nitrogen (TN) limit and a 0.25-mg/L ammonia limit. The facility uses chemically enhanced primary treatment followed by a step-feed membrane bioreactor system, with metal salts for phosphorus removal. Using metal salts essentially eliminates the recycle of phosphorus from the solids handling system, since the salts still have capacity to absorb the released phosphorus from the digestion system. Read more

Achieving these nutrient removal goals cost effectively required taking an integrated approach to facility design. In performing the design analysis, the project team evaluated the impacts of upstream chemically enhanced primary treatment

(CEPT) on biological phosphorus and nitrogen removal, the impacts of chemical phosphorus removal on biological nitrogen removal, and the impacts of dewatering system design upon secondary nutrient removal. Read full article (login required)


Making the Case for Reuse

California wine country project shows triple-bottom-line analysis can pay off

Feature 2 Kaumudi Atapattu, Tracy Clinton, and Kevin Booker

California is a world leader in water reuse, but use of recycled water in the state’s $15 billion wine industry is limited due to concerns about water quality and public perception. However, given the recent threat to water supply and potential effects of climate change, wine growers are beginning to consider alternative sources of irrigation water. As part of this initiative, the Sonoma Valley County Sanitation District (SVCSD) — in conjunction with the Sonoma County Water Agency, Valley of the Moon Water District, and City of Sonoma — initiated financial and economic analyses of recycled water use for the SVCSD Recycled Water Project. Read full article (login required) 


Operations Forum Features

Two-Stage Media Filtration Meeting 21st Century Requirements 

A conventional technology provides a progressive solution

Feature 3 Paul A. LaFiandra

Before drinking water reaches the taps of the 9 million consumers in New York City, it literally travels hundreds of miles through wetlands, streams, reservoirs, and aqueducts in the upstate watershed regions and then through the city’s massive water distribution network. Although many obstacles exist to keeping the water of an unfiltered water supply system protected, none is more obvious than the need to ensure that discharges from upstream wastewater treatment plants (WWTPs) in the watershed are of the highest quality. For a number of these WWTPs, the conventional technology of sand filtration with a new “dynamic” has made all the difference in the world. Read full article (login required)


Shifting the Paradigm

Anaerobic digestion and combined heat and power for small treatment plants 

Feature 4 Eian Lynch and William Fitzgerald

Many wastewater treatment facilities face the challenges of high energy costs and limited options for biosolids use and disposal. While anaerobic digestion integrated with a combined heat and power (CHP) system can be one of the most effective methods to overcome these challenges, such methods have traditionally not been cost-effective for smaller facilities — smaller than 10 mgd (38,000 m3/d). But a recent study has shown that anaerobic digestion with CHP using industrial and farm-type digester tanks and codigestion of municipal solids with highly degradable organic feedstocks can be technically feasible and economically beneficial for small to medium-size wastewater treatment facilities (WWTFs) with no digestion infrastructure. Read full article (login required)


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