No abstract

The City of San Diego, California, evaluated the performance capabilities of biological aerated filters (BAFs) at the Point Loma Wastewater Treatment Plant. The City conducted a 1-year pilot-plant evaluation of BAF technology supplied by two BAF manufacturers. This paper reports on the first independent oxygen-transfer test of BAFs at full depth using the offgas method. The tests showed process-water oxygentransfer efficiencies of 1.6 to 5.8%/m (0.5 to 1.8%/ft) and 3.9 to 7.9%/m (1.2 to 2.4%/ft) for the two different pilot plants, at their nominal design conditions. Mass balances using chemical oxygen demand and dissolved organic carbon corroborated the transfer rates. Rates are higher than expected from fine-pore diffusers for similar process conditions and depths and clean-water conditions for the same column and are mostly attributed to extended bubble retention time resulting from interactions with the media and biofilm. Water Environ. Res., 80, 663 (2008).

Organic nitrogen (N org ) removal by the reverse osmosis (RO) process is not well documented in the literature. Unlike inorganic nitrogen (e.g. ammonia, nitrate, nitrite), which is consistently removed across a RO membrane as a function of process operation (e.g. flux and recovery), pH and membrane type; N org removal may vary depending on its characteristics (e.g. size, charge and hydrophobicity). The results of a pilot study that was conducted to determine the total nitrogen (TN) removal by the RO process are presented. The N org removal rates are compared with removals observed from three full-scale RO facilities and four pilot studies. The results of this analysis suggest that N org removal is variable and that RO may not consistently produce TN levels <1.0 mg/L without additional treatment. Three hypotheses to explain the variability in N org removal in the different data sets are presented.

The results of a pilot study that was conducted to determine the total nitrogen removal by the reverse osmosis process are presented. The organic nitrogen removal rates are compared with removals observed from three full-scale reverse osmosis facilities and four pilot studies. The results of this analysis suggest that organic nitrogen removal is variable and that reverse osmosis may not consistently produce total nitrogen levels less than 1.0 mg/L without additional treatment. Three hypotheses to explain the variability in organic nitrogen removal in the different data sets are presented. Water Environ. Res., 84, 588 (2012).

Pump Station 65 (PS65) is currently equipped to handle the projected 2015 peak wet-weather flow (PWWF) of 18.8 million gallons a day (MGD). However during a storm in 2004, the station's two 400HP pumps operated for a 12-hour period with a recorded peak flow of 20.2 MGD. Further, recent Public Utilities Department (PUD) projections indicate that 2015 dryweather flows will be approximately 22 MGD. Pump station capacity upgrades are required to avoid serious and costly sewage spill to the adjacent environmentally sensitive Peñasquitos Lagoon. Understanding the hydraulic capacity and physical and operating condition of the PS65 force main (FM) were critical considerations for proceeding with the needed pump station improvements. The work efforts associated with the FM assessment -the pressure gauging; hydraulic analysis; external and internal inspection; and structural condition assessment -are reviewed and the resultant City findings and actions to date are described.