A Wastewater Treatment Plant has an average influent flow of 1,200,000 gallons per day. In March 2003 Advanced BioCatalytics Corporation began treating the aerobic digester with the company’s proprietary wastewater remediation product Accell®. The main objective of the trial was to investigate, if the addition of Accell® would lead to an increased %VS reduction (determined according to Arvin’s standard formula), thus increasing the sludge reduction capacity of the plant. According to the plant personnel, the operational process should achieve a 38% VS reduction at it’s minimum, with a desired range between 50-60%. Hence, a %VS reduction of 50% or more following the addition of Accell® would be considered a successful outcome of this field trial.

Accell® was added through a peristaltic pump onto the top of the WAS inside the aerobic digester. The dose was 0.75 ppm Accell® for each 1 MGD of plant influent. Duration of the study was 18 months. This extended time frame resulted in sufficient data points, to yield a statistically correct analysis despite the daily and seasonal fluctuation of the plant operation.

Table 1 summarizes the results of this study. During the 3 years (2000, 2001, 2002) prior to the addition of Accell®, the plant operated at an average of 41.8 % VS reduction, which is barely 4% above its required minimum. However, during the 18 months of Accell® treatment the plant increased its average %VS reduction capacity by more than 9% to 50.9%. That translates to approximately 22% less sludge to be processed by the plant. This is particularly interesting, because the amount of sludge entering the process increased from an average of 427,045 lb in the years 2000-2002, to 579,758 lb in 2003 and 383,989 lb in the first 6 months of 2004 (Table 2). In other words, despite an approximate 35% increase of the incoming sludge load, with the use of Accell® the plant operated for the first time within the range of its performance optimum.

Table 1: VS Reduction WWTP, CA

Before Accell® VS reduction (%)			Accell® VS reduction (%)
2000	2001	2002	2003	January-June 2004
41.5	42.8	41.0	49.1	52.7
Average:                                         41.8			50.9

Table 2: Incoming WAS WWTP, CA

Before Accell® WAS (lb)			Accell® WAS (lb)
2000	2001	2002	2003	June 2004
447,826	421,932	411,377	579,758	383,989

The addition of the biostimulant Accell® at a dose of ~0.75 ppm led to an increased reduction of %VS allowing the WWTP to operate within its range of optimum performance of 50-60% VS reduction. Comparative historical data from 3 years of operation without Accell® show clearly that the plant averaged a 41.8% VS reduction, which is very close to its performance minimum of 38%.

Furthermore, the treatment of the aerobic digester with Accell® led to a series of benefits, such as a reduction of malodor, an apparent decrease of FOG and improved drainage from the drying beds. An additional load was placed on the digester when grease, collected from grease pits, was transferred directly to the aerobic digester for removal. No negative effects on the digester operation, nor on the drainage in the drying beds was observed, clearly indicating an increased process capacity of the digester in the presence of Accell®.

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