Modulated Rotary Distributor DriveBioDoc™ Trickling Filter

Slow Down that Trickling Filter!

The average U.S. trickling filter distributor

should be slowed daily to 5-10% of

its current rotational rate.

Cover/Salt Lake City installs the first of eight BioDoc drives on its 173 ft x 7 ft deep trickling filters.

Back in the late forties, English practitioners discovered the benefits of lengthening the dosing cycle to enhance the performance of trickling filters. Since 1987. And increasing number of U.S. plants have experienced the benefits of slowing down their trickling filters—like enhanced BOD, removal, reduced cyclic sloughing, fewerodors, happier neighbors.

But slowing the distributor is only the beginning. We’velearned a thing or two more in the past few years about enhancing the performance of trickling filters – three important things, in fact:

• a daily flushing cycle to clean the media

• an operating cycle to promote deeper bio-growth

• an operating cycle to encourage maximum wet ting during peak loads periods.

What was needed, however, was a distributor drive designed to produce the optimal variation in rotational speed and dosing rates.

WesTech in tune with the needs and leading the trend, introduced a patented design to handle the task. We call it the BioDoc rotary distributor.

*U.S. Patent Nos. 5,096,588 and 5,160,435

Effect of Dosing Frequency on Filter Efficiency

Improved BOD Perfomance - % 5

100

120

130

Minutes

Typical Operation 15-30 sec

SK Operation 2-6 min

Flushing 15:1

110

0 5 10 15 20 25

Proven & AcceptedSide-by-side tests of the BioDoc modulated drive and aconventional unit revealed that, while settled BOD5 removals were similar, the BioDoc drive kept the mediacleaner and improved oxygenation. Results showed a 15% higher BOD5 oxidation and 50% increased nitrification.

Equally attractive to the plant personel were the health and social benefits of no odors, no flies and no angry phone calls – and all at a price of less than %1 of the current cost of a trickling filter installation.

Understanding SK plays a key rolein optimizing the multi-step dosingoperation. The BioDoc controller simplifies the task at a low cost. Forone, its advanced distributor controlsystem is not off-the-shelf equipment;rather, it is programmable for the specific needs of the individual plants. Using either an average diurnal flow pattern or signals from the plant flowmeter, the BioDocdrive with a 20:1 speed adjustment range can regulate the rotational speed to achieve the optimum low and high SKs.

SK Defined SK – from the German work Spulkraft meaning “flushing intensity” – is defined as the depth(in millimeters) of water deposited in the passage of one distributor arm(SK, mm/pass of arm). Automated

Media Flushing. Solids buildup andodors in the filter are controlled byincreasing the SK values or flushingintensity through low frequency dosing. The BioDoc controller slowsthe rotational speed of the distributorto provide flushing intensity (high SK) inversely proportional to plant flow. Thus, the flushing cycle is reserved for off-peak hours when plant flow is lowest. A loss in biological performance during the flushing cycle is avoided becauseof the low filter loading and excessclarification capacity.

Daily flushing is critical to keep the media clean and the air and water passageways clear. In a short time, the BioDoc drive stabilizes the biomassinventory and optimizes the perfor-mance of the trickling filter.

Optimize Retention Time. Lower SKs come into play during peak loadings to maximize retention time and treatment capacity. Here again, the BioDoc drive regulates the dosing rate as a function of the plant influent. Using an SK optimizing algorithm based on plant flow, the BioDoc unit institues the proper rotational speed and the best daily SK profile. Modulating from a lower to a higher rotational speed (lower SK) at increasing organic loadings produces better distribution of the nutrients throughout the entire media depth. This proprietary method results in higher trickling filter capacities by promoting better biomass growth in the deeper regions of the media.

Optimizing through controlled dosing

25 0

50

100

150

200

250

300350

3.00 6.00 9.00 12.00

Time

Plant Flow (mgd)

Rotary Distributor Speed ControlCentral Valley WRF, Utah

SK Dosing Rate (mm/Pass)

15.00 18.00 21.00 24.00

30354045505560657075

Performance ResultsBioDoc drive vs. conventional drive

Settled Removal - %

05BOD 1 1 1TSS NHN

20

40

60

80

100

Conventional Drive BioDoc Drive

93.4 91.5

61.376.1

21.7

42.7

With a 24-hour operation and a constant loading cycle,industrial filters are prime candidates for the multi-stepdosing operation. Plants need to institute a flushing cycleon an average of one to size times daily. Whithout it mediafouling will impair performance. Case in point is BioKyowa,a pharmaceutical company that produces L-Lysine Monohydrochloride at its Missouri plant.

After BioKyowa shut down its roughing treatment efficiencyof 35 – 40% BOD5 removal. Higher than design loadings impacted process performance and a wastewater thatcontained an appreciable amount of slowly and non-degradable organics had created an overwhelming buildup of solids in the filter media. After five years of operation,BioKyowa had two badly fouled and odorous filters on its hands.

BioKyowa’s two center drive rotary distributors were retrofitted with BioDoc drives which slowed the distributors from the conventional operation of two revolutions per minute and 35mm/pass. Today, the roughing filters operate at a SK of 315 mm/pass and a flushing intensity of 700 pass.After size months of operation, the multi-step dosing operation had cleaned out the 24-foot deep towers. Today, a year later, the filters perform better than the initial operation in 1985 and at 264% of the design loading!

© WesTech Engineering, Inc. 2012

Represented by:

Power DownThrough some creative experimentation of its own, Ojai valley had discovered a method to flush excess solids fromthe media. Their solution was to pump excessive amounts of water into the filters solely for flushing action. The trickling filters cam clean but with a significant increase in electrical power costs. WesTech retrofitted their rotary distributors with the BioDoc peripheral drive. In a year’s time, the plant recouped the total retrofit cost in power while maintaining performance.

Unplugged