NITRIFICATION AND ACTIVATED SLUDGE FOAMING ...

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nitrification performance. The WRF performance has become more consistent and with experience, the plant staff has become keenly aware of how quickly the system can react to changes in WAS to promote foam and scum increases. Given this sensitivity which has been seen to be more pronounced in winter operations, additional means to help reduce ammonia nitrogen pass-through during periods of higher foaming conditions were investigated. Data from the on-line ammonia analyzer monitoring secondary influent provided information that ammonia nitrogen concentrations in the influent after flow equalization varied significantly during a 24 hour period. Historically, the WRF has operated on the basis of equalized diurnal flow. This system is automated through SCADA programming for control of flow equalization basins and pumping systems. With the ammonia nitrogen concentration variability, a constant flow approach created a wide range of actual ammonia nitrogen loading to the activated sludge system. Using the SCADA system, online ammonia analyzer, and existing equalization system capabilities, an ammonia nitrogen load control system was developed. Figure 7 provides a screen shot of the nitrogen load control “switch” which is now used to target the ammonia load to the activated sludge system. Figure 7 – SCADA load control screen shot The ammonia loading control switch is located near the center of screen. As shown, the targeted ammonia loading rate is 2,600 lb/day. The switch window also includes the actual current loading value. Implementation of this control system to enable more equalized ammonia nitrogen loading provided immediate positive impact to the WRF including: • Reduced MCRT required to achieve nitrification (no need to maintain higher MCRT for the higher loading periods) • Reduced/eliminated nocardial foaming and scum – minimal Effective and Total MLSS differential • Stable aeration system demands - more consistent loading creates aeration supply consistency and lower peak power requirements; lower aeration intensity – lower foaming tendencies • Stable alkalinity demands • Stable anoxic selector operation
• Reduced scum on secondary clarifiers and improved clarifier performance • Improved final filter performance and reduced backwashing Figure 8 and 9 present SCADA screen shots of typical conditions before and after the ammonia nitrogen load control program was implemented. Figure 8 – Typical flows and load conditions prior to ammonia nitrogen load control Flow to aeration Ammonia load Chart presents the conditions of variable ammonia load with near constant flow. Ammonia loading rate range under these equalized flow conditions was 1,900 – 4,100 lb/day. Figure 9 – Typical flows and load conditions after ammonia nitrogen load control Flow to aeration Ammonia load
Page 1 and 2: NITRIFICATION AND ACTIVATED SLUDGE
Page 3 and 4: METHODOLOGY An integrated, hands-on
Page 5: DISCUSSION Nocardia sp. is a type o

NITRIFICATION AND ACTIVATED SLUDGE FOAMING ...

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