Strathmore WWTP

Case Study 

The Strathmore WWTP was constructed to replace eight extended aeration lagoons. The plant was designed to process 4,000 m³/day (1 MGPD) Average Day Flow, 10,000 m³/day (2.6 MGPD) Peak Day Flow and the permit stipulated effluent of less than 20 mg/l BOD and TSS, less than 5/10 mg/l N-NH3 in summer/winter respectively, less than 1 mg/l Total Phosphorus and less than 200 MPN/100 ml fecal coliform. The plant features included headworks, two USBF bioreactors, alum storage and dosing and a UV disinfection system. Alum solution (49%) was dosed into the anoxic compartment of the bioreactors. Phosphorus precipitation and coagulation took place within the bioreactor internal circulation. Filtration was solely by the USBF sludge filters - the process did not include effluent post-filtration. The plant was operated in May 2002 by ECOfluid and turned over to the Owner’s operator in mid June 2002. Seven months of the plant operation and performance in 2002 are summarized in the following summary tables. The results confirm that loaded very close to its design capacity the plant performed well within the design parameters and better. All data are monthly averages of daily 24 hr composite samples. Daily duplicate 24 hour composite samples were sent to certified lab for analysis (Lab analysis available). Only the higher results were recorded.

OPERATING RESULTS

Bioreactor 1   Bioreactor 2   SSV MLSS SVI SSV MLSS SVI 2002 ml/l mg/l ml/g ml/l mg/l ml/g June 474 5536 85 374 5236 71 July 820 5131 162 851 5419 159 August 732 4485 167 827 4572 182 September 806 4798 171 758 4620 165 October 780 3797 206 758 3766 201 November 914 5009 185 887 4749 188 December 914 4724 194 917 5065 182 After the plant turn-over to the plant operator in mid-June the operator "experimented" with operating parameters (lower DO, reduced MLSS…). The result was much higher than typical SSV and SVI in the following months.

WASTE ACTIVATED SLUDGE YIELD

WAS WAS WAS WAS WAS Yield WAS Yield 2002 m3/m m3/m % ds kg/d kg WAS / kg BOD and TSS kg WAS / kg BOD               June 1,684 56.1 0.54 303 0.19 0.37 July 2,954 95.3 0.53 505 0.37 0.75 August 2,978 96.1 0.45 432 0.28 0.56 September 3,347 111.6 0.47 524 0.35 0.69 October 3,908 126.1 0.38 479 0.29 0.58 November 1,969 65.6 0.47 308 0.18 0.38 December 2,465 79.5 0.49 390 0.25 0.49 Average 2,758 90.0 0.48 420 0.27 0.54          Averaged over seven months and including aluminum sulphate ballast sludge Waste Activated Sludge             (WAS) yield was 0.27 kg/kg ((lb/lb) of combined BOD and TSS or 0.54 kg/kg (lb/lb) of BOD.

ALUM CONSUMPTION   Alum Alum Consumption 2002 [L/d] L/kg TP June 161 11.4 July 145 10.7 August 322 20.8 September 261 16.7 October 230 14.8 November 87 5.6 December 205 13.0 Average 201 13.3 Alum solution consumption was 13.3 litres per kg (1.6 gal/lb) of Total Phosphorus removed. This would indicate that approximately 60% of the Total Phosphorus reduction was by biological "luxury" uptake.