چكيده به لاتين
Excess sludge production is one of the limitations of the biologically activated sludge process. Therefore, the study aims to upgrade the MBBR process to an integrated fixed film-activated sludge (IFAS) process to reduce excess sludge production. The methodology of the research was through two axes; the first is Two scenarios were followed to eliminate sludge production in the biological activated sludge process: first, modifying the moving bed biofilm reactor (MBBR) system by increasing the sludge retention time (SRT) from 5 to 15 days; and second, upgrading the MBBR process to the integrated fixed-film activated sludge (IFAS) process by applying return activated sludge (RAS) of 50, 100 and 150% with operating hydraulic retention time (HRT) of 6, 12, 14 and 20 h. The results revealed that the first scenario reduced sludge production from 750 to 150 g/day, whereas the second eliminated sludge generation. In the second scenario, operating the system as an IFAS process with complete SRT has eliminated sludge due to sludge decay and cell lysis. Part 3 of the second scenario showed that the system achieved low effluent pollutant concentrations of 3, 12, 8, and 45 mg/L for BOD, COD, TSS, and NO3, respectively. Operating at complete SRT may eliminate sludge production but also result in higher NO3 effluent concentration due to the production of NH3 from sludge decay and cell lysis. To conclude, sludge elimination in an activated sludge system is possible by carefully controlling the process and applying RAS without additional treatment. The second axis investigated sludge reduction and process optimization modeling in the MBBR system treating sewage upgraded to the IFAS process using GPS-X8 simulation. The sensitivity analysis of DO concentration, RAS, media portion, and biofilm thickness on sludge generation was simulated. The results showed that 89% sludge reduction was observed by the increment of DO concentration from 2.7 to 5 mg/L. Likewise, an increase in the RAS ratio from 50 to 200% decreased the sludge production from 1000 to 90 g/L, resulting in a 91% reduction. In addition, it was observed that sludge was highly eliminated from 910 to 400 g/L, as the media volume increased from 45 to 55%. Furthermore, a sludge reduction from 1000 to 400 g/L was achieved when the biofilm thickness increased from 1 to 5 mm, respectively. Lastly, the process was optimized with minimum sludge production of 400 g/day, and preferable system performance attributed to TSS, BOD, COD, NO3, and NH4 effluent concentrations of 14, 5, 10, 21, and 0., respectively. This concludes that sludge reduction can be achieved by operating the MBBR system as an IFAS process, and sensitivity analysis of different operational parameters is essential to measure sludge reduction. It was concluded that biological treatment is one of the best and most reliable methods from environmental, technical, and economic standpoints. In addition, the simulation has dramatically helped in knowing the influencing conditions and sensitive factors that contribute to reducing sludge, where the theoretical part is a supportive work to strengthen the results of the practical part where those interested in it can the field of sanitation, especially those who tend to reduce sludge production.
