Excess biological phosphorus removal in the activated sludge process using primary sludge fermentation

Abstract

This paper examines the role of short-chain volatilc fatty acids In the cxcess biological phosphorus rcmoval mechanism of the activated sludge process. The effectiveness of various substrate additions in inducing phosphorus removal was investigated through a series of laboratory and pilot-scalc experiments. Phosphorus releasc and substratc uptake both take placc in the anaerobic zone of the process and thcre appears to bc an exchange phenomenon that occurs bctwccn the two molecules. The system phosphorus removal of the process is ~mprovcd by the addition of sodium acetate to the anaerobic zone. Lt is important that the zone receives no incoming nitrate, as the added substratc will be oxidizcd in the denitrification reaction, rendering it unavailable for the phosphorus removal mechanism. Acetate and propionatc, the two substrates that are most cffcctive in inducing anaerobic phosphorus release, can be generated on-site at a treatment plant by primary sludge fcrmcntation in concentrations sufficient to significantly cnhancc the phosphorus removal characteristics of thc process.Key words: biological phosphorus removal, short-chain volatilc fatty acids, phosphorus rclcase, substrate utilization, primary sludge fermentation.Cette publication examine le r81e des acides gras volatils de chaine court dans Ic mecanisme dc ddphosphoration biologique des eaux usCes par boues activCes. L'efficacitC de divers substrats a stimuler le retrait du phosphorc en solution fut etudie i travers une strie d'cxpCriences aux Cchelles laboratoire et pilote. La liberation du phosphore dc meme quc I'absorption de substrats se situent dans la zone anaerobic du procddd ct il scmblcrait qu'un phenomenc d'Cchange s'cffectuc entrc les deux molCcules. L'efficacitC de dephosphoration biologique a ttt accru par I'ajout d'acdtatc dc sodium la zone ;~natrobie. I1 cst important que cette zone reqoive le minimum de nitrates puisqu'alors Ics substrats presents seraient utilists pour la dCnitrification plutBt que pour la dtphosphoration. Les deux substrats qui se sont rdvdlds Ctre les plus efficaces ii stimuler la libtration anaCrobie du phosphore sont I'acCtate et le propionate qui peuvcnt tous dcux etre produits par fermentation des boues primaires i I'usinc de traitement en concentration suffisante pour augmcnter de faqon significative la capacitC de dCphosphoration biologique par boues activees.Mots cle's: dCphosphoration biologique, acides gras volatils de chaine court, liberation de phosphore, consommation de substrats, fermentation dc boues primaires.Can. J. Civ. Eng. 13. 345-351 (1986)

Comparative study of biological nutrient removal (BNR) processes with sedimentation and membrane‐based separation

“…For example, the addition of readily biodegradable carbon through fermentation processes (Rabinowitz and Oldham, 1986) may be necessary to eliminate the extra P that results from the reduced observed sludge yield. Moreover, to improve nitrogen removal activity in a MEBPR system, a post-denitrification zone can be added downstream of the separation tank or, alternatively, immediately upstream as recently proposed by Vocks et al (2005).…”

Development of biological nutrient removal technology in western Canada

“…Researchers at the University of Cape Town (Rabinowitz and Marais 1980;Siebritz et al 1980) and at the City of Johannesburg (Pitman 1992) proposed modifications to the Bardenpho Process that ensured that no nitrate entered the anaerobic zone. These processes became known as the UCT Process, Modified UCT Process (see Fig.…”

“…The importance of primary sludge fermentation to the success of the BNR process was investigated at the pilot-scale by researchers at The University of British Columbia (Rabinowitz and Oldham 1985) and showed that optimized side-stream fermentation can go a long way to guarantee excellent system phosphorus removal under a variety of main process loading conditions. At the same time as the University-based research was proceeding, significant optimization studies were proceeding at the two larger Okanagan Valley BNR plants.…”

Consideraciones de diseño para la eliminación biológica de fósforo empleando procesos biopelícula

“…Una vez que aparecen los ácidos grasos fruto de la fermentación anaerobia, los BAF comenzaran el proceso de liberación de fósforo y de almacenamiento de los AGV en forma de poli-ß-hidroxi-butirato (PHB). Con el fin de evitar pérdidas de tiempo de operación, reducir del volumen de los reactores, y aumentar los rendimientos de eliminación de fósforo, diversos investigadores proponen el uso de prefermentadores de agua residual, para entregar al comienzo de la fase anaerobia la cantidad suficiente de materia orgánica en forma de AGV, de forma que el proceso de EBF no se interrumpa (Skalsky y Daigger, 1995;Eastman y Ferguson, 1981;Barnard, 1984;Rabinowitz y Oldham, 1986). Los prefermentadores empleado en los sistemas de eliminación biológica de fósforo (EBF), se basan generalmente en sistemas de acidificación a partir de fangos primarios y/o secundarios de agua residual urbana (ARU).…”