Het doel van het DynaFil-project ‘Efficiënte vergisting met dynamische filtratie’ is het substantieel verhogen van de hoeveelheid organische stof die naar de vergisting wordt gestuurd, zodat de biogasproductie en daarmee de energie-efficiëntie van een RWZI toeneemt. Bij dit onderzoek is uitgegaan van een tweetraps ‘AB-systeem’ met dynamische filtratie, in combinatie met een anaerobe vergister met dynamisch membraan. In dit artikel is vooral gekeken hoe de A-trap kan worden geoptimaliseerd. Een korte contacttijd (15 min.), korte slibleeftijd (0,3 dagen), ijzerdosering en voldoende beluchting blijken een aanzienlijke verbetering op te leveren.@en

Current practice of wastewater treatment does not recover the full potential of energy present in wastewater. The potential of using anammox bacteria for autotrophic nitrogen removal combined with a desire for energy optimization brings new attention to the A-stage technology for organic carbon harvesting from municipal wastewater. The goal of this research was to investigate operational conditions of four full-scale A-stage processes and gain insight in the optimal conditions to harvest the maximum amount of organics present in sewage as excess sludge from the A stage. Large differences in removal efficiencies and design aspects were found between the four operational A-stage processes in the Netherlands. Biochemical oxygen demand (BOD) removal efficiencies vary between 40% and 80%, indicating that a good removal efficiency is possible, but that local conditions or design can be very influential. An optimal solid retention time (SRT) for maximal sludge production of 0.3 days was found; a longer SRT resulted in more mineralization of the chemical oxygen demand (COD). SRT control might be an important design aspect for the optimization of A-stage process. A short contact time with a minimum of 15 min and sufficient aeration were found to be optimal for soluble COD removal. Iron addition aided the removal of colloidal/suspended COD by coagulation/flocculation. Sludge flocs formed in the A-stage process are weak and sensitive to anaerobic conditions as well as shear due to, for example, pumping. Besides a good design of the A-stage itself, the further processing of the produced sludge also needs careful attention to optimize the sludge production and energy production.

@en