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

Use of wastewater is increasingly gaining importance as a water supply. However, the acceptance of the final users is important for the success of such projects. The acceptability of the treated wastewater depends on the physical, chemical, and most importantly the microbiological quality of the water. Appropriately designed and operated Managed Aquifer Recharge (MAR) systems have proven to be a very effective and robust barrier against all pathogens present in wastewater. Examples of successful implementation of MAR to catalyse safe and reliable water reuse are abundant. In the Netherlands, this started with the intake river water for dune infiltration in the 1950s. These big MAR schemes still supply around one-fifth of the drinking water in the Netherlands. Research has shown that these MAR systems are crucial for disinfection of the river water and overcoming mismatches between river water availability and water demand. Cost-effective and microbiologically reliable water supply can also be attained for the agricultural sector, as shown by the Dinteloord case study. Stakeholder involvement and an integrated approach is becoming indispensable for MAR and results in increased creation of water banks, including total cost recovery based on financing from all stakeholders.@en

Sulfate-reducing bacteria (SRB) can beneficially be applied to domestic wastewater treatment. In general, formed sulfide will stay in liquid phase, resulting in an elevated sulfide content, which might have inhibiting effects on the SRB. To study effects of environmental conditions on the SRB resistance against sulfide, two sequencing batch reactors fed with artificial domestic wastewater were operated at sulfate-reducing conditions. Required sulfide concentration within the reactor was achieved by adding 400 or 800 mg COD/L (acetate and propionate), the latter resulting in proportionally more sulfide production. Batch tests revealed that sulfide inhibited the rate of sulfate reduction by 50% at a concentration of 200 mg/L sulfide for biomass from the reactor fed with 400 mg COD/L. After adaptation to a feed of 800 mg COD/L, resulting in higher sulfide exposures, sulfide was less inhibitive to SRB. Complete COD removal was achieved in the reactor fed with 800 mg COD/L, and the SRB population changed from one (Desulfotalea arctica) to two (Desulfobacter postgatei and Desulfocapsa sulfexigens) dominant species. Results indicate that SRB are capable of adapting to higher sulfide exposure. Therefore, the SRB can also be applied to treat wastewater with higher COD levels, blackwater for instance.@en

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