De doelstelling van het CENIRELTA project was aan te tonen dat Anammox in de hoofdstroom van een rwzi een effectieve, robuuste, kosten-efficiënte en duurzame technologie biedt voor de verwijdering van stikstof uit huishoudelijk afvalwater. De effectiviteit en robuustheid van het hoofdstroom Anammox proces zijn beproefd op rwzi Dokhaven in Rotterdam. In hoofdstuk 2 wordt ingegaan op het materiaal en de methode op basis waarvan dit project is uitgevoerd. Daarna volgt een hoofdstuk met resultaten van de full scale A-trap op Dokhaven en sliblijn op slibverwerkingsbedrijf Sluisjesdijk. Hoofdstuk 4 focust uitsluitend op de resultaten van de demonstratie-installatie die gedurende 3,5 jaar operationeel is geweest op rwzi Dokhaven. In dit hoofdstuk komen ook de belangrijkste conclusies en aanbevelingen terug van dit specifieke onderdeel van het CENIRELTA project. In hoofdstuk 5 staan de resultaten van de economische analyse van het CENIRELTA concept voor een groene weide situatie. In hoofdstuk 6 komt kort de inpassing van de hoofdstroom Anammox op rwzi Dokhaven aan bod, met oog voor technologische en technische aspecten. Tot slot wordt er stilgestaan bij de hoofdconclusies en aanbevelingen van het CENIRELTA project.@en

Highly-loaded aerobic chemical oxygen demand (COD) removal reactors (also known as A-stage) include two main processes, COD removal by heterotrophic biomass and adsorption of COD on the activated sludge. A simple model to describe highly-loaded aerobic COD removal reactors has been developed. A one-year-set of measured data from a full scale wastewater treatment plant has been used to calibrate the efficiency of the adsorption and to evaluate the ability of the mathematical model to describe the measured data in both steady state and dynamic conditions. The approach lumped the efficiency of the settler and the adsorption with a simple but powerful approach which includes the use of the measured sludge retention time (SRT) and the settling efficiency. The effects of dynamics in terms of (i) seasonality (for water temperature, flow rate and concentration of pollutants), and (ii) daily variations in flow rate were investigated. Results showed how during winter the low water temperatures negatively impacted the efficiency of the A-stage, producing a higher COD concentration in the effluent, which eventually could impact the performance of the nitrogen removal in the B-stage. General guidelines for the application of the model to similar highly loaded A-stage reactor systems were provided.

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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.

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