Aerobic granular sludge technology can be regarded as the future standard for industrial and municipal wastewater treatment. As a consequence, a growing number of institutes and universities focus their scientific research on this new technology. Recently, after extensive Dutch research and development effort, an aerobic granular biomass technology has become available to the market. Full scale installations for both industrial and municipal applications are already on stream, under construction or in design. The technology is distinguished by the name ‘Nereda®’ and based on the specific characteristics of aerobic granular sludge. It can be considered as the first mature aerobic granular sludge technology applied at full scale. It improves on traditional activated sludge systems by a significantly lower use of energy and chemicals, its compactness and its favorable capital and operational costs.

No abstract

Separate treatment of sludge liquor (reject water) is a promising alternative for conventional biological extension of sewage plants with sludge digestion. Treatment of this nitrogen-rich water may significantly save in cost as well as in area demand. This article evaluates pilot plant investigations of five treatment options: the biofilm airlift suspension reactor, the membrane bioreactor, the bioreactor without sludge retention, stripping of ammonia (both airstripping and streamstripping) and the MAP/CAFR-process. The choice of the optimal treatment method is dependent on site-specific factors. This is demonstrated by two case studies.

Bio-augmentation can be used to obtain nitrification in activated sludge processes that operate at sub-optimal solid retention times. A side-stream process, the so-called BABE process that incorporates N-removal and augmentation of nitrifiers has been developed. The principle is to implement a nitrification reactor in the sludge return line, the so-called BABE reactor. This reactor can be fed with an internal N-rich flow (e.g. effluent from the sludge treatment). Hence the nitrification capacity of an activated sludge process can be augmented by the addition of nitrifiers cultivated in the BABE reactor. A full-scale test of the BABE technology has been at the treatment plant Garmerwolde in Groningen, the Netherlands. The set-up allowed comparing between three different lines: with the BABE reactor, without rejectwater and with untreated rejectwater. Based on this, the two important tasks (N-removal and inoculation) performed by the BABE reactor could be quantified. The results of the practical work in Garmerwolde showed a higher nitrification rate in the water line where the BABE reactor was implemented and also lower effluent ammonia. The experiments on a practical scale have demonstrated univocally the effective and stable operation of the BABE technology. In addition, sludge samples in different streams as well as from the BABE reactor were analysed with FISH technique. The FISH results illustrated the augmentation effect of the BABE reactor on the stream with the BABE reactor. A mathematical model, based on ASM1 model and implemented in AQUASIM was developed and used for simulating the treatment plant of Garmerwolde. The simulation results indicated that better effect of the BABE technology is expected at lower ambient temperatures and smaller volume of the BABE reactor. The BABE reactor could also allow for providing more space for de-nitrification in the main water line when nitrification is efficient enough.

No abstract