Two Decades of Experience with the Granular Sludge-Based ANAMMOX® Process Treating Municipal and Industrial Effluents

This paper is a review of 20 years of full-scale experience with the granular sludge-based ANAMMOX process. The ANAMMOX process is a biological deammonification process for energy-efficient removal of ammoniacal nitrogen, which has been successfully applied on dewatering reject liquors from biosolids sludge digesters (e.g., mesophilic anaerobic digestions, codigestion, thermal sludge hydrolysis process (THP)) and nutrient-rich anaerobically treated industrial effluents (e.g., fermentation industry, food industry). The ANAMMOX process is a continuously operated biological process using granular biomass. The highly active concentrated granular biomass allows for compact reactor systems and a fast start-up. Long term operations of various case studies show stable process performance of full-scale reactors treating municipal and industrial effluents, achieving ammoniacal nitrogen (NH4-N) removal in excess of 90% at low and high loading rates up to 2.5 kgNH4-N/(m3·d). Some special aspects (e.g., micro-nutrients, inhibition, alkalinity consumption) of treating various wastewaters are discussed in detail. The ANAMMOX process is demonstrated to be resilient in handling process upsets and off-spec wastewater composition.

New Advances in Aerobic Granular Sludge Technology Using Continuous Flow Reactors: Engineering and Microbiological Aspects

Aerobic granular sludge (AGS) comprises an aggregation of microbial cells in a tridimensional matrix, which is able to remove carbon, nitrogen and phosphorous as well as other pollutants in a single bioreactor under the same operational conditions. During the past decades, the feasibility of implementing AGS in wastewater treatment plants (WWTPs) for treating sewage using fundamentally sequential batch reactors (SBRs) has been studied. However, granular sludge technology using SBRs has several disadvantages. For instance, it can present certain drawbacks for the treatment of high flow rates; furthermore, the quantity of retained biomass is limited by volume exchange. Therefore, the development of continuous flow reactors (CFRs) has come to be regarded as a more competitive option. This is why numerous investigations have been undertaken in recent years in search of different designs of CFR systems that would enable the effective treatment of urban and industrial wastewater, keeping the stability of granular biomass. However, despite these efforts, satisfactory results have yet to be achieved. Consequently, it remains necessary to carry out new technical approaches that would provide more effective and efficient AGS-CFR systems. In particular, it is imperative to develop continuous flow granular systems that can both retain granular biomass and efficiently treat wastewater, obviously with low construction, maintenance and exploitation cost. In this review, we collect the most recent information on different technological approaches aimed at establishing AGS-CFR systems, making possible their upscaling to real plant conditions. We discuss the advantages and disadvantages of these proposals and suggest future trends in the application of aerobic granular systems. Accordingly, we analyze the most significant technical and biological implications of this innovative technology.

Friction and Shear Properties of Pine Biomass and Pellets

Knowledge on the mechanical properties of granular biomass is important for the design and efficient operation of equipment used for handling, storage, and processing. Their mechanical properties are used as a measure of material quality. In this study, the mechanical properties of granular biomass obtained from pines (sawdust, shavings, long shavings, and pellets) were determined under a moisture content range of 10–50%. The coefficient of sliding friction µ of four construction materials was determined using a 210-mm-diameter direct shear tester (Jenike’s shear box). To measure the shear resistance of the biomass materials (represented as torque T), a prototype vane tester was constructed. The characteristics of shear resistance with respect to time T(t) were determined for material samples under normal pressure p ranging from 5 to 30 kPa and a vane rotation rate of 3 rpm. Measurements were performed for five geometries of the rotor, reflecting typical deformation conditions encountered in the processing of granular biomass. The coefficient of sliding friction was found to be affected by the type of material, moisture content, and normal compressive pressure. Depending on the biomass material, the highest µ, which ranged from 0.50 to 0.62, was obtained for black steel, whereas the lowest µ, which ranged from 0.27 to 0.52, was obtained for aluminum. The lowest coefficient of sliding friction was observed for dry materials and high normal pressure. The torque T was observed to be affected by the rotor shape, material, normal pressure, and moisture content. The parameters presented provide information useful for the design of transport equipment and processing of granular wood biomass.

Substrate inhibition and pH effect on denitritation with granular biomass

Undissociated HNO2 (up to 2 mg dm−3) was confirmed as substrate inhibitor for granular biomass from a denitritation upflow sludge bed reactor used for biological removal of nitrite. On the contrary, total nitrite nitrogen (N-NO2 up to 500 mg dm−3) and methanol (COD up to 2000 mg dm−3) were not proven to be inhibitors. pH also affected the denitritation efficiency (optimal pH was 5.9). Reduction of HNO2 concentration in the reactor by effluent recycling is recommended.

Analysis and Modeling of the Hydraulic Behavior of EGSB Reactors with Presence and Absence of Granular Biomass at Different Hydraulic Retention Times

The efficiency of biological wastewater treatment systems is linked fundamentally to the hydraulic performance of each treatment unit. These units should guarantee an adequate contact between the microorganisms and the residual water, and the compliance with the hydraulic retention time established, in order to decrease the number of dead zones or short circuits that may exist inside the reactors. In this work, hydraulic performance was evaluated in seven Expanded Granular Sludge Bed (EGSB) reactors with a useful volume of 3,4 L and constructed in acrylic. The analysis was carried out through the stimulus-response test, using bromide as tracer. Two hydraulic retention times (8 and 24 h) and the effect of the presence of granular biomass were considered. Results were analyzed qualitatively through the construction of curves C, E and F, and quantitatively through the construction of a mathematical model of axial dispersion. The results of the hydraulic performance of the reactors revealed a marked tendency to a complete mix flow pattern, with a low effect of HRT or the presence of granular biomass on their operation.