Activated Sludge

The extracellular and intracellular metabolites formed upon exposure of activated sludge microorganisms to a sublethal concentration of N-ethylmaleimide were monitored by liquid chromatography with ion trap mass spectrometry. The metabolite N-ethylsuccinimido-S-glutathione (m/z 433) was converted rapidly to N-(2-oxoethyl)-2,2-(propionylamino)propanamide (m/z 187) and N-ethylmaleamic acid (m/z 144).

Immunoblot analyses performed with three monoclonal antibodies (MAbs) that recognized the nitrite oxidoreductase (NOR) of the genus Nitrobacter were used for taxonomic investigations of nitrite oxidizers. We found that these MAbs were able to detect the nitrite-oxidizing systems (NOS) of the genera Nitrospira, Nitrococcus, and Nitrospina. The MAb designated Hyb 153-2, which recognized the alpha subunit of the NOR (alpha-NOR), was specific for species belonging to the genus Nitrobacter. In contrast, Hyb 153-3, which recognized the beta-NOR, reacted with nitrite oxidizers of the four genera. Hyb 153-1, which also recognized the beta-NOR, bound to members of the genera Nitrobacter and Nitrococcus. The molecular masses of the beta-NOR of the genus Nitrobacter and the beta subunit of the NOS (beta-NOS) of the genus Nitrococcus were identical (65 kDa). In contrast, the molecular masses of the beta-NOS of the genera Nitrospina and Nitrospira were different (48 and 46 kDa). When the genus-s...

The microbial activity within activated sludge floc is a key factor in the performance of the activated sludge process. In this study, the microenvironment of activated sludge flocs from two wastewater treatment plants (Mill Creek Wastewater Treatment Plant and Muddy Creek Wastewater Treatment Plant, with aeration tank influent CODs of 60-120 and 15-35 mg/L, respectively) were studied by using microelectrodes. Due to microbial oxygen utilization, the aerobic region in the activated sludge floc was limited to the surface layer (0.1-0.2mm) of the sludge aggregate at the Mill Creek plant. The presence of an anoxic zone inside the sludge floc under aerobic conditions was confirmed in this study. When the dissolved oxygen (DO) in the bulk liquid was higher than 4.0mg/L, the anoxic zone inside the activated sludge floc disappeared, which is helpful for biodegradation. At the Muddy Creek plant, with its lower wastewater pollutant concentrations, the redox potential and DO inside the sludge...

With membrane bioreactors, the production of surplus sludge is lower than with conventional activated sludge systems, a fact that has been confirmed in a large number of analyses. There is, however, no consensus about the dimension of the reactions and their respective causes. In order to examine these, at the University of Hanover a pilot plant with a capacity of 220 l was run for one year without any extraction of surplus sludge. The plant was started with 2 g MLSS/l; after one year, this value had risen to approximately 18 g MLSS/l. In order to be able to set the plant for different sludge loads (0.04 to 0.2 kg COD/(kg MLSS · d)), the wastewater was artificially stocked up. The emerging result was that in contrast to conventional systems the sludge growth was lower, but still continuously existing. Then, comparisons with theoretical approaches were run – among others with the ASM1-Model – which confirmed the findings. One possible reason could be the different biocoenoses, which ...

The viscosity of activated sludge plays a major role on oxygen transfer and mass transport and consequently influences the hydrodynamic regime and the system performance of a membrane bioreactor (MBR). Yield stress is an important concept in rheology related to the mixing and power requirements in a stirred tank. This study examined the rheological characteristics of activated sludge sampled in a pilot airlift MBR system for domestic wastewater treatment under ambient desert conditions, using a rotational rheometer (AR 2000, TA Instruments, USA) equipped with cone-plate geometry. Both static and dynamic yield stresses were observed at the transition point of 25 s−1 of shear rate for an MLSS concentration range of 2.74–10.2 g/L. The static yield stress is a phenomenon that has not yet been evaluated for activated sludge. The mechanisms of the co-existence of both static and dynamic yield stresses and their engineering significance are discussed. In addition, a mathematical model to describe the rheological properties of the sludge is proposed. The relationships between viscosity, MLSS, temperature and shear rate were obtained statistically. The activation energy for the viscosity of the sludge in the airlift sMBR was found to be 9.217 kJ mol−1, and could be the cause of rapid fluctuation of transmembrane pressure with temperature variations.

This work aims to evaluate the feasibility of using imidazolium ionic liquids (ILs) in the design of multiphase bioreactors for the removal of volatile organic compounds (VOCs). The IL affinity for three model VOCs (dimethyl sulfide, dimethyl disulfide and toluene) was evaluated by ...

The viability of using Moringa Oleifera seed extract as a plant based coagulant in comparison to Polyaluminium Chloride a commonly used chemical coagulant for the thickening of activated sludge was investigated. Moringa Oleifera also known as the drumstick tree or horseradish is widely found throughout Mauritius. This tree is considered as a miracle tree by many researchers due to its numerous benefits ranging from purification of water to the manufacture of oil and biodiesels. To investigate the coagulant properties of the Moringa Oleifera and Polyaluminium Chloride, the zone settling test and the jar test were conducted. The zone settling tests and the jar tests showed a difference ranging from 2.1%-4.8 % for the first 30 minutes for Moringa Oleifera and Polyaluminium Chloride which showed similar coagulant relationship. Thus Moringa oleifera was found to be as efficient as Polyaluminium chloride and can thus be easily used as a natural coagulant.

Foaming and filamentous bulking can affect some wastewater treatment plants continuously or seasonally. Here, the winter season filamentous species in KonyaWWTP were identified and associated with the operational conditions of the plant.Mainly Types 0041/0675, 021N, 0092, 1851, 0581, 0803, N. Limicola I, II, III, M.Parvicella; Zooglea, and Thiothrix II found to dominate, which represents the biodegradable industrial discharge, high θc and low F/M. In order to avoid the bulking/foaming problems, specific control measures should be preferred to non-specific ones. Low ambient temperature had not adverse affect in filamentous growth. Operational condiditons were more critical.

Wastewater effluents from the textile and other dye-stuff industries contain significant amounts of synthetic dyes that require treatment to prevent groundwater contamination. In research aimed at biotechnology for treatment of azo dyes, this study examined 288 strains of azo-dye degrading bacteria to identify efficient strains and determine incubation times required for decolorization. Initial enrichment cultures were carried out using a mixture of four structurally different dyes (Acid Red 88, Reactive Black 5, Direct Red 81, and Disperse Orange 3) as the sole source of C and N to isolate the bacteria from soil, activated sludge, and natural asphalt. Six strains were selected for further study based on their prolific growth and ability to rapidly decolorize the dyes individually or in mixtures. Treatment times required by the most efficient strain, AS96 (Shewanella putrefaciens) were as short as 4 h for complete decolorization of 100 mg l−1 of AR-88 and DR-81 dyes under static conditions, and 6 and 8 h, respectively, for complete decolorization of RB-5 and DO-3. To our knowledge, these bacterial strains are the most efficient azo-dye degrading bacteria that have been described and may have practical application for biological treatment of dye-polluted wastewater streams.

Application of gas chromatography-mass spectrometry (GC-MS) can significantly improve trace analyses of compounds in complex matrices from natural environments compared to gas chromatography only. A GC-MS/MS technique for determination of poly-β-hydroxybutyrate (PHB), a bacterial storage compound, has been developed and used for analysis of two soils stored for up to 319 d, fresh samples of sewage sludge, as well as

The removal of seven pharmaceuticals and two fragrances in the biological units of various full-scale municipal wastewater treatment plants was studied. The observed removal of pharmaceuticals was mainly due to biological transformation and varied from insignificant (<10%, carbamazepine) to>90% (ibuprofen). However, no quantitative relationship between structure and activity can be set up for the biological transformation. Overall, it can be concluded that for compounds showing a sorption coefficient (K(d)) of below 300 L kg(-1), sorption onto secondary sludge is not relevant and their transformation can consequently be assessed simply by comparing influent and effluent concentrations. The two fragrances (HHCB, AHTN) studied were mainly removed by sorption onto sludge. For the compounds studied, comparable transformation and sorption was seen for different reactor types (conventional activated sludge, membrane bioreactor and fixed bed reactor) as well as for sludge ages betwee...