Anaerobic monodigestion of poultry manure: determination of operational parameters for CSTR

In this work the anaerobic monodigestion for the treatment of turkey manure was evaluated, without its codigestion with another substrate. The effect of the organic loading rate (OLR) and the substrate concentration (high total solids (TS) concentration) or product concentration (high volatile fatty acids (VFA) and/or ammonia (NH(3)-N) concentrations) was studied. The results show that for a continuous stirred tank reactor (CSTR) operation, a maximum of 40 g/L of TS and 4.0 g/L of ammonium (NH(4)(+)) was required. In addition, the maximum organic loading rate (OLR) will not exceed 1.5 kg VS/m(3)d. Higher TS and NH(4)(+) concentrations and OLR lead to a reduction on the methane productivity and volatile solids (VS) removal. During the CSTR operation, a high alkalinity concentration (above 10 g/L CaCO(3)) was found; this situation allowed maintaining a constant and appropriate pH (close to 7.8), despite the VFA accumulation. In this sense, the alkalinity ratio (α) is a more appropriate control and monitoring parameter of the reactor operation compared to pH. Additionally, with this parameter a VS removal of 80% with a methane productivity of 0.50 m(3)(CH4)/m(3)(R)d is achieved.     

The laminar/turbulent transition in a sludge pipeline

Globally, wastewater treatment plants are under pressure to handle high concentration sludge in a sludge treatment line. Unawareness of the non-Newtonian behaviour of the thickened sludge has the potential to cause unexpected problems when the fluid behaviour changes from turbulent to laminar flow. In this study, sludge apparent viscosity was plotted as a function of total suspended solids concentration (TSS) and shear rate. Then, the transition velocity based on several predictive models in the literature was determined. This analysis provides a practical basis for the prediction of the pipe flow behaviour of thickened sludge in troubleshooting and engineering design.     

Ammonia oxidizing bacterial community composition and process performance in wastewater treatment plants under low temperature conditions

Nitrification can be difficult to maintain at wastewater treatment plants (WWTPs) during cold periods resulting in disrupted nitrogen removal. The aim of this study was to relate nitrification process performance to abundance and composition of the ammonia oxidizer communities in two closely located municipal WWTPs in Sweden during an eight month period covering seasonal changes and low temperature conditions. Both facilities showed lower NH(4)(+)-N removal efficiency and nitrification rates as temperature decreased. However, one of the plants had a more stable nitrification rate and higher ammonia removal efficiency throughout the entire period. The differences in performance was related to a shift in the composition of the bacterial ammonia oxidizing community from a Nitrosomonas oligotropha-dominated community to a mixed community including also Nitrosomonas ureae-like ammonia oxidizers. This was likely a response to differences in NH(4)(+)-N and organic loading.     

Microaerophilic conditions support elevated mixed culture polyhydroxyalkanoate (PHA) yields, but result in decreased PHA production rates

For commercial polyhydroxyalkanoate (PHA) production the objective is to maximise the fraction of feedstock that ends up as polymer, and minimise biomass growth. In this paper, oxygen limitation was applied to achieve this. Intracellular PHA content in mixed cultures in batch systems operated with low and high DO was compared. It is shown that in microaerophilic conditions a higher fraction of substrate is accumulated as PHA in comparison to high DO conditions, evidenced by elevated intracellular PHA content: in the order of 50% higher in the early stages of accumulation. However, the accumulation capacity is not affected by DO. The PHA content in biomass in both the low and high DO systems reached approximately 35%. The time taken for the PHA content in the low DO system to reach capacity was three times longer than in the high DO system.     

Rab7 and actin cytoskeleton participate during mobilization of β1EHFNR in fibronectin-stimulated Entamoeba histolyticatrophozoites

In vitro interaction of Entamoeba histolytica trophozoites with fibronectin (FN) induces redistribution of the amoebic fibronectin receptor (β1EhFNR). Trafficking of beta1 integrins is important for cell adhesion and migration in higher eukaryotes and requires the participation of Rab proteins. In E. histolytica, the machinery involved in integrin trafficking is not completely known. EhRab7 is a 24.5-kDa protein whose alignment with other Rab7 proteins demonstrated that it shared significant homology with Rab7 proteins from other organisms, including humans. Using different types of microscopy (fluorescence and confocal microscopy), it was established that Rab7 and the actin cytoskeleton participated in the mobilization of β1EhFNR in FN-stimulated trophozoites. β1EhFNR and Rab7 co-localized only in vesicular structures at 5 min, and at longer time (1 h), both co-localized in both plasma membrane and in vesicular structures; at the same time, Rab7 co-localized with specific actin structures (phagocytic vacuoles). At 5 h the β1EhFNR, Rab7, and actin co-localized at the plasma membrane, and only β1EhFNR and Rab7 decorated vesicles of different sizes. Actin and Rab7 co-localized in a cap-like structure at one end of the cell. Fluorescence resonance energy transfer and electron microscopy confirmed the close interaction between β1EhFNR and Rab7. Moreover, the use of a lysosome-specific marker (LysoTracker) and a Golgi-specific marker (NBD C(6)-ceramide) allowed us to establish that, at some point within the endocytic route, β1EhFNR and Rab7 co-localized within a lysosome-type organelle, but not a Golgi-like organelle, which indicated that this integrin-like molecule was returned to the plasma membrane via exocytic or secretory vesicles.     

MRT letter: Human bloodstains on antique aboriginal weapons: a guiding low-vacuum SEM study of erythrocytes in experimental samples on ethnographically documented biological raw materials

The aboriginal use of reed and bone as raw materials for knives and daggers, respectively, has been well-documented ethnographically in some geographical areas of Melanesia. Because of the significant role that these weapons played in inter- and intra-ethnic aggression, they can potentially have retained smears from the contact with human blood. To carry out a guiding low-vacuum scanning electron microscopy (SEM) study of specific interest to ethnography, the outsides of a fragment of stalk of giant cane (Arundo donax) and tibial diaphysis of domestic sheep (Ovis aries) were smeared with peripheral human blood. No biological specimen preparation was applied to the samples. After just over 1 month, bloodstain boundaries and their neighboring inner areas were examined via secondary electrons by a variable-pressure SEM (VP-SEM) working in low-vacuum mode. On both substrates, bloodstains exhibited micro-scales. No janocyte (erythrocyte negative replica) was observed in the examined areas. However, erythrocytes were seen crowded together as grain-shaped corpuscles in the smear on reed, and several hecatocytes (moon-like shaped erythrocytes) were evidenced in the smear on bone. The results of this study suggest that a VP-SEM working in low-vacuum mode can be used fruitfully to detect blood remains in medium-sized reed and bone antique aboriginal artifacts. This procedure can prospectively help to ethnographic museum curators and aboriginal-art surveyors as an easy guiding test in the valuation of antique traditional weapons prior to acquisition, when the real use of a piece has been claimed by the supplier.     

Performance indicators for wastewater treatment plants

The Swedish Water & Wastewater Association has operated a web-based system, VASS, for the collection and compilation of key data from the Swedish water utilities since 2003. The VASS system will now be expanded to include data on operation of individual wastewater treatment plants (WWTP). The objective is to provide performance indicators (PIs) for performance and economy and the use of resources such as energy, chemicals and manpower. A set of PIs has been developed that also includes explanatory factors to compensate for differences in the condition of operation between plants. This paper discusses the data required for the calculation of PI but also for explanatory factors, quality checks and for plant operation context. The discussion is based on the experiences from a test round with the participation of 24 WWTP.     

A calibration protocol of a one-dimensional moving bed bioreactor (MBBR) dynamic model for nitrogen removal

This work suggests a procedure to correctly calibrate the parameters of a one-dimensional MBBR dynamic model in nitrification treatment. The study deals with the MBBR configuration with two reactors in series, one for carbon treatment and the other for nitrogen treatment. Because of the influence of the first reactor on the second one, the approach needs a specific calibration strategy. Firstly, a comparison between measured values and simulated ones obtained with default parameters has been carried out. Simulated values of filtered COD, NH(4)-N and dissolved oxygen are underestimated and nitrates are overestimated compared with observed data. Thus, nitrifying rate and oxygen transfer into the biofilm are overvalued. Secondly, a sensitivity analysis was carried out for parameters and for COD fractionation. It revealed three classes of sensitive parameters: physical, diffusional and kinetic. Then a calibration protocol of the MBBR dynamic model was proposed. It was successfully tested on data recorded at a pilot-scale plant and a calibrated set of values was obtained for four parameters: the maximum biofilm thickness, the detachment rate, the maximum autotrophic growth rate and the oxygen transfer rate.     

Replacing dichromate with hydrogen peroxide in the chemical oxygen demand (COD) test

The widely used standard method for chemical oxygen demand (COD) involves hazardous chromium species, and its two-hour heating protocol entails a substantial amount of energy expenditure. In the present work we report a proof of concept for a major modification of this method in the range 10-800 mgCOD/L, whereby H2O2 is proposed as a replacement oxidizer. This modification not only reduces the use of unsafe chromium species but also allows for the use of milder conditions that decrease the total energy outlay. The results are comparable with those obtained either with the standard method or with a commercial Hach? kit.