Biomedical subjects

B Wett

Publications and source records attributed to B Wett.

8 recordsLinked to original sources

PubMed2006

Solved upscaling problems for implementing deammonification of rejection water.

So far, extremely efficient metabolic pathways for nitrogen removal exclusively by autotrophic organisms are well established in scientific literature but not in practice. This paper presents results from the successful implementation of rejection water deammonification in a full-scale single sludge system at the WWTP Strass, Austria. Anaerobic ammonia oxidising biomass has been accumulated during a 2.5 year start-up period when the reactor size was gradually scaled up in the steps. The pH-controlled deammonification system (DEMON) has reached a design capacity of eliminating approximately 300 kg of nitrogen per day. Energy savings outperform expectations, decreasing the mean specific demand for compressed air from 109 m3(kg N)(-1) to 29 m3(kg N)(-1). Dominance of autotrophic metabolism is confirmed by organic effluent loads topping influent loads.

Ammonia↗

PubMed2006

Description of nitrogen incorporation and release in ADM1.

ADM1 represents a universally applicable biokinetic model for the mathematical description of anaerobic digestion of different types of organic substrates. Digestion of particulate composites is described as a five-stage process involving disintegration, hydrolysis, acidogenesis, acetogenesis and methanogenesis, of which the last three process steps are represented by growth kinetics of the specific degrading biomass. Decay of the produced biomass according to ADM1 is depicted by a recycle mass flux to the composite particulate substrate. Consequently two different actions are lumped into one process describing both conversion of feed substrate (depending primarily on influent characterisation) and generation of decay products (depending on digestion performance). In this presentation the introduction of a separate compound of inert decay products in analogy to ASM1 is suggested. Model calibration of separately monitored digestion of primary and secondary sludge (nitrogen content 0.030 g N/g TSS and 0.051 g N/g TSS, respectively) reveals the advantage of a clear distinction of disintegration and decay. The fate of nitrogen in the course of incorporation and release (0.016 g N/g TSS compared to 0.028 g N/g TSS) during digestion processes is comprehensible and the final ammonia concentration in the rejection water becomes predictable.

Anaerobiosis↗

PubMed2005

Parameter investigation for decentralised dewatering and solar thermic drying of sludge.

The purpose of this paper is an experimental and model assisted investigation of the capabilities of a dewatering system for sewage sludge for decentralised sites. Laboratory and field tests are performed with different initial conditions and the influences of filter medium, initial height, initial total suspended solids, temperature and relative humidity are discussed. The experimental work shows the feasibility of geotextile media for dewatering high water content sewage sludge and that the textile structure is of secondary importance. The specific filter resistance of the sludge cake is found to be the most significant factor in dewatering applications. The mathematical description of the dewatering process is based on the superposition of two models, the Conventional Filtration Theory for the filtration phase and the BT-model for the drying phase. Feasibility and limits of the theoretical approach are evaluated by means of a comparison between measurements and simulated data of cyclic reloading tests. It is found that a better filtration efficiency is achieved at higher TSS and at lower initial height of the slurry layer. Due to the viscosity decrease, a higher temperature enhances not only evaporation, but also filtration rate.

Filtration↗

PubMed2003

Impacts of separate rejection water treatment on the overall plant performance.

A separate rejection water treatment appears as a high-tech unit process which might be recommendable only for specific cases of an upgrading of an existing wastewater treatment plant. It is not the issue of this paper to consider a specific separate treatment process itself but to investigate the influence of such a process on the overall plant performance. A plant-wide model has been applied as an innovative tool to evaluate effects of the implemented sidestream strategy on the mainstream treatment. The model has been developed in the SIMBA environment and combines acknowledged mathematical descriptions of the activated sludge process (ASM1) and the anaerobic mesophilic digestion (Siegrist model). The model's calibration and validation was based on data from 5 years of operating experience of a full-scale rejection water treatment. The impact on the total N-elimination efficiency is demonstrated by detailed nitrogen mass flow schemes including the interactions between the wastewater and the sludge lane. Additionally limiting conditions due to dynamic N-return loads are displayed by the model's state variables.

Ammonia↗

PubMed2003

Carbonate addition--an effective remedy against poor activated sludge settling properties and alkalinity conditions in small wastewater treatment plants.

The impact of marble powder on the performance of small seasonal treatment plants dealing with high ammonia concentrated wastewater has been investigated. The carbonate has been added to one of two parallel lab-scale SBR-systems as an alkalinity depot and a bio-carrier. The focus of the monitoring program was put on the measurement of carbon fractions in the liquid and the solid phase and on the alkalinity conditions. Monitoring results show a significant correlation between carbonate dosage (and corresponding inorganic carbon concentration and pH-value) and sludge volume index and nitrification rate.

Ammonia↗

PubMed2002

Sludge management regulations and their applicability in mountainous regions.

The Commission of the European Communities (CEC) is just working out a new directive in order to regulate the agricultural reuse of sewage sludge. This new regulation will also effect a "special case"--sludge usage in a mountainous environment--which will be discussed in this paper. Three reuse sites at small wastewater treatment plants of mountain refuges at altitudes more than 2,000 m a.s.l. are investigated. Applied sludge, soil and drainage flow from lysimeters are analysed. Concerning heavy metal concentrations domestic sewage sludge from these sites differs significantly from municipal sludge. A comparison with background concentrations reveals that no relevant accumulative pollution of the soil is possible. An increase of coliform bacteria of maximum two orders of magnitude is preserved during the long winter period and indicates a limited hygienic risk.

Agriculture↗

PubMed2002

Mass balance of a wastewater loaded canal system: case study of Bangkok.

A dynamic water quality model was applied in order to investigate self-purification processes in highly loaded canals in the centre of Bangkok, capital city of Thailand. Oxygen production by aquatic plants induces a significant diurnal variation of the dissolved oxygen concentration. The corresponding profiles of heterotrophic growth and BOD5 concentration demonstrate the limiting impact of oxygen shortage during night time. Both self-purification mechanisms--biological degradation and settling--are considered and water-sediment interactions are calculated. Simulation results and measurement data are summarized by mass balance schemes which offer a telling characterization of the complex system.

Biodegradation, Environmental↗

PubMed2001

Feedforward aeration control of a Biocos wastewater treatment plant.

The Biocos strategy as a cyclical time controlled activated sludge system shows a great variability in operation and control. One topic such a type of treatment plant has to deal with is the optimum relation between aerobic and anoxic conditions. The aeration control has to adapt the length of the nitrification phases to the current constraints in order to save operational costs and maximise nitrogen elimination. Since wastewater treatment plants up to a certain size are usually not equipped with on-line nitrogen probes, influent flow and temperature can be taken as control parameters for the aeration system. The defined relation between influent flow and ammonia load is based on measurements and the relation between ammonia load and required aeration time is model based.

Aerobiosis↗