Water use vs. socio-economic factors in a water stressed urban area having economic affluence

The paper presents household water-use data collected from a water use survey in an urban area located in a water stressed region in the Middle East. The purpose of the survey was to investigate the effect and relationships of water shortage, economic effluence and socioeconomic attributes of house holds on per capita water use in the area. Results indicated wide variation of water uses in smaller districts of the urban area. In small areas socioeconomic factors are significantly related to per capita water use. However, when total urban area is considered, same set of factors do not show any meaningful relationship to per capita water use. Water use in summer is about 2-6 times more than that in winter. Over all per capita water use in the area is recorded to be one the highest in the world

Dynamic modeling of sludge compaction and consolidation processes in wastewater secondary settling tanks

The double exponential settling model is the widely accepted model for wastewater secondary settling tanks. However, this model does not estimate accurately solids concentrations in the settler underflow stream, mainly because sludge compression and consolidation processes are not considered. In activated sludge systems, accurate estimation of the solids in the underflow stream will facilitate the calibration process and can lead to correct estimates of particularly kinetic parameters related to biomass growth. Using principles of compaction and consolidation, as in soil mechanics, a dynamic model of the sludge consolidation processes taking place in the secondary settling tanks is developed and incorporated to the commonly used double exponential settling model. The modified double exponential model is calibrated and validated using data obtained from a full-scale wastewater treatment plant. Good agreement between predicted and measured data confirmed the validity of the modified mode

Sensitivity analysis of the secondary settling tank double-exponential function model

The secondary settling tank plays a very crucial role in achieving the very strict effluent standards of wastewater treatment plants. To investigate the ability of the widely used secondary settling tank model, the double-exponential model, to predict the dynamic behavior, a factorial sensitivity analysis was carried ou

Modelling the competition between sulphate reducers and methanogens in a thermophilic methanol-fed bioreactor

Sulphate can be removed from wastewater by means of biological anaerobic reduction to sulphide. The reduction requires the presence of a substrate that can serve as an electron donor. Methanol a suitable electron donor for sulphate reduction under thermophilic conditions. In an anaerobic system containing methanol and sulphate, acetogenic bacteria (AB) and methanogenic archaea (MA) compete with sulphate reducing bacteria (SRB) for methanol or its degradation intermediates. Previously obtained results indicate that at 65 degrees C SRB and MA mainly compete for the intermediate hydrogen instead of methanol. For efficient use of methanol as electron donor for sulphate reduction it is important that for the treatment of sulphate wastewater in an anaerobic reactor SRB out-compete MA. The mechanisms that determine the outcome of the competition are, however, not well understood. This paper describes a model based on growth kinetics of methanol-oxidising AB, and hydrogen-consuming SRB and MA, that can describe the competition between SRB and MA in a methanol-fed bioreactor. We present the model and its calibration using experimental data, and we discuss its shortcomings and suggest possible improvements

Forward and backward uncertainty propagation: an oxidation ditch modelling example

In the field of water technology, forward uncertainty propagation is frequently used, whereas backward uncertainty propagation is rarely used. In forward uncertainty analysis, one moves from a given (or assumed) parameter subspace towards the corresponding distribution of the output or objective function. However, in the backward uncertainty propagation, one moves in the reverse direction, from the distribution function towards the parameter subspace. Backward uncertainty propagation, which is a generalisation of parameter estimation error analysis, gives information essential for designing experimental or monitoring programmes, and for tighter bounding of parameter uncertainty intervals. The procedure of carrying out backward uncertainty propagation is illustrated in this technical note by working example for an oxidation ditch wastewater treatment plant. Results obtained have demonstrated that essential information can be achieved by carrying out backward uncertainty propagation analysi