Efficacy of relaxation, backflushing, chemical cleaning and clogging removal for an immersed hollow fibre membrane bioreactor.

A pilot-scale hollow fibre immersed MBR, challenged with real municipal wastewater, was studied and operated under conditions identical to those prevailing at full-scale to assess the relative influence of backflushing, relaxation, chemical enhanced backflushing (CEB) and declogging on permeability decline and recovery. The influence of relaxation and backflushing was initially assessed using the conventional flux step method; results indicated reversible fouling to be similar for each method, whilst the irreversible fouling rate was significantly reduced by backflushing. For a given total backflush volume, fouling mitigation was found to be marginally better through employing higher backflush fluxes than longer backflush durations.

Comparison of coagulation performance and floc properties using a novel zirconium coagulant against traditional ferric and alum coagulants.

Coagulation in drinking water treatment has relied upon iron (Fe) and aluminium (Al) salts throughout the last century to provide the bulk removal of contaminants from source waters containing natural organic matter (NOM). However, there is now a need for improved treatment of these waters as their quality deteriorates and water quality standards become more difficult to achieve. Alternative coagulant chemicals offer a simple and inexpensive way of doing this.

Recovery of methane from anaerobic process effluent using poly-di-methyl-siloxane membrane contactors.

This paper demonstrates the potential for recovering dissolved methane from low temperature anaerobic processes treating domestic wastewater. In the absence of methane recovery, ca. 45% of the produced methane is released as a fugitive emission which results in a net carbon footprint of -0.

The effectiveness of anaerobic digestion in removing estrogens and nonylphenol ethoxylates.

The fate and behaviour of two groups of endocrine disrupting chemicals, steroid estrogens and nonylphenol ethoxylates, have been evaluated during the anaerobic digestion of primary and mixed sewage sludge under mesophilic and thermophilic conditions. Digestion occurred over six retention times, in laboratory scale reactors, treating sludges collected from a sewage treatment works in the United Kingdom. It has been established that sludge concentrations of both groups of compounds demonstrated temporal variations and that concentrations in mixed sludge were influenced by the presence of waste activated sludge as a result of transformations during aerobic treatment.

Screening optimisation for indirect potable reuse.

An automatic backflush pre-filter used for pre-treatment for secondary wastewater re-use was evaluated and optimised at two different mesh sizes over an 18 month period. The filter was initially run with a 500 microm rating mesh size, as recommended by the supplier of the downstream membrane filtration process, and then at 100 microm to investigate any change in water quality produced and associated improved membrane performance. With the 500 microm mesh in place, the filter fouling rate was low and a backflush was initiated every 3.

Precoagulation-microfiltration for wastewater reuse.

A range of coagulant chemicals and doses, up to 2 mg/L, were trialled on a microfiltration-based indirect potable reuse (IPR) pilot plant to evaluate their impact on membrane reversible and irreversible fouling. Jar tests revealed these doses to have negligible impact on organic matter removal, whilst scoping pilot trials showed them to have a positive impact on fouling rates. Initial trials carried out over a 6-h period suggested that ferric sulphate was the most promising of the coagulants tested with regards to irreversible fouling.

The effect of organic loading rate on foam initiation during mesophilic anaerobic digestion of municipal wastewater sludge.

The impact of increasing organic load on anaerobic digestion foaming was studied at both full and bench scale. Organic loadings of 1.25, 2.