Alternative microbial technologies for micropollutant removal from secondary wastewater effluent

Trace organic pollutants, also called micropollutants, are endangering the quality of our drinking water resources. Pharmaceuticals such as painkillers, antibiotics and contraceptives, biocides such as insect repellants or anti-septic agents in toothpaste are just a few examples of the thousands of different substances used in medicine and personal care. Thanks to the advances in analytical technology, it is possible to detect and measure nanogram-per-liter quantities of these organic pollutants. This makes it possible to study their occurrence, effect and mitigation. In the search of mitigation technologies to remove these micropollutants before discharge into the environment, two techniques were investigated in this doctoral thesis. The first technique is an existing wastewater treatment process, nitrification, applied in an unconventional way to remove endocrine disrupting compounds. The second technique is a novel process using biogenic manganese oxides (BioMnOx), developed for the oxidative removal of pharmaceuticals and biocides. The concept of biogenic metals was explored further by the application of bio-palladium (Bio-Pd) for the dehalogenation of iodinated contrast media used in medical imaging. It was clearly shown that nitrifiers, more specifically ammonia-oxidizing bacteria (AOB) are able to biologically degrade 17α-ethinylestradiol (EE2) and the process was engineered in an aerated submerged fixed bed reactor (FBR), at μg L-1 and sub-μg L-1 concentrations. An interesting outcome for further implementation of nitrification as a tertiary treatment is the robustness of the nitrifying community. The technological application of BioMnOx in a membrane bioreactor (MBR) showed the removal of more than 60% of 14 out of 29 micropollutants, detected at ng-μg L-1: diclofenac (86%), triclosan (>78%), chlorophene (>89%), naproxen (>95%), diuron (>94%), codeine (>93%), dihydrocodeine (41%), morphine (60%), mecoprop (>81%), N-acetyl-sulfamethoxazole (92%), iopromide (68%), iomeprol (63%) and iohexol (72%) and clarithromycin (75%). Bio-Pd for the catalytic dehalogenation of the iodinated X-ray contrast media (ICM) iomeprol, iopromide, iohexol and diatrizoate was successfully applied in a Bio-Pd-MBR with in situ H2-production to supply the Pd-catalyst with molecular hydrogen. The novel finding here was that in situ H2 production by anaerobic bacteria was an excellent alternative to supply the Bio-Pd catalyst with molecular hydrogen

Bioaugmentation to degrade the organic de-icers acetate and monopropylene glycol at low temperatures

Two de-icers, potassium acetate and monopropylene glycol (MPG), used widespread as a runway and wing de-icer respectively, can exert high BOD in the surrounding waters. A bioaugmentation approach to degrade these de-icer compounds in the drainage water prior to discharge has been tested. A microbial consortium originating from soil was enriched at low temperatures (4 degrees C) in order to adapt to wintertime conditions. With 0.05 g CDW/L of biocatalyst, maximum specific removal rates up to 1.46 and 3.33 g acetate/g CDWd at 4 degrees C were achieved with and without biostimulation respectively. An acetate: MPG mixture of 1:3 at a total COD concentration of 0.80 and 1.20 g/L was degraded in 12 days by 83 and 70% respectively. Bioaugmentation in the field over a period of 25 days showed a removal of 88% MPG compared to 46% in the control. These results demonstrate that bioaugmentation of airport runoff water can be successfully applied to prevent organic de-icer compounds from entering the receiving surface waters

Anaerobic and complementary treatment of domestic sewage in regions with hot climates—A review

This study presents a literature review on the treatment of domestic sewage in controlled environments having the anaerobic process and specifically the upflow anaerobic sludge blanket (UASB) concept as the core, under natural hot conditions. The UASB process application is however beset by the preponderance of suspended solids, and the paper looks at its optimization via pre- and post-treatments to curb the prevailing problems, in the light of possible discharge and re-use/recycling/resource recovery, leading to efficient environmental protection. Pre-treatment clarification could be done with ferric chloride/polyelectrolyte, so that phosphate precipitates during the process. The pre-treated liquid phase can be submitted to a high rate anaerobic process, using the simple and robust UASB technology. In a subsequent post-treatment step, ammonium can be removed by ion exchange using a zeolite column through which the wastewater percolates after leaving the anaerobic digester. The various stages can also eliminate a large fraction of the pathogens present in the raw wastewater, mainly through the pre-treatment sedimentation and the ion exchange filtration. The sludge produced in the precipitation stage can be stabilized in a conventional anaerobic digester. Integration of the different treatment steps provides a sustainable technology to treat domestic sewage under hot climate conditions