Laboratory Scale Investigations of Potential Odour Reduction Strategies in Biosolids

This study investigated sources of odours from biosolids produced from a Western Australian wastewater treatment plant and examined potential odour reduction strategies on a laboratory scale. Odour reduction methods that were trialled included chemical additions and reduction of centrifuge speed. Chemical addition trials were conducted by adding alum, polyaluminium chloride or ferric chloride to digested sludge that had been sampled prior to the dewatering stage. Trials of chemical addition (alum) to plant dewatered cake were also undertaken. The impact of reducing centrifuge speed on biosolids odour was also investigated using a laboratory scale centrifuge calibrated to operate such that the shear forces on the sample would, as closely as possible, represent those on the plant. To identify the odorous compounds present in biosolids and to assess the effectiveness of the odour reduction measures, headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry (HS SPME-GC-MS) methods were developed. Target odour compounds included volatile sulphur compounds (e.g. DMS, DMDS, DMTS) and other volatile organic compounds (toluene, thylbenzene, styrene, p-cresol, indole, skatole and geosmin). In our laboratory trials, aluminium sulphate added to digested sludge prior to dewatering offered the best odour reduction strategy among the options that were investigated, resulting in approximately 40% reduction in peak concentration of the total volatile organic sulphur compounds (TVOSC), relative to a control sample

Odour reduction strategies for biosolids produced from a Western Australian wastewater treatment plant: Results from Phase I laboratory trials

This study investigated sources of odours from biosolids produced from a Western Australian wastewater treatment plant and examined possible strategies for odour reduction, specifically chemical additions and reduction of centrifuge speed on a laboratory scale. To identify the odorous compounds and assess the effectiveness of the odour reduction measures trialled in this study, headspace solid-phase microextraction gas chromatography-mass spectrometry (HS SPME-GC-MS) methods were developed. The target odour compounds included volatile sulphur compounds (e.g. dimethyl sulphide, dimethyl disulphide and dimethyl trisulphide) and other volatile organic compounds (e.g. toluene, ethylbenzene, styrene, p-cresol, indole and skatole). In our laboratory trials, aluminium sulphate added to anaerobically digested sludge prior to dewatering offered the best odour reduction strategy amongst the options that were investigated, resulting in approximately 40% reduction in the maximum concentration of the total volatile organic sulphur compounds, relative to control

Impact of bromide and iodide during drinking water disinfection and potential treatment processes for their removal or mitigation

In this study, the impact of bromide and iodide on disinfected waters was examined and potential treatment technologies for their removal or mitigation were investigated. Distributed waters from two Western Australian drinking water sources were evaluated in terms of their bromide and iodide concentrations, disinfection by-product (DBP) formation, halogen-specific adsorbable organic halogen (AOX) formation and chlorinous odours after disinfection. In both systems, the brominated DBPs dominated the measured DBPs and, in both cases, the known DSPs accounted for only 30% of total organohalogens. Chloramination with a sufficient free chlorine contact time followed by ammonia addition, rather than preformed monochloramine, may be a viable mitigation strategy for the minimisation of I-OBPs, since exposure to free chlorine should promote the conversion of iodide to iodate, a safe form of iodine. This study has shown that bromide plays an important role in this process, mainly by enhancing the preferred conversion' of iodide to iodate. Ozone pre-treatment selectively oxidised iodide to iodate and minimised the formation of I-OB Ps. Complete conversion of iodide to iodate, while minimising the bromate formation to below the guideline value of 10 µg L-1 was achieved for a wide range of ozone concentrations in raw waters, including raw waters with high bromide concentrations

An investigation of routes towards naturally occurring naphthopyrans

Many natural products possessing the 3,4-dihydro-1H-naphtho[2,3-c ]pyran ring system occur as 5,10-quinones. Owing to their significant biological activity as antibiotics or potential antineoplastic agents, the 3,4-dihydro-lH-naphthopyran-5,10-quinones have attracted considerable interest and many have been synthesised by several research groups. However, the corresponding non-quinonoid naphthopyrans have received little attention. The investigations described in this thesis are directed towards a synthesis of glucoside B 7, the non-quinonoid cleavage product of the naturally occurring aphid pigments protoaphin-jb, protoaphin-sl and deoxyprotoaphin, as well as related naphthopyrans. In the first chapter, the isolation and identification of the aphid pigments is presented. This is followed by a brief review of previous syntheses of some compounds related to the aphid pigment derivatives, focusing on the syntheses of the pyran ring system. The racemic synthesis of the aphid pigment derivatives quinones A and A' and deoxyquinone A and previous efforts involving models for the synthesis of glucoside B are reviewed in the latter part of the chapter. The first asymmetric approach towards the quinonoid derivatives of the aphid pigments is also discussed. Several approaches for the preparation of glucoside B are described. In Chapter 2, the first approach towards a racemic synthesis of glucoside B is described through a key stereoselective isomerisation of 4-aryl-2,5-dimethyl-1,3-dioxolanes into pyrans using titanium tetrachloride, an intramolecular version of the Mukaiyama reaction. A possible approach towards the first asymmetric synthesis of glucoside B, involving an intramolecular reaction between metal phenolates and chiral aldehydes is proposed in Chapter 3. Since glucoside B lacks an oxygen in the 5-position, the possibility of cleaving this oxygen from an appropriate precursor is investigated first. A highly promising synthetic strategy is detailed in Chapter 4. It involves intramolecular cyclisation of asymmetric (3'-hydroxyphenyl)aldehydes under mildly acidic conditions. These are prepared by the initial transformations of commercially available 2,3-dihydroxybenzaldehyde into 1-(3'-benzyloxy-2'-methoxyphenyl)ethanol. The aliphatic side chain is then extended by formation of a benzylic ether with (S)-ethyl lactate. Ultimately, two diastereomeric optically pure phenols, each bearing an aldehydic side chain derived from (S)-ethyl lactate, are prepared. Thus, the first chiral synthesis of a benzopyran having the same absolute stereochemistry as the enantiomer of glucoside B, i.e., benzo[c]pyran 246, is presented

Removal of organic micropollutants in waste stabilisation ponds: A review

As climate change and water scarcity continue to be of concern, reuse of treated wastewater is an important water management strategy in many parts of the world, particularly in developing countries and remote communities. Many countries, especially in remote regional areas, use waste stabilisation ponds (WSPs) to treat domestic wastewater for a variety of end uses, including using the treated wastewater for irrigation of public spaces (e.g. parks and ovals) or for crop irrigation. Thus, it is vital that the resulting effluent meets the required quality for beneficial reuse. In this paper, both the performance of WSPs in the removal of organic micropollutants, and the mechanisms of removal, are reviewed. The performance of WSPs in the removal of organic micropollutants was found to be highly variable and influenced by many factors, such as the type and configuration of the ponds, the operational parameters of the treatment plant, the wastewater quality, environmental factors (e.g. sunlight, temperature, redox conditions and pH) and the characteristics of the pollutant. The removal of organic micropollutants from WSPs has been attributed to biodegradation, photodegradation and sorption processes, the majority of which occur in the initial treatment stages (e.g. in the anaerobic or facultative ponds). Out of the many hundreds of organic micropollutants identified in wastewater, only a limited number (40) have been studied in WSPs, with the majority of these pollutants being pharmaceuticals, personal care products and endocrine disrupting compounds. Thus, future research on the fate of organic micropollutants in WSPs should encompass a broader range of micropollutants and include emerging organic pollutants, such as illicit drugs and perfluorinated compounds. Further research is also needed on the formation and toxicity of transformation products from organic micropollutants in WSPs, since the transformation products of some organic micropollutants can be more toxic than the parent compound. Combining other wastewater treatment processes with WSPs for removal of recalcitrant organic micropollutants should also be considered

Impact of bromide on halogen incorporation into organic moieties in chlorinated drinking water treatment and distribution systems.

The impact of elevated bromide concentrations (399 to 750µg/L) on the formation of halogenated disinfection by-products (DBPs), namely trihalomethanes, haloacetic acids, haloacetonitriles, and adsorbable organic halogen (AOX), in two drinking water systems was investigated. Bromine was the main halogen incorporated into all of the DBP classes and into organic carbon, even though chlorine was present in large excess to maintain a disinfectant residual. Due to the higher reactivity of bromine compared to chlorine, brominated DBPs were rapidly formed, followed by a slower increase in chlorinated DBPs. Higher bromine substitution and incorporation factors for individual DBP classes were observed for the chlorinated water from the groundwater source (lower concentration of dissolved organic carbon (DOC)), which contained a higher concentration of bromide, than for the surface water source (higher DOC). The molar distribution of adsorbable organic bromine to chlorine (AOBr/AOCl) for AOX in the groundwater distribution system was 1.5:1 and almost 1:1 for the surface water system. The measured (regulated) DBPs only accounted for 16 to 33% of the total organic halogen, demonstrating that AOX measurements are essential to provide a full understanding of the formation of halogenated DBPs in drinking waters. In addition, the study demonstrated that a significant proportion (up to 94%) of the bromide in source waters can be converted AOBr. An evaluation of AOBr and AOCl through a second groundwater treatment plant that uses conventional treatment processes for DOC removal produced 70% of AOX as AOBr, with 69% of the initial source water bromide converted to AOBr. Exposure to organobromine compounds is suspected to result in greater adverse health consequences than their chlorinated analogues. Therefore, this study highlights the need for improved methods to selectively reduce the bromide content in source waters

Chemical removal in waste stabilisation pond systems of varying configuration

While nutrient removal has been well studied in waste stabilisation ponds (WSPs), studies of organic micropollutant removal in pond systems are limited. In this study, we investigated organic micropollutant, nitrogen and organic carbon removal in selected WSPs that differed in geographical location and pond configuration, and compared their performance to an oxidation ditch wastewater treatment plant (WWTP). Of the 232 chemicals measured, 36 were detected in wastewater influent and 33 were detected in treated wastewater effluent. New data for micropollutant removal in WSPs was generated for three pesticides or related chemicals, five pharmaceuticals, the plasticizer N-butylbenzenesulfonamide, the antioxidant 2,6-di-t-butyl-p-cresol, and two flame retardants tris(dichloropropyl)phosphate and tris(chloropropyl)phosphate isomers. Most of these micropollutants were relatively well removed in WSPs. The poorest treatment efficiency was observed in the single facultative pond system, with no maturation pond, suggesting that the presence of a maturation pond is important for chemical removal. The two WSPs in temperate climates were found to have higher concentrations of motile algae that can optimise their position with respect to light and temperature. However, to-date, the micropollutant removal by these algal species is not known. The highest removals of micropollutants in a WSP were measured in a complex WSP system with two maturation ponds, and the removals achieved were comparable to the oxidation ditch system. The key factors contributing to high micropollutant removal in this WSP were high solar irradiation and warm temperatures that promoted the growth of non-motile green algae previously found to degrade micropollutants, and photodegradation