Nichola A. Porter

Polybrominated diphenyl ethers and polybrominated biphenyls in Australian sewage sludge

This paper presents a brief review of the international scientific literature of polybrominated diphenyl ethers (PBDEs) and polybrominated biphenyls (PBBs) in sewage sludge and a survey of these compounds in sewage sludge from 16 Australian wastewater treatment plants (WWTPs). The SigmaPBDE mean concentration in the Australian study was 1137microgkg(-1) dry weight (d.w.) (s.d. 1116) and ranged between 5 and 4 230microgkg(-1)d.w. The urban mean of 1308microgkg(-1) (s.d. 1320) and the rural mean of 911microgkg(-1) (s.d. 831) are not statistically different and are similar to levels in European sludges. Principal components analysis was performed on the data set and revealed that 76% of the data variation could be explained by two components that corresponded to overall concentration of the pentaBDE and the decaBDE commercial formulations. An analysis of variance was performed comparing PBDEs levels at three WWTPs over the years 2005 and 2006, finding differences between treatment plants (BDE-47) but no significant difference in PBDE levels in the years 2005 and 2006. Low levels of BB-153 were detected in all samples of this survey (n=16); mean 0.6microgkg(-1)d.w. (s.d. 0.5). This compound has rarely been reported in any other study of sewage sludges undertaken outside Australia. This work highlights the need for a risk assessment of PBDEs in sewage sludge when used for land application, taking into account typical levels found in Australian sludges and soils.

Investigating the distribution of polybrominated diphenyl ethers through an Australian wastewater treatment plant.

The aim of this study was to quantify the amount of polybrominated diphenyl ethers (PBDEs) released into the environment (biosolids, effluent) from a conventional Australian activated sludge treatment wastewater treatment plant (WWTP). The concentration of PBDE congeners was measured at various treatment stages and included four aqueous samples (raw, primary, secondary and tertiary effluents) and three sludges (primary, secondary and lime stabilized biosolids), collected at three sampling events over the course of the experiment (29 days). Semi-permeable membrane devices (SPMDs) were also installed for the duration of the experiment, the first time that SPMDs have been used to measure PBDEs in a WWTP. Over 99% of the PBDEs entering the WWTP were removed through the treatment processes, principally by sedimentation. The main congeners detected were BDE 47, 99 and 209, which are characteristic of the two major commercial formulations viz penta-BDE and deca-BDE. All the PBDE congeners measured were highly correlated with each other, suggesting a similar origin. In this case, the PBDEs are thought to be from domestic sources since domestic wastewater is the main contribution to the in-flow (approximately 95%). The mean concentration of SigmaPBDEs in chemically stabilized sewage sludge (biosolids) was 300microg kg(-1) dry weight. It is calculated that 2.3+/-0.3kg of PBDEs are disposed of each year with biosolids generated from the WWTP. If all Australian sewage sludge is contaminated to at least this concentration then at least 110kg of PBDEs are associated with Australian sewage sludge annually. Less than 10g are released annually into the environment via ocean outfall and field irrigation; this level of contamination is unlikely to pose risk to humans or the environment. The environmental release of treated effluent and biosolids is not considered a large source of PBDE environmental emissions compared to the quantities used annually in Australia.

A critical review of nitrogen mineralization in biosolids-amended soil, the associated fertilizer value for crop production and potential for emissions to the environment.

International controls for biosolids application to agricultural land ensure the protection of human health and the environment, that it is performed in accordance with good agricultural practice and that nitrogen (N) inputs do not exceed crop requirements. Data from the scientific literature on the total, mineral and mineralizable N contents of biosolids applied to agricultural land under a wide range of climatic and experimental conditions were collated. The mean concentrations of total N (TN) in the dry solids (DS) of different biosolids types ranged from 1.5% (air-dried lime-treated (LT) biosolids) to 7.5% (liquid mesophilic anaerobic digestion (LMAD) biosolids). The overall mean values of mineralizable N, as a proportion of the organic N content, were 47% for aerobic digestion (AeD) biosolids, 40% for thermally dried (TD) biosolids, 34% for LT biosolids, 30% for mesophilic anaerobic digestion (MAD) biosolids, and 7% for composted (Com) biosolids. Biosolids air-dried or stored for extended periods had smaller total and mineralizable N values compared to mechanically dewatered types. For example, for biosolids treated by MAD, the mean TN (% DS) and mineralizable N (% organic N) contents of air-dried materials were 3% and 20%, respectively, compared to 5% and 30% with mechanical dewatering. Thus, mineralizable N declined with the extent of biological stabilization during sewage sludge treatment; nevertheless, overall plant available N (PAN=readily available inorganic N plus mineralizable N) was broadly consistent across several major biosolids categories within climatic regions. However, mineralizable N often varied significantly between climatic regions for similar biosolids types, influencing the overall PAN. This may be partly attributed to the increased rate, and also the greater extent of soil microbial mineralization of more stable, residual organic N fractions in biosolids applied to soil in warmer climatic zones, which also raised the overall PAN, compared to cooler temperate areas. It is also probably influenced by differences in upstream wastewater treatment processes that affect the balance of primary and secondary, biological sludges in the final combined sludge output from wastewater treatment, as well as the relative effectiveness of sludge stabilization treatments at specific sites. Better characterization of biosolids used in N release and mineralization investigations is therefore necessary to improve comparison of system conditions. Furthermore, the review suggested that some international fertilizer recommendations may underestimate mineralizable N in biosolids, and the N fertilizer value. Consequently, greater inputs of supplementary mineral fertilizer N may be supplied than are required for crop production, potentially increasing the risk of fertilizer N emissions to the environment. Thus greater economic and environmental savings in mineral N fertilizer application are potentially possible than are currently realized from biosolids recycling programmes.

Investigating the levels and trends of organochlorine pesticides and polychlorinated biphenyl in sewage sludge.

A study was completed to investigate temporal trends of organochlorine pesticides (OCPs; aldrin, chlordane, dieldrin, heptachlor, hexachlorbenzene, and DDT) and polychlorinated biphenyls (PCBs) in sewage sludge. Between 2004 and 2006 the concentration of OCPs and PCBs in Australian sewage sludge (n=829) was consistently <1000mugkg(-1) dry solids DS. Dieldrin, chlordane and DDE were detected in 68%, 27% and 13% at maximum concentrations of 770, 290 and 270 microgkg(-1) DS, respectively. Time series analysis (1995-2006) of OCPs and PCBs sewage sludge concentrations (n=2266) taken from six wastewater treatment plants (WWTPs) of the same geographic region found that lindane, aldrin HCB, heptachlor, DDT, DDD and PCBs were infrequently detected (<8%). A correlation between dieldrin and chlordane levels was found (P<0.05) which provides evidence of similar environmental mechanisms facilitating movement of dieldrin and chlordane through environment compartments. It has taken more than 10years for dieldrin and chlordane to reduce to less than detectable concentrations in freshly generated sewage sludge in Australia following government restrictions. Internationally, reported sewage sludge OCP concentrations were consistently low and often less than detection limits. Therefore, OCPs are not considered to be a contaminant of regulatory concern for countries that phased out OCP use several decades ago. Concentrations of PCBs in sewage sludge were also consistently low and rarely exceeded European contaminant limits and therefore, regulatory limits may warrant review. The authors recommend that Australian authorities revise regulatory requirements for OCP and PCBs contaminant levels in sewage sludge destined for beneficial reuse as biosolids.

Application of comprehensive two-dimensional gas chromatography to the quantification of overlapping faecal sterols

Standard solutions containing a mixture of seven sterols and 5alpha-cholestane as internal standard, and sample mixtures that comprised varying ratios of sterol and stanols from green lip mussel tissue and dried cow faeces were analysed by using comprehensive two-dimensional gas chromatography (GC x GC). Quantitative results were compared with single-column GC analysis. The latter samples included sterols of interest, but which cannot be readily obtained elsewhere. It may also mimic potential environmental samples where dairy production and aquaculture (oyster, mussel cultivation) share the same catchment; environmental sterol signatures may exhibit characteristics of both sample types comprising this mixture. Whereas single-column GC-flame ionisation detection was unable to reliably quantitate target sterols, the GC x GC experiment permitted small amounts of sterols and stanols to be detected and separated. Likewise GC-MS analysis was unable to detect some of the minor sterols which coeluted on a single column. The GC x GC mode allows complete separation of several important sterols and stanols, such as 24-ethylcoprostanol, campesterol and 24-methylenecholesterol, demonstrating the enhanced resolving power of the GC x GC system. Separation of 24-ethyl-epi-coprostanol from several algal-derived interfering components was achieved, leading to higher degree of confidence in the quantitative analysis of faecal sterols. The effects of a number of operating variables--column length, carrier flow-rate and elution temperature--on component resolution and presentation of data in the two-column analysis are described.

Detection of s-triazine pesticides in natural waters by modified large-volume direct injection HPLC

There is a need for simple and inexpensive methods to quantify potentially harmful persistent pesticides often found in our water-ways and water distribution systems. This paper presents a simple, relatively inexpensive method for the detection of a group of commonly used pesticides (atrazine, simazine and hexazinone) in natural waters using large-volume direct injection high performance liquid chromatography (HPLC) utilizing a monolithic column and a single wavelength ultraviolet-visible light (UV-vis) detector. The best results for this system were obtained with a mobile phase made up of acetonitrile and water in a 30:70 ratio, a flow rate of 2.0 mL min(-1), and a detector wavelength of 230 nm. Using this method, we achieved retention times of less than three minutes, and detection limits of 5.7 microg L(-1) for atrazine, 4.7 microg L(-1) for simazine and 4.0 microg L(-1) for hexazinone. The performance of this method was validated with an inter-laboratory trial against a National Association of Testing Authorities (NATA) accredited liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) method commonly used in commercial laboratories.

Effect of centrifuge conditions on water and total dissolved phosphorus extraction from soil

Centrifugation of soils to extract soil water is widely used to investigate the chemical properties of soil water. However, no single set of standard operating conditions in terms of centrifuge time and speed have been defined. This study investigated centrifuge conditions on the effect of volume of soil water and phosphorus concentrations extracted to determine a set of standard operating conditions that could be used for soil water extraction in the future. Two contrasting soils that had been dried and rewet, a Ferrosol and a Dermosol, were used to investigate centrifuge speed (1000-3000 r.p.m.) and centrifuge time (5-30 min) on the extraction of soil water. Centrifuge speeds of 1000, 2000, and 3000 r.p.m. were trialed in this study giving relative centrifugal forces of 220, 881, and 1982g respectively. Increasing centrifuge time significantly increased (P < 0.001) the volume of soil water extracted. Almost twice as much soil water was extracted when the centrifuge time was increased from 5 to 30 min. Centrifuge speed was also a highly significant factor (P < 0.001) in increasing the volume of soil water extracted. The amount of soil water extracted increased by up to 15% when the centrifuge speed was increased from 1000 to 3000 r.p.m. The concentration of total dissolved phosphorus (TDP) did not change significantly with either centrifuge speed or time. The most important factor in determining the concentration of TDP was the soil type. The conditions that gave an adequate volume of soil water for analyses from field-moist soils in the shortest amount of time were a centrifuge force of 1982g and a time of 10 min.

An assessment of the guidelines in Victoria, Australia, for land application of biosolids based on plant-available nitrogen

In the application of biosolids to land for agricultural purposes, the supply of plant-available nitrogen (PAN) should match the crop requirements. This ensures that the crop yield is maximised while minimising the environmental risk from over-application. In Victoria, the amount to be applied is usually calculated according to the State EPA guidelines using the nitrogen limited biosolids application rates (NLBAR). These guidelines specify the mineralisation rates to be used in the NLBAR calculation for different types of biosolids. However, these rates have not been validated for Victorian soils and agricultural production systems. To test the veracity of these rates, this study quantified the amount of PAN for two different biosolids (anaerobically digested biosolids, ANDB; and aerobically digested biosolids, ADB) added to two types of soils, a sandy loam at Lara and a clay loam at the Melton Recycled Water Plant, Surbiton Park, Melton. The PAN was calculated by determining the N fertiliser equivalence of the biosolids. To achieve this, two field calibration plots were prepared, one for the biosolids and one for urea as the N fertiliser. Biosolids were applied based on total N at six rates (0, 68, 136, 204, 340 and 510 kg N ha–1); urea was applied at six rates (0, 60, 120, 180, 240 and 280 kg N ha–1). Perennial ryegrass (Lolium perenne) was planted 1 day after the application of biosolids and harvested after 120 days. The calculated amount of mineralisable organic N in ANDB was estimated to be 41% and 39% when applied to the clay loam and sandy loam soils, respectively; for ADB, it was 12% and 9%, respectively. These values indicate that the organic N mineralisation rates provided in the EPA Victoria guidelines (15% for ANDB and 25% for ADB) might not always be applicable. Also of note is that the values obtained for the each of the biosolids appear to be independent of the soil type.

The interaction between natural organic matter in raw waters and pesticide residues: a three dimensional excitation–emission matrix (3DEEM) fluorescence investigation

This paper examines the interaction between dissolved natural organic matter and pesticide residues, both of which are found in raw water sources, using three dimensional excitation-emission matrix (3DEEM) fluorescence spectroscopy. It was observed that pesticide residue at 0.1 mg L(-1) formed a complex with humic-like fluorophores that are commonly found in raw water samples. Applying 3DEEM fluorescence to investigate the humic fractions, it was found that identification of changes in water sources was possible, and, importantly, the presence of a number of pesticides was able to be determined. In addition, the formation of this complex, and the influence of soluble cations and anions upon it, was shown to impact the efficiency of analytical extraction procedures for pesticides; however, 3DEEM fluorescence could be an approach to account for such losses.

Assessment of the Viability of Vegetable Oil Based Fuels

This paper provides results of extensive trials using a 50/50 blend of unheated vegetable oil and diesel fuel in an unmodified vehicle on roads in Victoria, Australia. The work was inspired by the success of an on-road trial using 100 % waste vegetable oil in 2004 and positive indications in the literature. As well as being a sustainable alternative fuel, vegetable oil has the added safety advantage of having a much higher flash point than any other. Constant routes were used analogous in-part, to using prescribed drive cycles. Results were logged and bar-charts comparing fuel consumption for various fuel blends are presented. There was no clearly discernible difference (within the uncertainty of the measured data) in fuel consumption between the 50/50 blend and diesel fuel.