Tertiary Treatment of Ayr Municipal Wastewater using Bioremediation: A Pilot-Scale Study. A Report Prepared for the Burdekin Shire Council and the Burdekin Rangeland Reef Initiative

This joint DPI/Burdekin Shire Council project assessed the efficacy of a pilot-scale biological remediation system to recover Nitrogen (N) and Phosphorous (P) nutrients from secondary treated municipal wastewater at the Ayr Sewage Treatment Plant. Additionally, this study considered potential commercial uses for by-products from the treatment system. Knowledge gained from this study can provide directions for implementing a larger-scale final effluent treatment protocol on site at the Ayr plant. Trials were conducted over 10 months and assessed nutrient removal from duckweed-based treatments and an algae/fish treatment – both as sequential and as stand-alone treatment systems. A 42.3% reduction in Total N was found through the sequential treatment system (duckweed followed by algae/fish treatment) after 6.6 days Effluent Retention Time (E.R.T.). However, duckweed treatment was responsible for the majority of this nutrient recovery (7.8 times more effective than algae/fish treatment). Likewise, Total P reduction (15.75% reduction after 6.6 days E.R.T.) was twice as great in the duckweed treatment. A phytoplankton bloom, which developed in the algae/fish tanks, reduced nutrient recovery in this treatment. A second trial tested whether the addition of fish enhanced duckweed treatment by evaluating systems with and without fish. After four weeks operation, low DO under the duckweed blanket caused fish mortalities. Decomposition of these fish led to an additional organic load and this was reflected in a breakdown of nitrogen species that showed an increase in organic nitrogen. However, the Dissolved Inorganic Nitrogen (DIN: ammonia, nitrite and nitrate) removal was similar between treatments with and without fish (57% and 59% DIN removal from incoming, respectively). Overall, three effluent residence times were evaluated using duckweed-based treatments; i.e. 3.5 days, 5.5 days and 10.4 days. Total N removal was 37.5%, 55.7% and 70.3%, respectively. The 10.4-day E.R.T. trial, however, was evaluated by sequential nutrient removal through the duckweed-minus-fish treatment followed by the duckweed-plus-fish treatment. Therefore, the 70.3% Total N removal was lower than could have been achieved at this retention time due to the abovementioned fish mortalities. Phosphorous removal from duckweed treatments was greatest after 10.4-days E.R.T. (13.6%). Plant uptake was considered the most important mechanism for this P removal since there was no clay substrate in the plastic tanks that could have contributed to P absorption as part of the natural phosphorous cycle. Duckweed inhibited phytoplankton production (therefore reducing T.S.S) and maintained pH close to neutral. DO beneath the duckweed blanket fell to below 1ppm; however, this did not limit plant production. If fish are to be used as part of the duckweed treatment, air-uplifts can be installed that maintain DO levels without disturbing surface waters. Duckweed grown in the treatments doubled its biomass on average every 5.7 days. On a per-surface area basis, 1.23kg/m2 was harvested weekly. Moisture content of duckweed was 92%, equating to a total dry weight harvest of 0.098kg/m2/week. Nutrient analysis of dried duckweed gave an N content of 6.67% and a P content of 1.27%. According to semi-quantitative analyses, harvested duckweed contained no residual elements from the effluent stream that were greater than ANZECC toxicant guidelines proposed for aquaculture. In addition, jade perch, a local aquaculture species, actively consumed and gained weight on harvested duckweed, suggesting potential for large-scale fish production using by-products from the effluent treatment process. This suggests that a duckweed-based system may be one viable option for tertiary treatment of Ayr municipal wastewater. The tertiary detention lagoon proposed by the Burdekin Shire Council, consisting of six bays approximately 290 x 35 metres (x 1.5 metres deep), would be suitable for duckweed culture with minor modification to facilitate the efficient distribution of duckweed plants across the entire available growing surface (such as floating containment grids). The effluent residence time resulting from this proposed configuration (~30 days) should be adequate to recover most effluent nutrients (certainly N) based on the current trial. Duckweed harvest techniques on this scale, however, need to be further investigated. Based on duckweed production in the current trial (1.23kg/m2/week), a weekly harvest of approximately 75 000kg (wet weight) could be expected from the proposed lagoon configuration under full duckweed production. A benefit of the proposed multi-bay lagoon is that full lagoon production of duckweed may not be needed to restore effluent to a desirable standard under the present nutrient load, and duckweed treatment may be restricted to certain bays. Restored effluent could be released without risk of contaminating the receiving waterway with duckweed by evacuating water through an internal standpipe located mid-way in the water column.

Honeydew as a source of nutrition for Lysiphlebus testaceipes (Cresson) (Hymenoptera: Braconidae): Effect of adult diet on lifespan and egg load

Parasitoid survival and fecundity is generally enhanced with access to carbohydrate food sources. In many agricultural ecosystems, there is often a scarcity of suitable carbohydrates for parasitoids. This study compared the suitability of aphid honeydew and buckwheat nectar as diet for the aphid parasitoid Lysiphlebus testaceipes. Wasp lifespan and egg load were both increased with access to carbohydrates, but no differences were detected between the various carbohydrates diets tested. As aphid honeydew is a sufficient source of nutrition and L.testaceipes is a short-lived species, adding additional sources of carbohydrates like floral nectar strips to the agricultural landscape is unlikely to significantly increase the biological control exerted by L.testaceipes. © 2012 Australian Entomological Society.

Pig effluent-P application can increase risk of P transport: two case studies

Land application of piggery effluent (containing urine, faeces, water, and wasted feed) is under close scrutiny as a potential source of water resource contamination with phosphorus (P). This paper investigates two case studies of the impact of long-term piggery effluent-P application to soil. A Natrustalf (Sodosol) at P1 has received a net load of 3700 kg effluent P/ha over 19 years. The Haplustalf (Dermosol) selected (P2) has received a net load of 310 000 kg P/ha over 30 years. Total, bicarbonate extractable, and soluble P forms were determined throughout the soil profiles for paired (irrigated and unirrigated) sites at P1 and P2, as well as P sorption and desorption characteristics. Surface bicarbonate (PB, 0 - 0.05 m depth) and dilute CaCl2 extractable molybdate-reactive P (PC) have been significantly elevated by effluent irrigation (P1: PB unirrigated 23±1, irrigated 290±6; PC unirrigated 0.03±0.00, irrigated 23.9±0.2. P2: PB unirrigated 72±48, irrigated 3950±1960; PC unirrigated 0.7±0.0, irrigated 443±287 mg P/kg; mean±s.d.). Phosphorus enrichment to 1.5 m, detected as PB, was observed at P2. Elevated concentrations of CaCl2 extractable organic P forms (POC; estimated by non-molybdate reactive P in centrifuged supernatants) were observed from the soil surface of P1 to a depth of 0.4 m. Despite the extent of effluent application at both of these sites, only P1 displayed evidence of significant accumulation of POC. The increase in surface soil total P (0 - 0.05 m depth) due to effluent irrigation was much greater than laboratory P sorption (>25 times for P1; >57 times for P2) for a comparable range of final solution concentrations (desorption extracts ranged from 1-5 mg P/L for P1 and 50-80 mg P/L for P2). Precipitation of sparingly soluble P phases was evidenced in the soils of the P2 effluent application area.

No-tillage and nitrogen application affects the decomposition of 15N-labelled wheat straw and the levels of mineral nitrogen and organic carbon in a Vertisol

No-tillage (NT) practice, where straw is retained on the soil surface, is increasingly being used in cereal cropping systems in Australia and elsewhere. Compared to conventional tillage (CT), where straw is mixed with the ploughed soil, NT practice may reduce straw decomposition, increase nitrogen immobilisation and increase organic carbon in the soil. This study examined 15N-labelled wheat straw (stubble) decomposition in four treatments (NT v. CT, with N rates of 0 and 75 kg/ha.year) and assessed the tillage and fertiliser N effects on mineral N and organic C and N levels over a 10-year period in a field experiment. NT practice decreased the rate of straw decomposition while fertiliser N application increased it. However, there was no tillage practice x N interaction. The mean residence time of the straw N in soil was more than twice as long under the NT (1.2 years) as compared to the CT practice (0.5 years). In comparison, differences in mean residence time due to N fertiliser treatment were small. However, tillage had generally very little effect on either the amounts of mineral N at sowing or soil organic C (and N) over the study period. While application of N fertiliser increased mineral N, it had very little effect on organic C over a 10-year period. Relatively rapid decomposition of straw and short mean residence time of straw N in a Vertisol is likely to have very little long-term effect on N immobilisation and organic C level in an annual cereal cropping system in a subtropical, semiarid environment. Thus, changing the tillage practice from CT to NT may not necessitate additional N requirement unless use is made of additional stored water in the soil or mineral N loss due to increased leaching is compensated for in N supply to crops.

Using wheat flour in the production of organic banana prawns

Banana prawn (Fenneropenaeus merguiensis) juveniles (1-2 g) were compared for survival, growth and condition after feeding in tanks over one month with several simple diets based on organically certified whole wheat flour. All feeds were applied once per day at 6% of the starting body weight, and produced high survival (>94%). A commercial Australian prawn feed used as the control diet produced the highest (P<0.05) growth (101% weight gain) and condition measured as the length of antennae (13.2 cm). The unfed control had significantly (P<0.05) lower survival (56%), and resulted in a weight loss (3.1%) and the shortest antennae (9.4 cm). Adding free flour to tanks produced lower (P<0.05) growth (6.9%) and shorter (P<0.05) antennae (10.3 cm) than adding pelletised flour with low levels (dry weight) of additional nutritional substances and feed attractants (chicken’s whole egg: 1.5%, polychaete slurry: 1.1% and 6.8%, molasses: 4.2%). Rolling the flour into a dough ball also appeared to marginally improve its direct utilisation by the prawns. These results are considered within the context of appropriate nutrition for Penaeids and successfully producing certified organic prawns in Australia.

Organic diet development for black tiger prawns

The survival and growth of black tiger prawn (Penaeus monodon) juveniles (~3.3 g) were compared after feeding in tanks over one month with several prepared diets based on organically certified ingredients. The extrusion process in the manufacture of pelletised experimental diets was similar to processes used in commercial plants and was closely documented. The daily feeding rate (6% of starting mean body weight) was split equally into two feeds, one in the morning and one in the afternoon. All diets tested produced high survival (97-100%). A widely-used commercial Australian prawn feed was used as a control diet. It contained 41.2% protein with 29.5 g kg-1 lysine, and produced the highest (P<0.05) growth (117% weight gain). Three of the experimental organic diets tested (namely, 1. wheat + soy, 2. pig weaner diet + soy, and 3. pig weaner diet + dried fish waste) produced moderate growth (73–77% weight gain). These contained 33%, 36% or 31% protein, respectively, and produced better (P<0.05) growth than diets utilising a range of other prospective ingredients (eg: wheat + dried scallop gut, wheat + fish waste, wheat + chickpea, or wheat + macadamia meal, containing 23%, 25%, 29% or 24% protein, respectively). An unfed control-treatment produced the lowest (P<0.05) growth (4% weight gain). The water stability of the experimental diets that produced the best growth was poorer than the commercial diet, suggesting that improvements in this aspect of these organic feed’s manufacture could result in additional performance benefits and possibly reduced feed wastage. Analyses revealed a linear relationship between diet performance (in terms of weight gains) and the protein and lysine contents of diets. About 70% of diet performance was explained by these factors. The superior performance of the commercial diet could be attributed primarily to its formulation using mainly marine proteins, as well as a range of other unknown factors (commercial in confidence). These other factors range from use of feed attractants, better knowledge of ingredient nutrient availability, different extrusion conditions and the use of other unspecified micro-nutrients not present in the experimental diets. The organic diets studied still require a degree of fine-tuning before structured commercial uptake. This would sensibly include further detailed investigations of the composition and nutrient availabilities of these and other organic dietary ingredients, and refinement of the extrusion process for formulated diets.

Influence of soil organic amendments on suppression of the burrowing nematode, Radopholus similis, on the growth of bananas.

Radopholus similis is a major constraint to banana production in Australia and growers have relied on nematicides to manage production losses. The use of organic amendments is one method that may reduce the need for nematicides, but there is limited knowledge of the influence of organic amendments on endo-migratory nematodes, such as R. similis. Nine different amendments, namely, mill mud, mill ash, biosolids, municipal waste compost, banana residue, grass hay, legume hay, molasses and calcium silicate were applied to the three major soil types of the wet tropics region used for banana production. The nutrient content of the amendments was also determined. Banana plants were inoculated with R. similis and grown in the soil-amendment mix for 12-weeks in a glasshouse experiment. Assessments of plant growth, plant-parasitic nematodes and soil nematode community characteristics were made at the termination of the experiment. Significant suppression of plant-parasitic nematodes occurred in soils amended with legume hay, grass hay, banana residue and mill mud relative to untreated soil. These amendments were found to have the highest N and C content. The application of banana residue and mill mud significantly increased shoot dry weight at the termination of the experiment relative to untreated soil. Furthermore, the applications of banana residue, grass hay, mill mud and municipal waste compost increased the potential for suppression of plant-parasitic nematodes through antagonistic activity. The application of amendments that are high in C and N appeared to be able to induce suppression of plant-parasitic nematodes in bananas, by developing a more favourable environment for antagonistic organisms.

Organic inputs, tillage and rotation practices influence soil health and suppressiveness to soilborne pests and pathogens of ginger.

A field experiment was established in which an amendment of poultry manure and sawdust (200 t/ha) was incorporated into some plots but not others and then a permanent pasture or a sequence of biomass-producing crops was grown with and without tillage, with all biomass being returned to the soil. After 4 years, soil C levels were highest in amended plots, particularly those that had been cropped using minimum tillage, and lowest in non-amended and fallowed plots, regardless of how they had been tilled. When ginger was planted, symphylans caused severe damage to all treatments, indicating that cropping, tillage and organic matter management practices commonly used to improve soil health are not necessarily effective for all crops or soils. During the rotational phase of the experiment, the development of suppressiveness to three key pathogens of ginger was monitored using bioassays. Results for root-knot nematode (Meloidogyne javanica) indicated that for the first 2 years, amended soil was more suppressive than non-amended soil from the same cropping and tillage treatment, whereas under pasture, the amendment only enhanced suppressiveness in the first year. Suppressiveness was generally associated with higher C levels and enhanced biological activity (as measured by the rate of fluorescein diacetate (FDA) hydrolysis and numbers of free-living nematodes). Reduced tillage also enhanced suppressiveness, as gall ratings and egg counts in the second and third years were usually significantly lower in cropped soils under minimum rather than conventional tillage. Additionally, soil that was not disturbed during the process of setting up bioassays was more suppressive than soil which had been gently mixed by hand. Results of bioassays with Fusarium oxysporum f. sp. zingiberi were too inconsistent to draw firm conclusions, but the severity of fusarium yellows was generally higher in fumigated fallow soil than in other treatments, with soil management practices having little impact on disease severity. With regard to Pythium myriotylum, biological factors capable of reducing rhizome rot were present, but were not effective enough to suppress the disease under environmental conditions that were ideal for disease development.

Growing organic prawns - in inland saline waters

This report details the results of research into organic production of prawns in Australia. This has involved activities and experiments over two years at several sites and using a multidisciplinary approach. This includes farm trials at an inland demonstration prawn farm which solely utilises saline bore water, sample collection from two commercial prawn farms in coastal regions of south-eastern Queensland, replicated feed trials at one of DPI&F’s aquaculture research stations, specified feed manufacture at the laboratories of University of Queensland, and packaging and product storage trials and food analyses at two of DPI&F’s food technology laboratories. This work was designed to investigate and assist in the possible adoption of organic procedures by the Australian prawn farming industry. The import from Asia of cheaply produced prawns has forced all Australian prawn farmers to review their marketing procedures. Additionally investors are becoming increasingly concerned at the prospects for the expansion of this industry in Australia. Since the competition of seafood products in the marketplace is increasing on a global basis, alternate products are being investigated by those wishing to maintain and/or grow their market share. The premium paid for organic food products would hopefully provide an economic incentive for farmers to convert to organic production systems, with an added advantage that the standards that apply have beneficial implications also for the social and environmental practices of industry.

Estimating mineralisation of organic nitrogen from biosolids and other organic wastes applied to soils in subtropical Australia

One major benefit of land application of biosolids is to supply nitrogen (N) for agricultural crops, and understanding mineralisation processes is the key for better N-management strategies. Field studies were conducted to investigate the process of mineralisation of three biosolids products (aerobic, anaerobic, and thermally dried biosolids) incorporated into four different soils at rates of 7-90 wet t/ha in subtropical Queensland. Two of these studies also examined mineralisation rates of commonly used organic amendments (composts, manures, and sugarcane mill muds). Organic N in all biosolids products mineralised very rapidly under ambient conditions in subtropical Queensland, with rates much faster than from other common amendments. Biosolids mineralisation rates ranged from 30 to 80% of applied N during periods ranging from 3.5 to 18 months after biosolids application; these rates were much higher than those suggested in the biosolids land application guidelines established by the NSW EPA (15% for anaerobic and 25% for aerobic biosolids). There was no consistently significant difference in mineralisation rate between aerobic and anaerobic biosolids in our studies. When applied at similar rates of N addition, other organic amendments supplied much less N to the soil mineral N and plant N pools during the crop season. A significant proportion of the applied biosolids total N (up to 60%) was unaccounted for at the end of the observation period. High rates of N addition in calculated Nitrogen Limited Biosolids Application Rates (850-1250 kg N/ha) resulted in excessive accumulation of mineral N in the soil profile, which increases the environmental risks due to leaching, runoff, or gaseous N losses. Moreover, the rapid mineralisation of the biosolids organic N in these subtropical environments suggests that biosolids should be applied at lower rates than in temperate areas, and that care must be taken with the timing to maximise plant uptake and minimise possible leaching, runoff, or denitrification losses of mineralised N.

What determines soil organic carbon stocks in the grazing lands of north-eastern Australia?

This study aimed to unravel the effects of climate, topography, soil, and grazing management on soil organic carbon (SOC) stocks in the grazing lands of north-eastern Australia. We sampled for SOC stocks at 98 sites from 18 grazing properties across Queensland, Australia. These samples covered four nominal grazing management classes (Continuous, Rotational, Cell, and Exclosure), eight broad soil types, and a strong tropical to subtropical climatic gradient. Temperature and vapour-pressure deficit explained >80% of the variability of SOC stocks at cumulative equivalent mineral masses nominally representing 0-0.1 and 0-0.3m depths. Once detrended of climatic effects, SOC stocks were strongly influenced by total standing dry matter, soil type, and the dominant grass species. At 0-0.3m depth only, there was a weak negative association between stocking rate and climate-detrended SOC stocks, and Cell grazing was associated with smaller SOC stocks than Continuous grazing and Exclosure. In future, collection of quantitative information on stocking intensity, frequency, and duration may help to improve understanding of the effect of grazing management on SOC stocks. Further exploration of the links between grazing management and above- and below-ground biomass, perhaps inferred through remote sensing and/or simulation modelling, may assist large-area mapping of SOC stocks in northern Australia. © CSIRO 2013.

Integrating organic matter into banana plantation in North Queensland: the effects on soil properties

The major banana production areas in Australia are particularly sensitive to environments due to their close proximity to areas of World Heritage rainforest and the Great Barrier Reef catchment. Management of soil quality, nutrients and pesticides are vital to maintaining the integrity of these sensitive areas. Studies on cropping systems have suggested that integrating organic matter into ground cover management would improve the quality of soil under banana cultivation. In this study, an alternative management practice for bananas, which addresses the management of organic matter and fertiliser application, was assessed and compared to the conventional practice currently employed in the banana industry. Several chemical, physical and biological soil parameters were measured including: pH, electrical conductivity, water stable aggregates, bulk density, water filled pore space, porosity, water content, fluorescein diacetate hydrolyis (FDA) and beta-glucosidase activity. The alternative management practice did not have a significant impact of the production and growth of bananas but overall improved the quality of the soil. Although some differences were observed, the chemical and physical soil characteristics did not differ dramatically between the two management systems. The addition of organic matter resulted in the soil under alternative practice having higher FDA and beta-glucosidase levels, indicating higher microbial activity. The integration of organic matter into the management of bananas resulted in positive benefits on soil properties under bananas, however, methods of maintaining organic matter in the soil need to be further researched.

The effect of pasture utilization rate on stocks of soil organic carbon and total nitrogen in a semi-arid tropical grassland

The influence of grazing management on total soil organic carbon (SOC) and soil total nitrogen (TN) in tropical grasslands is an issue of considerable ecological and economic interest. Here we have used linear mixed models to investigate the effect of grazing management on stocks of SOC and TN in the top 0.5 m of the soil profile. The study site was a long-term pasture utilization experiment, 26 years after the experiment was established for sheep grazing on native Mitchell grass (Astrebla spp.) pasture in northern Australia. The pasture utilization rates were between 0% (exclosure) and 80%, assessed visually. We found that a significant amount of TN had been lost from the top 0.1 m of the soil profile as a result of grazing, with 80% pasture utilization resulting in a loss of 84 kg ha−1 over the 26-year period. There was no significant effect of pasture utilization rate on TN when greater soil depths were considered. There was no significant effect of pasture utilization rate on stocks of SOC and soil particulate organic carbon (POC), or the C:N ratio at any depth; however, visual trends in the data suggested some agreement with the literature, whereby increased grazing pressure appeared to: (i) decrease SOC and POC stocks; and, (ii) increase the C:N ratio. Overall, the statistical power of the study was limited, and future research would benefit from a more comprehensive sampling scheme. Previous studies at the site have found that a pasture utilization rate of 30% is sustainable for grazing production on Mitchell grass; however, given our results, we conclude that N inputs (possibly through management of native N2-fixing pasture legumes) should be made for long-term maintenance of soil health, and pasture productivity, within this ecosystem.

Association between feline immunodeficiency virus (FIV) plasma viral RNA load, concentration of acute phase proteins and disease severity

Veterinarians have few tools to predict the rate of disease progression in FIV-infected cats. In contrast, in HIV infection, plasma viral RNA load and acute phase protein concentrations are commonly used as predictors of disease progression. This study evaluated these predictors in cats naturally infected with FIV. In older cats (>5 years), log10 FIV RNA load was higher in the terminal stages of disease compared to the asymptomatic stage. There was a significant association between log10 FIV RNA load and both log10 serum amyloid A concentration and age in unwell FIV-infected cats. This study suggests that viral RNA load and serum amyloid A warrant further investigation as predictors of disease status and prognosis in FIV-infected cats.