An investigation into an innovative land application strategy for the sustainable management of biosolids
Creators: name: Beshah, Firew
Publisher: name: RMIT University
Year: 2024

description: This thesis describes an investigation into the use of nutrients from biosolids to produce two valuable crops (canola and oats) as sustainable biosolids management strategy which can be used for energy production and livestock fodder and hence avoids the problem of potential food contamination. <br><br>A two year field experiment was conducted at Western Water at Surbiton Park (WWSP) in 2006 and 2007 to compare the responses of soil and plants to the applications of anaerobically digested dewatered biosolids and composted biosolids in canola (Brassica napus L.) and oat (Avena sativa) under a crop rotation regime on a clay loam soil.<br><br>Results of the first year field experiment showed that the optimum canola seed yields were recorded at 25 t ds/ha and 30 t ds/ha of dewatered biosolids and composted biosolids application rates, respectively (p &lt;0.05) whereas, for the oat crop, the optimum seed yields were observed at the 25 t ds/ha and 50 t ds/ha for dewatered biosolids and composted biosolids, respectively (p &lt; 0.001 and p &lt; 0.05). In 2007 the optimum canola seed yields were recorded at 45 t ds/ha and 50 t ds/ha dewatered biosolids and composted biosolids rates respectively (p &lt; 0.001 and p &lt; 0.01). <br><br>Total N, P and S in dewatered biosolids and composted biosolids amended soils were significantly higher (p &lt; 0.05) than the conventionally fertilized and untreated control plots and increased following increased biosolids loading rates. Nitrogen loading rates from both biosolids types had negatively impacted the quality of canola seed oil, dewatered biosolids rates at 5 t/ha and composted biosolids rates at 50 t/ha produced the highest canola seed oil content (45.2 and 47.5 %), respectively, and thus these application rates would be ideal for farmers who need to maximize the oil content to benefit from the bonification scheme. In the canola-oats cropping sequence considerably higher concentrations of soil total N and Olsen-P and DTPA extractable ( Cu, Zn, Fe) were observed than in the oats-canola cropping sequence. The highest levels of total Cu and Zn recorded at the 65 and 70 t/ha dewatered biosolids and composted biosolids treated plots did not exceed the maximum EPA Victoria ceiling limits for Cu and Zn (300 and 250 µg/g) , for soils receiving biosolids for crop production (EPA Vic, 2004). The uptake of Cu and Zn by canola crop was substantially higher than the corresponding concentrations observed in oats leaves. Higher total N and extractable P concentrations were also observed in canola shoots than in oats treated with dewatered biosolids in both years of the trial suggesting that canola extracted more N and P which was consistent with the higher biomass yield than oats.<br><br>The study has demonstrated that biosolids can be effectively integrated into a rotational cropping system without detrimental effects on the receiving environment. The research showed that the strategy could be adopted as a sustainable management option to assist in the reduction of large biosolids stockpiles generated in wastewater treatment plants in Victoria receiving mainly domestic sewage.<br><br>The study has demonstrated that biosolids can be effectively integrated into a rotational cropping system without detrimental effects on the receiving environment. The research showed that the strategy could be adopted as a sustainable management option to assist in the reduction of large biosolids stockpiles generated in wastewater treatment plants in Victoria receiving mainly domestic sewage.<br>