Need help grading your biosolids? This new method can help

Posted 13 March 2017

BiosolidsWater utilities might get more than a whiff of 'the sweet smell of success' by adapting Sydney Water's new methodology for grading biosolids products.

Sydney Water has developed a Biosolids Quality Score (BQS) that aims to predict biosolids quality based on treatment processes and operational factors. 

“[It] can be used by plant managers to forecast biosolids quality during planned operational changes,” said one of the developers of the methodology, Sydney Water Service Planning Analyst Michael Young. 

“It will be used as part of a suite of tools to assist in grading biosolids products for end-use markets. We expect this to result in greater customer satisfaction, especially through reducing the likelihood of exposure to odorous product.”

The work came about after Sydney Water found that the characteristics of its biosolids varied considerably; even though they were all graded of equal quality (B for stabilisation), some still had issues with odour, transport and handling properties, such as stickiness. 

“To better differentiate the biosolids within the common grade, a qualitative assessment was undertaken for each of the biosolids products across 23 treatment plants,” stated the resultant paper The Sweet Smell of Success – Improving Biosolids Quality for Beneficial Reuse.

“The result of this assessment allocated each product to four quality groups based on risk allocation and cost of disposal, from B1 (better quality) to B4 (worse quality). The additional allocation allows for biosolids products to be distributed to the most appropriate reuse locations.”

Young said utilities around the country could apply the BQS, but it might need to be adapted to take specific treatment processes into consideration. 

“The BQS is best suited to biosolids that are treated in the conventional stabilisation methods [anaerobic and aerobic]. For new technologies such as thermal hydrolysis the model will need to be re-calibrated to provide an assessment of quality,” Young said. 

“The methodology can be applied by any utility to understand the effect key operational parameters will have on biosolids quality and provide a quantitative assessment of quality. It is important to note that this tool can be continuously improved.”

Young will be presenting more details on the model and its development at the upcoming Ozwater'17 conference. Register here now.