Study of food waste degradation in a simulated septic tank.

Septic systems are typically designed to treat domestic wastewater from households without access to centralized facilities. The installation of a food waste disposer (FWD) may increase the discharge of food waste (FW) into the wastewater; therefore, the installation of a FWD is discouraged in households that have a septic system. This study was conducted to determine how a typical dose of FW from a FWD can affect the performance of a septic system in terms of sewage treatment and solids accumulation. A 20-L control tank was compared with an experiment tank to which FW was added, increasing the amount of total suspended solids (TSS) by 31.3% and total chemical oxygen demands by 46.3% for a period of 110 days. Although the influent water quality changed dramatically, the effluent from the experiment tank had a substantially lower percentage increase in water quality parameters compared with the effluent from the control. It was found that in the experiment tank, 75.8% of FW TSS was degraded, whereas only 36.7% of sewage TSS was degraded, and that 18.8% of FW TSS and 44.9% of sewage TSS accumulated in the experiment tank. The addition of FW increased the scum accumulation, even though the dry matter of the scum layer was much less in quantity than the sludge layer. It also increased the lipid content in the sludge. The increase in the scum layer was mainly due to the increase in protein from the addition of the FW. Overall, compared with sewage TSS, FW TSS tends to be more biodegradable, which indicates that the impact on pumping frequency from adding FW will be insignificant.

Risk management, financial evaluation and funding for wastewater and stormwater reuse projects.

This paper has considered risk management, financial evaluation and funding in seven Australian wastewater and stormwater reuse projects. From the investigated case studies it can be seen that responsible parties have generally been well equipped to identify potential risks. In relation to financial evaluation methods some serious discrepancies, such as time periods for analysis, and how stormwater benefits are valued, have been identified. Most of the projects have required external, often National Government, funding to proceed. As National funding is likely to become less common in the future, future reuse projects may need to be funded internally by the water industry. In order to enable this the authors propose that the industry requires (1) a standard project evaluation process, and (2) an infrastructure funders' forum (or committee) with representation from both utilities and regulators, in order to compare and prioritise future reuse projects against each other.