The AquaCritox® hydrothermal oxidation technology was evaluated to treat food production waste from a sweet-packaging facility in Ireland. The waste stream known as “sweet water” was treated on-site using the AquaCritox NC demonstration unit to test the feasibility of hydrothermal oxidation at 250 – 300°C. The waste had a COD of 17 – 20 g/L, and a maximum COD destruction of 63% was achieved with 100% odour and colour removal. The results indicate that some of the organics in the waste are highly recalcitrant and would require the use of Supercritical Water Oxidation (AquaCritox SCWO) for complete COD destruction.
The Application
The feasibility of using the AquaCritox NC hydrothermal oxidation technology to treat the waste was evaluated by performing on-site testing. Continuous, steady-state operation was achieved, yielding complete odour and colour removal. The recalcitrant nature of the specific waste stream requires oxidation at supercritical water conditions (AquaCritox SCWO) for complete destruction of the waste material, yielding water sufficient for discharge or re-use within the facility.
Site Operations
The AquaCritox® SC demonstration unit was deployed to the site and the required utilities (Electricity, service water) were connected. The waste material was supplied in IBCs. Various operating conditions were investigated to see which conditions would yield the most desirable COD destruction. Reactor temperature, pressure and residence time were varied. The results indicated that varying the pressure from 100 bar to 155 bar did not have a significant impact on the COD destruction, although slightly higher destructions were observed at the higher pressure.
Average reactor temperature had the greatest impact on the achieved COD destruction, with performance improving from 34% destruction at 225°C to 63% at 280°C.
The Success
Thanks to the fully automated unit, the plant ran without issues for the duration of testing. The feasibility of using the sub-critical hydrothermal oxidation technology were successfully evaluated and the results show that 100% odour and colour removal can be achieved at these conditions. The results also showed that AquaCritox SCWO would be necessary for full COD destruction.
