Techno-economic evaluation of ozone-oxidation for sludge reduction at the full-scale. Comparison between the application to the return activated sludge (RAS) and the sludge digestion unit

Techno-Economic Evaluation of Ozone Application to Reduce Sludge Production in Small Urban WWTPs

“…This could explain the discrepancies in sludge reduction reported for similar values of SOD [10,21]. In some works, the flow rate of returned ozonated sludge is provided, but these data alone do not allow for calculation of the daily fraction of ozonated sludge [17,36]. As a consequence, the obtained results cannot be extrapolated to other operating conditions.…”

“…Of course, the convenience of reducing sludge production by means of ozonation strongly depends on the sludge-disposal taxes of each country. For example, in countries with high sludge-disposal taxes, reduced sludge production by ozonation is an economically viable strategy [17,35]. Even in cases where treatment costs are similar, the achievement of zero sludge production by ozonation could be an interesting operating strategy, since sludge-disposal regulations could change over time, and sludge disposal in landfills or agricultural applications of sludge could be restricted.…”

“…Until now, only ozonation and ultrasonic methods have been applied in full-scale urban WWTPs [16]. Ozonation promotes the disintegration and solubilization of biodegradable and non-biodegradable compounds in the sludge [17,18]. This process can be applied to a fraction of the sludge recycled from the secondary decanter to the biological reactor.…”

“…This procedure can generate a relevant net reduction in the amount of sludge that must be managed [10,12]. The ozone dosage is typically in the range of 0.01-0.74 g O 3 /g total suspended solids (TSS), resulting in a sludge reduction of between 10% and 100% [16,17,19]. It is important to note that literature has reported that the ozone-dose range should be between 0.03 and 0.05 g O 3 /g TSS to obtain an appropriate balance between sludge-reduction efficiency and operating costs [20,21].…”

“…This work is intended to represent a contribution to existing literature by providing information that can be useful in the evaluation and implementation of potential of sludgeozonation units as a way to reduce sludge production in small WWTPs. Previous studies have concentrated on the techno-economic evaluation of sludge-reduction technologies in the water line and/or sludge line of large WWTPs [2,[15][16][17], while economic assessments of sludge-reduction strategies for small urban WWTPs have not been studied.…”