X Sludge Conference: sewage sludge management in Andalusia

DECEMBER 11, 2023

Last November 23rd, the X Sludge Management and Treatment Conference, organized by the Environmental Biotechnology group of the University of Barcelona on a biannual basis, was held online.

You can consult the program of the X Sludge Conference at his official website.

Sewage sludge management in Andalusia

teCH4+ presented, through a series of practical cases, an overview of sewage sludge management in Andalusia since, in August 2018, new sludge regulation was published that prescribes the following treatments for the agricultural valorisation of WWTP sludge: composting, thermophilic anaerobic digestion, mesophilic anaerobic digestion preceded by a thermal treatment (thermal hydrolysis was explicitly included later on), aerobic stabilization, stabilization with lime and thermal drying.

Different actors faced this legislative challenge in different ways, as illustrated by three practical cases:

1. Seville: in parallel to the rationalization of its large WWTPs, which are reduced from four to two, an integrated sludge management model was articulated around two basic pillars: co-digestion and thermal hydrolysis technology to enhance mesophilic anaerobic digestion.

2. Malaga: after an alternative analysis, a comprehensive redesign of the sludge line and low-temperature thermal drying was chosen.

3. Other WWTPs: the majority of Andalusian WWTPs made the decision to compost their sludge in external plants. This means, for medium/large treatment plants and with prevalent composting price in the €30-50/ton range, a high management cost that can be significantly reduced by implementing thermal processes such as hygienisation.

The other alternative treatments (thermophilic anaerobic digestion, aerobic stabilization and lime stabilization) have not been implemented anywhere, so these three cases cover the entire spectrum of practical options.

Looking to the future, sludge management will be conditioned by the requirements imposed by the European Directive on urban wastewater treatment on critical issues such as N and P limits or energy self-sufficiency. And, in any case, it seems indisputable that the role of nutrient elimination/recovery processes and thermal processes will be key in the biorefineries of the future.

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