What Advanced Treatments Can Be Used to Minimize the Production of Sewage Sludge in WWTPs?

Maria Cristina Collivignarelli,Marco Carnevale Miino,Alessandro Abbà,Vincenzo Torretta

doi:10.3390/app9132650

Maria Cristina Collivignarelli, Marco Carnevale Miino + Show 2 more

Open Access

https://doi.org/10.3390/app9132650

Copy DOI

Abstract

Similar to other types of waste, sewage sludge (SS) must be minimized, not only to respect the European Directive 2018/851 on waste, but also because the cost of sludge management is approximately 50% of the total running costs of a wastewater treatment plant (WWTP). Usually, minimization technologies can involve sewage sludge production with three different strategies: (i) adopting a process in the water line that reduces the production of sludge; (ii) reducing the water content (dewatering processes) or (iii) reducing the fraction of volatile solids (stabilization). This review, based on more than 130 papers, aims to provide essential information on the process, such as the advantages, the drawbacks and the results of their application. Moreover, significant information on the technologies still under development is provided. Finally, this review reports a discussion on the impact of the application of the proposed processes in the sludge line on a WWTP with a capacity exceeding 100,000 population equivalent (PE).

Highlights

Sewage sludge (SS) is a mixture of organic and inorganic matter and its composition strongly depends on the treatment and on the wastewater origin [1]
Minimization technologies can involve sewage sludge production with three different strategies: (i) adopting a process in the water line that reduces the production of sludge; (ii) reducing the water content or (iii) reducing the fraction of volatile solids
Assuming the application of proposed processes, for example, on the urban wastewater treatment plant (WWTP) with a capacity higher than 100,000 population equivalent (PE), this would cover more than 50% of the total load treated in EU28 [135]

Summary

Introduction

Sewage sludge (SS) is a mixture of organic and inorganic matter and its composition strongly depends on the treatment and on the wastewater origin [1]. It can be composed of primary sludge, derived from primary sedimentation and formed by suspended sedimentary materials, secondary sludge, made up of excess biomass and, tertiary sludge, obtained in the advanced wastewater treatment stages, when nutrient (nitrogen and phosphorus) removal is required [2]. 50% [5], with an estimate of more than 13 million Mg of dry matter in 2020 According to these data, developing urgent and effective approaches to reduce and recover SS becomes a priority [6,7]

Results

Discussion

Conclusion