project sludge 4.0: the tuscany water utilities …

PROJECT SLUDGE 4.0: THE TUSCANY WATER UTILITIESTRANSITION TOWARD A CIRCULAR ECONOMY MODELFOR SLUDGE DISPOSAL

R. Gori1, S. Vitolo2, M. Aiello3, M. Manobianco4, A. Salimbeni4, T. Daddi5

1 Civil and Environmental Engineering Deparment – University of Florence2 Civil and Industrial Engineering Deparment – University of Pisa3 Acque Industrial s.r.l.4 Ingelia Italia s.r.l.5 ERGO s.r.l.

Sludge disposal in Tuscany

Gaia s.p.a. Publiacqua s.p.a.

Nuove acque s.p.a.

Acquedotto del Fiora s.p.a.

ASA s.p.a.

Acque s.p.a.

Geal s.p.a.

SLUDGE DISPOSAL: - annual sludge production from regional WWTPs: 110.000 ton- an increase to 130.000 ton/y is expected in the coming years- about 47% of sludge is produced by 11 plants

• Until 2016:• 30 – 40 % of biological sludge produced in Tuscany was disposed in agriculture (in Tuscany)• 60 – 70 % was treated instead in composting plants (both in Tuscany and outside the Region• 5 % was landfilled

Sludge disposal in Tuscany

• From September 2016 in Tuscany it is not possible to recovery the sludge in agriculture andsludge is disposed of outside the Region and also abroad

• Technological choices with sustainable costs and directed towards a circular economy give thechance to turn the wastewater treatment in an oppurtunity to recovery sludge through theirvalorization in an END OF WASTE process that creates safe products with added values.

The overall costs were about 10 M€/y

Increasing disposal costs are expected up to 18-20 M€/y

Transition of the sludge management system to a local circular economy shifting WWTPs in Water and Resources Recovery facilities (WRRFs) producing ‘feedstock’ for other processes

Within the framework of the Regional developing plan (FESR 2014 – 2020) the project titled:

Circular economy for the treatment and transformation of biosolids in biofertilizers (SLUDGE 4.0)

has been financed as one of the ‘Strategic projects for research and development’

Hydrothermal carbonization (HTC) will play a major role in this process. The construction of the first centralized HTC plant for sludge carbonization in Tuscany has already been approved.

Project SLUDGE 4.0

Materials

Hydrothermal carbonization

SLUDGE (10-25% DM):

▪ Primary

▪ Secondary

▪Digested(Aer/Anaer)

Hydrothermal carbonization

HTC

Gas

T = 180 - 250 °C

P = 10 - 40 bars

t = 0.5 - 20 hours

5 – 10 %

Solid(HYDROCHAR)

Liquid

Reaction conditions exert a significant effect on the characteristics of all the products obtained by HTC of sludge.

Temperature and reaction time are the most important parameters affecting the characteristics of both the hydrochar and the liquid phase.

The HHV is comparable to that of

lignite

Hydrothermal carbonization Hydrothermal carbonization

Dehydration and decarboxylation are the main reactions taking place during the HTC process changing the H:C and O:C ratios. Reactions of hydrolysis, polymerization, aromatization are also reported.

H/C and O/C ratios of hydrochar are comparable to that of low-grade coal and can therefore serve as a potential solid fuel

Hydrothermal carbonization Hydrothermal carbonization

Solid phase (Hydrochar) is the main product of the HTC process.

Y is variable depending on the characteristics of feedstock and HTC conditions. In the case of sludge Y is usually in the range 60 – 70%

Stabilization of the sludge affect the Y of the process

The hydrochar has a less hydrophilic character than that of the feedstock (lower H/C and O/C ratios)

Improved mechanical dewaterability of sludge after HTC (affect the energy density of the hydrochar and cost of transportation)

The yield in terms of mass is defined as:

Hydrothermal carbonization Hydrothermal carbonization - Solid phase

Solid combustible

Base material for producing adsorbents and activated carbons

Soilamendment

Alternative valorization pathways:

Solid phaseHydrothermal carbonization Hydrothermal carbonization - Solid phase

SLUDGE (10-25% DM):

▪ Primary

▪ Secondary

▪Digested(Aer/Anaer)

HTC

Gas

T = 180 - 250 °C

P = 10 - 40 bars

t = 0.5 - 20 hours

5 – 10 %

Solid(HYDROCHAR)

Liquid

- Rich in organic matter

- Potential impact on WWTP (especially in case of centralized HTC plants)

- Fractionation of COD

- Inhibition potential of autotrophic bacteria

- Potential benefit for denitrification

Hydrothermal carbonization Hydrothermal carbonization - Liquid phase

- Selective recovery of nutrients (N, P)

- Valorization as fertilizer (recovery of both macro- and micro-nutrients)

- Energy recovery with anaerobic treatment (methane prodction)

(from Escala et al., 2013)

Hydrothermal carbonization Hydrothermal carbonization - Liquid phase

✓ Acque Industriali s.r.l. (coordinator)

Hydrothermal carbonization Project SLUDGE 4.0 – Partners and goals



✓ Ingelia Italia S.p.A.


✓ Ingelia Italia s.p.a.


✓ National Interuniversity Consortium of Materials Science and Technology (INSTM) which will act through the following OUs:

- Civil and Environmental Engineering Dept. - University of Florence- Civil and Industrial Engineering Dept. - University of Pisa- Physical, earth and environmental Science Dept. - University of Siena






✓ ERGO s.r.l. Spin-off of Scuola Superiore S. Anna di Pisa







✓ NEXT GENOMICS s.r.l.








✓ P.H. s.r.l.







✓ P.H. s.r.l.


✓ TERRE LOGICHE s.r.l.

WP1 Application of HTC on sludge from WWTPs and detection of the optimal process strategy

MAIN GOAL: development of an integrated management system of sludge at regional level in order to create

centralized plants to treat sludge with HTC technology.

Activities:

1. Data collection, classification and modelling of the current wastewater teatment processes, quantities and

characterizations of sludge produced at regional level;

2. Identification and quantification of logistic flows (transports, storage and seasonality) required between wastewater

treatment processes and HTC;

3. Modelling of the integrated process of wastewater treatment and HTC to optimize the management of WWTPS at

regional level applying different working scenarios (with different SRTs and mixing different sludges);

4. Development of an integrated management system with HTC at regional level, based on plants simulation, to minimize

costs, energy consumptions and environmental impact;


WP2 Study, optimization and scale-up of HTC process on sludge from WWTPs

MAIN GOAL: optimization of working parameters of HTC sludge process in order to validate it as industrial

technology to recover sludge and to obtain safe, sustainable and efficient products for different applications.

Activities:

1. Study of the process and of the products changing working parameters;

2. Validation of HTC process at pilot-scale and industrial scale-up applying the feeding of sludge and the working

parameters chosen as optimal for the process;

3. Characterization of the solid/ liquid suspension (slurry) obtained from HTC reactor;

4. Characterization of the liquid fraction (chemical-physical, ecotoxicological and microbiological) downstream the

separation solid/ liquid;

5. Characterization of the solid fraction (chemical-physical,

eco-phyto-toxicological) downstream the separation

solid/ liquid (before and after drying).


WP3 Enhancement of possible applications of humid products (hydrochar suspension from mother

liquors, mother liquors) through circular economy process

MAIN GOAL: validation of applications of humid products obtained from HTC process on sludge, both as

solid/ liquid suspension and as liquid fraction downstream the separation solid/ liquid.

Activities:

1. Analysis of market and of national and European regulations;

2. Feasibility test of partial recovery of liquid fraction downstream the separation solid/ liquid inside the WWTP;

3. Modelling, synthesis and optimization of separation/ treatment processes to recover fertilizing substances from liquid

fraction and possible nutrients enhancement to obtain fertilizers;

4. Study and identification of uses of suitable suspensions and exahusted waters to develop a cycle of circular economy,

including agronomic tests (e.g. energy crops);


WP4 Valorisation of HYDROCHAR as material to apply in agri - food treatments at regional scale.

MAIN GOAL: enhancement of the C - rich fraction in order to obtain a material suitable for agri - food

applications at regional level.

Activities:

1. Analysis of market and of national and European regulations;

2. Identification at regional level of areas, which could potentially need the use of hydrochar, because of issues about

agronomic fertility and possible applications in environmental treatments;

3. Identification of the optimal characteristics of hydrochar for use, for upgrading and for functionalization of the

product. Optimization of hydrochar upgrading and functionalization;

4. Experimental campaigns to validate the main applications in agriculture and in the environment. Definition of a

manual for management and use;


WP5 Assessment of economic, environmental and social sustainability of the developed local model of

circular economy

MAIN GOAL: identification of the best solution and working modalities that assure the optimization of the

system from different points of view.

Activities:

1. Selection of working parameters of the integrated process and system implementation for their continuous and

automatic monitoring;

2. Development of a integrated management model at regional scale of WWTPs in order to minimize treatment costs,

water/energy consumptions, logistics and environmental sustainability;

3. Multidirectional communication between productive process and products in order to optimize and integrate

information along chain of value;

4. Overall evaluation of sustainability and circularity of the integrated system.



HTC plant 2

WWTP ith

HTC plant 1

Data input from WWTP

Data input from HTC plants

Riccardo Gori – Università di Firenze

[email protected]

Hydrothermal carbonization Acknowledgements

mailto:[email protected]

project sludge 4.0: the tuscany water utilities …

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