Full scale experiences with TurboTec continuous thermal ...€¦ · continuous TurboTec® THP system is introduced, this process offers the opportunity of lower investment and substantially

19th European Biosolids & Organic Resources Conference & Exhibition

www.european-biosolids.com

Organised by Aqua Enviro

Full scale experiences with TurboTec® continuous thermal hydrolysis at

WWTP Venlo (NL) and Apeldoorn (NL)

Pereboom , J.1 Luning, L1. Hol, A1. van Dijk, L1. and de Man, A.W.A,2 1Sustec Consulting and Contracting, Wageningen (NL), 2 WBL Roermond

Corresponding Author: J. Pereboom Tel.. ++31 317 763 749 Email [email protected]

Abstract

The degradation by anaerobic digestion of waste activated sludge (WAS) can be

improved by the novel TurboTec® continuous thermal hydrolysis process (c-THP)

developed by the Dutch contractor Sustec. The first full scale plant was started up in the

beginning of 2013 at the WWTP Venlo in the Netherlands. During this initial start-up some

serious scale-up problems were encountered such as severe steam hammer,

unexpected high pressure drops and poor heat transfer. These experiences triggered the

development of an adapted flow scheme including a new process for heat transfer.

The performance of the new system is presented in terms of required pre-treatment

(dewatering), overall energy demand and steam demand in particular, digester

behaviour ( biogas production and VSS-reduction) and the effect on final dewatering.

The data are derived from the plant in Venlo (7000 t TSS/y), where the system is operated

since April 2014. Furthermore, a brief introduction is paid to the second full-scale plant at

WWTP Apeldoorn (13.000 t TSS/y).

Keywords

Thermal hydrolysis, digestion, biogas, sludge treatment, energy efficiency, biomass,

scale-up, heat recovery, disintegration

Introduction

The Thermal Hydrolysis Process (THP) substantially reduces the treatment and disposal

costs of sludge and several water authorities have adopted this process in recent years.

In comparison to the conventional batch-hydrolysis systems, the novel and patented

continuous TurboTec® THP system is introduced, this process offers the opportunity of

lower investment and substantially lower operating costs. Two Dutch Waterboards have

adopted this technology and have ordered full scale plants.

Thermal hydrolysis is a pre-treatment step for surplus sludge and other biomass streams to

improve the biogas production during anaerobic digestion. The hydrolysis is done at

temperatures of 140~180°C and at pressures of 4~8 Bar for a period of 30~60 minutes. This

treatment results in the break-up of cells and the hydrolysis of complex molecules into

smaller compounds, while also the viscosity of the sludge significantly reduces. The

overall effects in anaerobic digestion are a higher conversion of organic compounds

into biogas, shorter retention times and higher volumetric loading rates. Finally, the

dewatering, after digestion, is substantially improved. In practise up to 30~35% more

biogas is generated in mesophilic digestion of surplus sludge or WAS (waste activated

http://www.european-biosolids.com/

mailto:JPM@




sludge). The effect on the dewatering is even more pronounced, since the amount of

sludge cake can be reduced by as much as 40% for WAS.

For water authorities the increased amount of biogas is interesting, since this is a valuable

source of green energy. But the main financial driving force for introducing THP, are the

reduced disposal costs of the sludge cake and/or avoided costs for additional digester

capacity. Especially, when the sludge cake is incinerated, the payback time of a THP

installation will be relatively short (4~7 years). Thermal hydrolysis can also be used as a

thermal treatment to achieve sludge cake which meets the Class-A biosolids

requirements. Thermal hydrolysis reduces the required digestion time and thus digestion

volume, resulting in reduced investment costs in green-field digestion projects. In retrofit

situations thermal hydrolysis increases the capacity of the available digestion volume

with approximately 50%, facilitating centralized sludge management. Hydrolysis also

results in the additional release of nutrients, which will have to be handled in side stream

or waterline removal system. Also the amount of residual COD in the final effluent of a

wastewater treatment plant could increase due to the thermal hydrolysis, although this

effect can be mitigated by operating the THP at moderate temperatures (≈140°C).

The TurboTec approach

Considering the potential of THP the Dutch company Sustec decided to develop a novel

cost effective and marketable process. In line with the development philosophy this was

built up from lab-practice to pilot plant operation to full-scale design and construction.

The lab scale results for various biosolids streams on the effect of THP treatment allowed

to convince clients of the potential of the technology and the justification of performing

pilot plant research under site specific operational conditions. In addition to further

insight in the performance of the technology, pilot plant research also allows for scale-up

of the proposed equipment such as heat transfer and fluid handling.

In designing the pilot plant it was decided to take a continuous operation as a starting

point, as an alternative to the batch wise operation commonly applied at that time. The

arguments for the preference of continuous operation were amongst others:

Appropriateness, as the production of sludge is a continuous all- round the year

process, its treatment is best done in a similar way;

Efficiency, continuous operation for one does not require different process-steps

to be performed in a sequential order resulting in periods where part of the

equipment is not active. Because of the efficient utilisation of process- and

auxiliary equipment, including pumps and steam production units, of smaller

capacity can be chosen. Overall this results in a smaller footprint, lower

investment costs and increased benefits of scale.

Reduction of the heat demand, specifically for steam. In batch-wise systems heat

is recovered by regeneration of the injected steam (flash-steam). The flash steam

is released when allowing the hydrolysed sludge to depressurise and is used to

heat the incoming sludge. This way of operation has a fundamental limitation in

that it can only cool the hydrolysed sludge to just over 100 °C. Even then not all

of the available heat between the hydrolysis temperature and 100 °C can be





utilised. In continuous operation the application of appropriate heat exchangers

would overcome this limitation, making the process more efficient.

Development of the pilot plant

In order to demonstrate the effect of thermal hydrolysis on pilot scale, the design of the

pilot plant did not only include a thermal hydrolysis operation, but also the application of

two digesters for parallel operation. In that way a simultaneous digestion of both

hydrolysed and untreated sludge could be investigated.

The TurboTec® pilot installation has successfully been operated at a number of WWTP’s in

the Netherlands and abroad: WWTP’s Venlo, Hoensbroek, Geesterambacht, Amersfoort

(NL) and ARA Limmattal and Neugut (CH) under different conditions.

In recent years Dutch Waterboards have shown in increased interest in the potential of

sludge disintegration technologies. This has led to a number of research projects

coordinated by STOWA, the Dutch foundation for applied research in water

management. In one of these projects the results of the TurboTec pilot plant at the WWTP

Amersfoort were compared with pilot plant trials performed by Cambi at the WWTP

Hengelo (STOWA 2012). Both tests were performed using a parallel set-up of digesters for

untreated and hydrolysed sludge. During the tests the VS-reduction and biogas

production were monitored. The tests ran for several months and different loading rates

were investigated.

Although the differences in the set-up of the experiments require caution in comparing

the results, the comparative results were striking. In both cases a specific biogas

production of 450 l/kg VSfed was registered for the hydrolysed samples in comparison to

335 – 355 l/kg VSfed for the untreated sludge. This suggests an improved degradation by a

factor 1,27 -1.34. The results indicate that for continuous and batch wise operation an

equal improvement of degradation can be achieved. These results refer to the

treatment of a mixture of primary sludge and WAS with a contribution of WAS of 70 – 80%.

Apart from a confirmation of the expected performance improvement, the operation of

the pilot plant also offered valuable experience with the equipment applied. A point of

specific interest was the transfer of heat at high temperature to reach the desired

hydrolysis temperature. For the pilot plant a combination of steam injection and

recirculation over a heat exchanger with thermal oil as medium was studied. Specifically

the application of the hot thermal oil led to scaling and caking of solids in the internal of

the heat exchanger. The increased wall temperature of 140 – 160 °C was considered

responsible for this phenomenon. The full scale TurboTec® plant therefore applies direct

steam injection for reaching the desired hydrolysis temperature. In this way also sludge

pumps do not have to be operated at temperatures close to the hydrolysis temperature.

Design considerations

Viscosity

To limit the heat demand for thermal hydrolysis the volume of the sludge to be treated is

generally reduced by pre-thickening the sludge. Apart from the increase in TS-content,

this also has a strong effect on the viscosity of the sludge. Figure 1 gives a comparison





between samples of 10 – 11% TS and a percentage of 6% TS that is not unusual in

conventional anaerobic digestion. Sludge behaves as a non-Newtonian liquid and

shows effects of “shear thinning”, if the mixing (shear rate) is more intense , the viscosity

will decrease, this relationship is presented in figure 1.

0,00

10,00

20,00

30,00

40,00

50,00

60,00

70,00

80,00

0 20 40 60 80 100 120 140 160

Vis

cosi

ty (P

a.s)

Shear rate (/s)

raw sludge 10,9 % TS

raw sludge 10,1 % TS

raw sludge 5,9 % TS

Figure 1: Viscosities of varies sludges at increased shear rates.

This increase in viscosity of a factor 6, makes it very difficult to handle the sludge in a heat

exchanger. The higher viscosity will result in extreme pressure losses and a poor heat

transfer.

Viscosity is strongly related to the temperature. In figure 2 this effect is shown for a WAS

sample of 11 % TS. The figure indicates that the effect of temperature on viscosity is

specifically strong in the range between 15 and 60 °C. Above this temperature the effect

is less pronounced

0

5

10

15

20

25

30

0 25 50 75 100 125

Vis

co

sit

y

(Pa

.s)

Shear rate (s-1)

15 °C

40°C

60°C

80°C

100°C

Figure 2: Viscosity as function of shear rate of raw WAS at different temperatures.





Raising the temperature of raw sludge at 11%Ds above 50-60°C, substantially reduces the

viscosity by approximately 50%. In order to make use of this phenomenon a different

way of heat transfer than conventional heat exchangers is required. This is possible by

making use of the effect that thermal hydrolysis has on the viscosity of sludge.

The most striking change in sludge characteristic during hydrolysis is the reduction in

viscosity. This is illustrated in figure 3. The top line represents the raw WAS and the bottom

line the hydrolysed material. Both samples have the same TS-content. From figure 3 it can

be concluded that at a shear rate of 50/s the viscosity of the raw sample is around 8000

mPa.s, whereas the hydrolysed sample is only 150 mPa.s.

In the novel and patented mixing-separation step of the TurboTec® process, indicated as

Mobius-mixer, the above observations on viscosity in relation to temperature are

effectively translated into the novel process design. The cold raw sludge (+ 20°C) is

mixed with partially cooled hydrolysed sludge (105°C). In this way the raw sludge is very

efficiently heated to approximately 65°C. The specific characteristics of the two sludges

do, nonetheless, remain, allowing them to be separated again in a simple dynamic

separation process. The hydrolysed fluid sludge (thin fraction) is diverted to the

anaerobic digestion process, while the thick fraction is sent to the TurboTec® hydrolysis

reactor. Due to this initial temperature increase, the viscosity of the thick fraction sludge is

now such that a tube heat exchanger can be used effectively to raise the temperature

further.

The viscosity of the thin fraction and the thick fraction are shown in figure 3, where the

thick fraction contains the flocs of the raw sample along with any floc-like material in the

hydrolysed material. The thin fraction will contain all of the actually hydrolysed material,

either from the raw sample or from the hydrolysed material.

0

5

10

15

20

25

30

0 25 50 75 100 125

Vis

co

sit

y (

Pa.s

)

Shear rate (s-1)

raw sample

thick fraction

thin fraction

hydrolysed

Figure 3: Viscosity as function of share rate of different sludge samples.





This principle enables a more efficient heat recovery, while at the same time eliminating

the operational problems of the heat-exchangers.

Comparison of thin fraction with hydrolysed sludge

In order to verify that the Mobius mixing and separation does not deteriorate the effect

on the digestion, samples were compared in batch digestion tests. The graph below

shows the combined results, data are an average of two trials in duplo.

0

50

100

150

200

250

300

350

400

450

0 5 10 15 20 25

Bio

gas

pro

du

ctio

n (

l/kg

su

bst

rate

VS)

Residence time (days)

Hydrolysed with Mobius Mixer

Thin fraction

Hydrolysed without Mobius Mixer

Figure 4: Batch digestion test of various hydrolysed sludge fractions.

The sample of the hydrolysed sludge was taken after the initial cooling, but before the

Mobius-mixing with raw sludge. The “thin” fraction was taken from the stream to the

digester, after the Mobius mixing-separation.

The results in Figure 4, indicate that the application of the hydrolysis itself is improved by

the Mobius mixer. The explanation for this could be that material which is difficult to

hydrolyses will not pass the separation and will pass through the hydrolysis reactor again.

These results have been confirmed in numerous additional similar tests on samples from

the full scale reactor in Venlo and lab scale hydrolysis tests with different sludges.

Effect of hydrolysis temperature

Digestion tests have been done on lab-scale to determine the optimal hydrolysis

temperature. Samples from the plant in Venlo were hydrolysed at three different

temperatures 120, 140 and 160 °C and the anaerobic digestion was tested. The results

are presented in figure 5.

With respect to biogas production, the differences between the temperatures are small,

but an hydrolysis temperature of 140 °C seems optimal and was chosen as the default

temperature in the TurboTec®. The continuous process can be operated at a higher

temperatures with just a limited increase in heat demand due to the optimal heat

recovery. Higher temperatures however do not result in substantially higher biogas

productions. Limiting the temperature to 140 °C, has a positive effect on limitating or

avoiding the production of residual COD. Increasing the temperature beyond 140 °C





might still have a certain positive effect on the dewatering characteristics, but at the

expense of residual COD. (Hii et al, 2013)

150

200

250

300

350

400

450

500

0 5 10 15 20 25

Bio

gasp

rod

uct

ion

(l/

kg s

ub

stra

te V

S)

Residence time (days)

120 °C

140°C

160°C

Figure 5: Batch digestion test of hydrolysed sludge at different temperatures.

Process flow diagram of the TurboTec® process

The Mobius mixing-separation unit as part of the TurboTec® flow-scheme is presented

below in figure 6.

Figure 6: Set-up of the Venlo full-scale TurboTec® plant.





Results from the full-scale plant at WWTP Venlo

Plant description

WWTP Venlo is operated by the Waterboard Limburg and the capacity is 300.000 PE (@

150 kg COD/PE). The activated sludge plant is ultra-low loaded and makes use of

biological phosphate and nitrogen removal. The plant is operated without a primary

settler, so no primary sludge is produced. The total sludge production (WAS) equals 5400

ton TS/y. In addition to this flow, 1600 t TS/y of external sludge are processed at the plant.

This consists of 800 t TSS/y WAS from WWTP Gennep and 800 tTS/y digested sludge from

WWTP Venray.

The construction of the TurboTec® plant at WWTP Venlo was part of the renovation of the

sludge line. This included the construction of two digesters (2300 m3 each), application of

mechanical thickening and replacement of the existing centrifuges. The TurboTec® plant

was designed for a nominal capacity of 19.2 t TS/d (134 t TS/w) and a maximum

capacity of 26 t TS/d (182 T TS/w).

The inclusion of the Mobius mixing into the TurboTec process took place in march 2014.

Since then, the plant has been in continuous operation without any unplanned down

time.

In figure 7 the weekly throughput of the TurboTec® plant in combination with the specific

biogas production in Nm3/t VS input has been presented. Since the restart of the plant

the throughput of the plant was first steadily increased to a maximum of approximately

200 t TS/week. This was 10 % above the maximum design capacity, which is indicated by

the horizontal line in figure 7. This higher lading was caused by a peak demand in the

sludge treatment line, but had no adverse effects in the performance of the digester or

the TurboTec® plant. The experiences so far illustrate a stable and flexible operation.

0

50

100

150

200

250

300

350

400

450

500

13 18 23 28 33 38

Turbotec throughput and biogasproduction

Throughput t TS/week

Spec. Biogasproduciion, Nm3/ton VS in)

Figure 7: Production features of TurboTec plant at Venlo WWTP since restart.





Volatile Suspended-degradation

The results in figure 7 shows that the specific biogas production has been approximately

350 Nm3 / t VSinput during the last 8 weeks. Considering the character of the sludge

treated, with a COD-content of 1,5 kg COD/kg VS, and a methane content of 61 % of

the biogas, a complete conversion of the VS content would result in 850 Nm3 biogas.

Based on these data the biogas production can be related to a degradation efficiency

of the VS input of 41%.

While analysing the results of the Venlo plant in figure 7, the following should be kept in

mind:

11% of the VS input consists of digested sludge, upon hydrolysis this will give a

certain contribution to the degradation, but much lower than the original

secondary sludge. In our experience the degradation is around 50% of that of

raw WAS; Correcting for the amount of digested sludge, leads to a degradation

efficiency of approximately 43 % for the hydrolysed sludge.

No primary sludge is being digested, the input of the digester consists only of

hydrolysed WAS and hydrolysed digested sludge;

The results of the Venlo plant are in line with data from a recent evaluation into the

effect of thermal hydrolysis for WAS only. ( Camacho.P, et al, 2013)

Energy balance.

Figure 8 presents an energy-balance (enthalpy) for a typical mode of operation of the

Venlo plant. This includes a feed flow to the TurboTec plant of 8,1 m3/h at 11% TS content

or 890 kg/h TS (21,4 t TS/d).

Figure 8 clearly shows the extent of heat recovery that takes place within the TurboTec

plant. The nett input of heat required is 510 kW, which is supplemented by 580 kW heat

recovery by the heat exchangers and 760 kW of the pre-heated thick fraction. This

means that the total heat demand is supplied for 70 % by heat recovery and for 30 % by

steam input.

The heat content of the thin fraction at 56 °C is more than sufficient to provide the heat

demand of the digester, so the major part of this heat is utilised.

The heat demand of 510 kW, is provided as steam and equals around 660 kg/h of steam.

This means that the specific heat demand of the TurboTec® process under these

operating conditions is 745 kg/t DS input. This limited steam demand is one of the major

benefits of the TurboTec® process.

The steam used in the TurboTec® process at Venlo WWTP to reach the desired hydrolysis

temperature of 140 °C is generated in two different ways.:

by means of steam generation in a flue gas boiler fed by the cogeneration off-

gases;

by direct combustion of biogas in a steam boiler.

Because only WAS and digested WAS is being treated in Venlo the steam production

from the flue gas boiler is not sufficient to meet the overall steam demand.





MobiusMix-Separator

Heat exchanger

Heat exchanger

Cooled Hydrolysate1280 kW,97 °C, 11,3 m3/h

580 kWHeat recovery

Thick fraction760 kW61,5 °C10,6 m3/h

Thin fraction700 kW55,6 °C10,8 m3/h

Preheated Sludge1340 kW108 °C10,6 m3/h

TurboTec Reactor

Reactor discharge1850 kW140 °C11,3 m3/h

Steam510 kW180 °C0,7 m3/h

Feed190 kW20 °C8,1 m3/h

Figure 8: Energy flow diagram of TurboTec® at Venlo.

Figure 9 provides an overview of the way that the steam demand is met and the biogas

is being utilised.

Electricity

305 kW

Loss

Radiation fluegas

Ventilation 215 kW

loss

65 kW

Cogen-Units

1020 kW

Biogas Yield1330 kW

Biogas to Cogen1020 kW

Heat in engine cooling 205 kW

Heat in fluegases 445 kW FGB

445 kW

TurbotTec510 kW

ESG 320 kW

Biogas to ESG320 kW

Steam fromfluegas 230 kW

Steam formbiogas280 kW

Loss ESG40 kW

Figure 9: Biogas utilisation Venlo WWTP, treating only WAS, load 8,1 m3/h @11% TS.





From figure 9 it can be seen that in the Venlo case the steam demand of the TurboTec®

process is covered more or less equally by the heat form the Cogen-units and by direct

combustion of biogas. This means that around 25% of the biogas production has to be

used directly for steam production.

In a situation where also primary sludge is digested more biogas is available for the

Cogen –Units. Considering the higher specific biogas production from primary sludge,

the heat demand of the TurboTec® process can be met completely by the flue gas

boiler of the Cogen-units if 30% or more of the TS amount for digestion consists of primary

sludge.

Effect on dewatering

In addition to the improvement of the degradation of organic matter in WAS, the

TurboTec® process results in a significant improvement of the dewatering characteristics.

In figure 10, the development of the TS-content of the sludge cake since the restart of the

plant in April 2014. Results are shown for both centrifuges separately. Until the beginning

of May, Centrifuge 1 has still been applied to directly dewater the surplus WAS, while

centrifuge 2 was handling the digested sludge. The latter results in a TS content of the

sludge cake of 22% on average. By the beginning of May, the treatment capacity of the

digestion was sufficient to treat all of the sludge by thermal hydrolysis. Figure clearly

indicates the improvement of the resulting TS content. The lasts results are in the range of

29 – 30% TS content.

0

5

10

15

20

25

30

35

2-3-2014 21-4-2014 10-6-2014 30-7-2014 18-9-2014 7-11-2014

TS c

on

ten

t sl

ud

ge c

ake

(%

TS)

Date 2014

TS content sludge cake centrifuge 1

TS content sludge cake centrifuge 2

20 per. Zw. Gem. (TS content sludge cake centrifuge 1)

20 per. Zw. Gem. (TS content sludge cake centrifuge 2)

period of dewateringuntreated WASby centrifuge 1

Figure 10: Development of the TS-content of the sludge cake since the restart.





Summary of results from the Venlo plant

The practical results of the Venlo Plant can be summarised as follows:

stable operation of the c-THP plant and the digestion over a period of 30 weeks

without any unplanned downtime;

A high degree of flexibility with respect to the amount of sludge to be treated;

Improved VS-reduction for the WAS and digested sludge treated in the digester;

A steam demand of less than 800 kg/t TS input to the c-THP

The high degree of heat-recovery allows for a limited degree of pre-dewatering.

(11% TS). This reduces the requirements for electricity and flocculation agent

significantly compared to dewatering to 16 % TS or higher

Positive effects on dewatering resulting in a TS content of the sludge cake of 29 –

30% TS.

National and international Prospects

The construction of the second full-scale plant is nearing its completion. Final tests before

taking the plant into operation are expected to be performed before the end of the

year 2014.

In addition to the construction of the c-THP plant, the project at WWTP Apeldoorn

involves the recovery of phosphate in the sludge line. The combination will improve the

performance and the stability of the substantially, while at the same time existing

problems with struvite formation in pipelines will be solved. Figure 11 gives an impression

of the set-up of the c-THP plant that is being realised at WWTP Apeldoorn. This plant will

treat WAS form a number of WWTP’s and has a design capacity of 13.000 t TS/an.

Figure 11: Impression of the TurboTec® plant at WWTP Apeldoorn with hydrolysis

reactor on the right and mixing-separation unit in between the heat

exchangers.





Operational advantages of the TurboTec® c-THP application

Batch wise operated hydrolysis systems typically operate with a TS content of around

16%, while the TurboTec® applies TS contents of 10 – 12%. This difference allows for the

application of less advanced ways for thickening of the sludge. While batch systems

generally apply centrifuges, TurboTec® can make use of belt thickeners. Both systems

have their specific demands for polymer (PE) and electricity in thickening and steam

demand for the hydrolysis. The typical values of these demands are presented in table 1

and in figure 12.

Figure 12 shows that batch systems result in an increased demand in operational effort

for electricity, polymer consumption and steam. Even for steam demand, the increased

TS content and reduced sludge volumes for batch systems still results in less favourable

conditions compared to the typical conditions of the TurboTec® process. In table 2 these

consumables have been translated to operational costs, giving a significant advantage

of around 26 €/ton TS treated to the c-THP process. (Belshaw etal, 2013)(Panter etal,

2013)(Pook et al 2013)

Table 1: Specific consumables of batch systems vs. TurboTec®

Parameter Batch system TurboTec®

system

Unit

Pre-thickening

TS-content after thickening

16%

11%

Polymer demand

Electricity demand

8

75

4

15

kg PE/ton TS

kWh/ton TS

THP

Electricity demand

39

52

kWh/ton TS

Steam demand 950 800 Kg/ton TS





0

10

20

30

40

50

60

70

80

0

200

400

600

800

1000

1200

1400

1600

0% 2% 4% 6% 8% 10% 12% 14% 16% 18%

PEd

em

and

kg/

ton

TS

and

E-d

em

and

in k

Wh

/to

n T

S

Ste

amv

de

man

d k

g/to

n T

S

TS content sludge

steam (kg/ton TS)

p.e (kg/ton TS)

E (kWh/ton TS)Continuous systems Batch systems

TurboTec

Figure 12: Comparison of consumables of batch and continuous THP systems

Table 2: Specific Operational Costs batch systems vs. TurboTec®

Operational costs Batch system TurboTec®

system

Unit

Electricity 10.3 6.0 €/ton TS

Polymer

Steam

Total

37.0

19.0

66.3

18.5

16.0

40.5

€/ton TS

€/ton TS

€/ton TS

Difference 25.8 €/ton TS

Unit prices: electricity 0.09 €/kWh, PE 1,94 €/kg PE 42% active), steam 20.0 €/ton

Conclusions

The performance of the TurboTec® plant at Venlo WWTP clearly demonstrates the

maturity of the concept and has resulted in stable operation with a high degree of

flexibility and low operational costs.

The high degree of heat recovery allows for less advanced technology for the pre-

thickening of the sludge, while at the same time a low demand for steam is maintained.

Considering these experiences we would like to stress the importance of taking an

overall approach when evaluating the feasibility of applying THP for future projects

without limiting the choice of technologies.





References

Belshaw, D., R.M. Eddington, M. Jolly, (2013) Commissioning of United Utilities thermal

hydrolysis digestion plant at Davyhulme waste water treatment works, presentation at

18th Eur.Biosolids & Org.Res. Conf., November 2013 Manchester.

Camacho, P. etal., 2008, Combined experiences of thermal hydrolysis and anaerobic

digestion – latest thinking on thermal hydrolysis of secondary sludge only for optimum

dewatering and digestion, WEFTEC 2008, Session 21 through Session 30, pp. 1964-1978(15).

Estiaghii, N, Hydrothermal processing of sludge- a review, presentation at Chemeca

2013, Challenging tomorrow, paper 28282, Brisbane.

Panter, K., H. Holte, P. Waleley, (2013) Challenges of developing small thermal hydrolysis

and digestion projects, presentation at 18th Eur.Biosolids & Org.Res. Conf., November

2013 Manchester.

Pook M., etal, (2013) Exploring the upper limits of THP at Chertsey STW, presentation at

18th Eur.Biosolids & Org.Res. Conf., November 2013 Manchester.

STOWA, (2012) Thermische slibontsluiting, report 2012-25.


Documents

Full scale experiences with TurboTec continuous thermal ...€¦ · continuous TurboTec® THP system is introduced, this process offers the opportunity of lower investment and substantially