- Email: [email protected]
New technology of mechanical treatment of dredged material from Hamburg Harbour
~
Pergamon
Wat. Sci Tech. Vol. 37. No. 6-7. pp. 337-343. 1998. C 1998 1AWQ. Published by Elsevier Science Ltd Printed in Great Britain.
PIT: S0273-1223(98)00216-9
0273-1223/98 S19'00 + 0-00
NEW TECHNOLOGY OF MECHANICAL TREATMENT OF DREDGED MATERIAL FROM HAMBURG HARBOUR Heinz D. Detzner, Wolfgang Schramm, Ulrich Doring and Wolfgang Bode Freie und Hansestadt Hamburg, Wirtscha/tsbehOrde, Strom- und Hafenbau, Da/mannstrasse /-3, D 20457 Hamburg, Germany
ABSTRACT Harbours and water ways can only fulfil their commercial task if there is always sufficient water depth for navigation. Environmental problems have started to influence dredging methods in recent decades. As a logical consequence of a policy giving high priority to environmental protection. Hamburg built the ME1HA plant (Mechanical Treatment of Harbour Sediments). METHA produces a clean sand product (grain size> 63 11m) which is reused and a contaminated silt fraction (grain size < 150 1J.rn) which is disposed presently. Previous investigations showed that the content of heavy metals and organic contaminants are primarily governed by the grain size. In 1995 Strom- und Hafenbau started a new investigation to produce a further fraction from the METHA silt which can be reused. The result of laboratory- and pilot-scale research showed the possibility of a further separation at 20 IJ.rn grain size. The best result was reached through a two-step separation made by hydrocyclons and spirals. The produced fraction (20-150 1J.rn) is mainly quartz material with a low level of contamination. In February 1996 Strom- und Hafenbau decided to built a test plant in a technical scale. The capacity of the test-plant is 50 tIh based on dry substance The technical concept is integrated into the METIIA concept. All aspects of technical feasibility. economy. environment and product reuse will be investigated in the test plant. The results of the early test phase will be presented. @ 1998 IAWQ. Published by Elsevier Science Ltd
KEYWORDS Dredged material; environmental protection; Hamburg Harbour; METHA; reuse; separation; treatment. INTRODUCTION Every year Hamburg produces on average approximately 2 million m3 dredged material by maintenance dredging. At the same time dredged sediments are carrier of toxins for many natural and anthropogenic materials brought into the water. This fact and the knowledge that at least up to the political turning point in Germany the river Elbe belongs to the most seriously burdened rivers of middle and Western Europe. led to development and conversion of a new dredged material concept in the 80s in Hamburg (Netzband. 1994) with considerable financial costs. The concept which includes dredged material treatment. sewage treatment and disposal in silt hills will be good for a medium-term period in order to exhibit corresponding possible developments and adaptations. Such an adaptation can be. for example. a procedural technical alternative for disposal of dredged material if this is technically well enough developed and sufficient for ecological and economical requests. 337
338
H. D. DETZNER et al.
Based on the knowledge that the contaminated materials are associated preferably with fine grain fraction « 20 J.lm), colleagues of METHA developed a procedure which can separate by physical separating technologies the available silt fraction into a fraction that is lower in toxins, utilizable fine sand fraction (20 J.Lrn-150 J.lm) and a toxic fine silt fraction « 20 J.lm). Typical toxic material distribution of the Hamburg dredged material was presented already earlier in detail (for example, Kroning, 1990). Previous results are also confirmed by data shown in Table I as toxic material loads of the available silt material (measured in the cumulative sample and < 20 J.lm fraction). The higher concentration is shown clearly with the various toxins in the fraction < 20 J.lm. These findings confirmed the possible use of the silt fraction as output material for further treatment. Table 1. Contamination levels of METHA - silt in 3/1993 - 3/1997 (cumulative sample and fraction < 20 J.lm, Solids) METHA- Silt cumulative sample Parameter Ignition loss [% d.m.] TOC[%d.m.] pH Arsenic [mg/kg dm.] Lead [mg/kg d.m.] Cadmium [mg/kg d.m.] Chromium [mg/kg d.m.] Copper [mg/kg dm.] Nickel [mg/kg dm.] Mercury [mg/kg dm.] Zinc [mg/kg d.m.] Cyanide [mg/kg dm.] EOX [mg/kg dm.] Hydrocarbons [mg/kg d.m.] PAH (EPA) [mg/kg dm.] PCB (6) [mg/kg d.m.]
Range
Median
6.7 - 12.5 2.2 - 6.4 6.53 - 8.39
9.5 4.25 7.13
17 - 46 57 - 210 1.9 - 5.1 61 - 120 70·190 28 - 52 1.6 -7.0 370- 940
32 91 3.7 93 110 40.5 3.7 695
1.3·68 < I - 32 100 - 1200 < 0.8·38.5 <0.01 -0.09
3.9 <1 455 5.2 <0.01
Technical guidelines for mineral residues (LAGA, 1994) solids
Fraction < 20 f1m Range
Median
37 -90 130 - 370 3.6 - 9.1 140- 200 140 - 290 67 - 110 4.7 - 12 1100-1700
53 160 6.5 160 190 82 7.1 1300
ZO
Zl.l
5.5 - 8 5.5 - 8 20 100 0.6 50 40 40 0.3 120
30 200 1 100 100 100 I 300
1 I 100 I 0.02
10
3
300 5 0.1
Z 1.2
Z2
5-9 50 300 3 200 3 500
150 1000 10 600 600 600 10 1500
30 10 500 15 0.5
100 15 1000 20 1
200 200
dm. = dry material EOX extractable organic hologens
=
From the beginning the goal of the development was the production of material which could be conveniently utilized regarding its quality and content of the toxins. The efforts of METHA employees were supported by the fact that majority of the METHA silt fraction is greater than 20 J.lm. Therefore sufficient exploitation of useful material can be expected (comp. Figure I). Almost exactly 4 years after the start of METHA as the world wide first large plant for the separation of dredged material and with the official start of operations of the large test plant for 20 J.lm separation in April 1997, the treatment of Hamburger dredged material gets a new quality. With the same quantity and quality of dredged material, less silt will be used on the hills by using the fine sand separation. This leads to better utilization of the Hamburg hill capacity. It is the goal to use the fine sand produced by the separation as building material or building material additive. At present, the use of the fine sand in various areas of the construction industry is under examination. The permission for use as additive material in road construction is already under consideration. The new technology of find sand separation is described in more detail below. Perspectives with the goal to use more sediments and their fractions in the future are also discussed.
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Figure I. Grain size range ofMETHA silt in 3/1993 - 3/1997.
OPERATION PRINCIPLE OF FINE SAND PLANT The fine sand separation represents no basic change of the available METRA-procedure (Detzner et ai., 1993; Detzner, 1995), but is rather an extension of the process. The use of the additional separate step into the available process is presented in Figure 2. First of all, the fine sand separation will be realized for 50% of METHA throughput, i.e. 60 td.m.' The essential procedures and technical components of this extension are: Hydrocyclones - separation at 20 J.1m Spirals - separation of fine organic materials Vacuum belt filter - dewatering of find sand product The silt suspension of hydrocyclones and upstream sorter overflow of the available METHA is the input material of the fine sand separation. Organic components are first separated from the suspension by a wing sieve with a mesh of 1.5 mm. The sieving of the rough organic matter serves to protect the following technical components from plugging up, as well as the improvement of the product quality. The sieve residue (rough matter) is transported by a belt. The sieve output arrives into the pump cavity of the cyclone pump. The separation of the silt suspension results in two parallel streams. These consist of a hydrocyclone group with 32 individual cyclones (d 100 mm) and later spiral concentrators. The silt suspension is given to the cyclone group and is separated there into a fine silt fraction « 20 IJ.m) and into a fine sand group (20-150 IJ.m). The fine sand fraction comes up at the cyclone underflow and is fed to the next process step, the spiral concentrators. The spiral concentrators have the task of set free the fine sand extensively from remaining organic components as well as coal, wood and plant remainders because these are toxic material carriers and will negatively influence the product quality. The further cleaned fine sand is dewatered by a vacuum belt filter and brought to its stock via a belt.
=
H. D. DETZNER et al.
340
Dredged Material
'rom ItonIge !III1n dh jn4CNelIlng
Fine SInd I Fine Silt
.e
separation (20 11m)
DewaterIng
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_
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COMtructIon IIlIlIrlII 01111 hi..
Hamburg Figure 2. Simplified flow sheet of METHA fine sand process.
The upperflow of the cyclones and the separated, organically enriched fraction of the spiral concentrators are combined and form the fine silt fraction. This suspension is brought to the available METHA dewatering process, Le. the suspension is introduced into the available thickeners and subsequently drained with the existing filter press systems. The success of the installed 20 11m separation indicated by the range of grain size of the fine sand and fine silt product and the concentration of the contamination in the fine sand product is presented in Figure 3 and Table 2, respectively. The heavy metal load of the METHA fine silt fraction is based on first analyses on an order of magnitude as well as in the METHA-silt in the fraction < 20 11m that was analysed earlier (Table 1). UTILIZATION OF THE METHA-PRODUCTS Uniform guidelines do not exist at present for regulation of suitability of dredged material as secondary raw material, building material or building material additive in the Federal Republic of Germany. Therefore the criteria of the state work group for waste removal ,demands on the organic utilization of mineral remainder materials / waste" [Anforderungen an die stoffliche Verwertung von mineralischen Reststoffen / Abflillen] (LAGA, 1994) are frequently used. According to that document. utilization is defined as the direct use of secondary materials but also the use. e.g. as building material additive or for the production of building materials. For assessment purposes, a classification system is used, which is based on the origin, state and use according to location prerequisites. The assessment purposes also take into consideration environmentally compatible utilization under consideration of risk potential. One distinguishes at the same time between the so-called integration classes (coordination values) "unlimited integration 'ZlJ". "restricted use dependent open integration Zl" and "restricted use dependent integration with defined technical back-up measures Z2".
341
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10
1
I
I
100
I 1000
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Figure 3. Grain size range of fine sand and fine silt products in test phase springtime 1997.
Table 2. Contamination levels ofMETHA fine sand during the early testphase in spring 1997 (solid and elutriate) Technical guidelines for mineral residues (LAGA, 1994)
METHA - Fine sand 20 - 150 Illll Elutriate Ij
Solids
Parameter Ignition loss [% d.m.] pH Arsenic [mglkg d.m.) Lead [mg/kg d.m.] Cadmium [mglkg d.m.] Chromium [mglkg d.m.] Copper [mglkg dm.] Nickel [mglkg dm.] Mercury [ma/kg d.m.] Zinc [mglkg d.m.] Cyanide [ma/kg dm.] EOX [mglkg d.m.] Hydrocarbons [mgIkg d.m.] PAH (EPA) [mglkg d.m.] PCB (6) [mglkg d.m.]
Solids
Zl.l
Elutriate Ij
ZO
Zl.l
Range
Median
Range
Median
<2 7.2 -7.95
7.77
7.47 -7.94
7.82
3.8 - 6.9 11-20 0.32-0.80 7.8 - 35 31- 88 7.3 - 15 0.23 -0.57 85 - 140
6.1 17 0.53 25 48 12 0.47 130
3 - 5.4 <2 <0.3 - 0.4 <2 5 - 13 <5 -12 <0.2 <10-20
4.3 <2 <0.3 <2 8 7 <0.2 10
20 100 0.6 50 40 40 0.3 120
30 200 1 100 100 100 1 300
10 20 2 15 50 40 0.2 100
2 30 SO SO 0.2 100
<0.05 -0.21 < 1- 3 20 - ISO <0.8 - 3.6 0.01- 0.14
0.14 <1 66 0.9 0.04
<5
<5
1 1 100 1 0.02
10 3 300 5 0.1
<10
10
ZO
5.5 - 8 5.5 - 8 6.5 - 9 6.5 - 9 10
40
dm.• dry material EOX • extractable Ol'lanic h010gens ") Elutriate in IlI!l
For the current products of METRA, sand and silt, clear utilization guidelines have been developed during the last years. These are economically and ecologically justified. Therefore the sand fraction of METRA is used at different building projects directly as building sand. The sand can be used without restrictions
342
H. D. DETZNER et al.
regarding to the ecological criteria. A decisive factor for the actual use is essentially the construction criteria. Examples for such utilization of the sand fraction are the integration into drainage layer and edge support sections of the hill construction. METHA silt is inserted at present into the hills. The basics of the technology were described in detail by Netzband (1994). Alternative investigations into the utilization of silt as backfilling material of caverns was addressed at the International Conference on Contaminated Sediments, Rotterdam 1997 by Glindemann (1997) and therefore will not be described any further. With the technology described above for further separation at 20 Ilm a product fraction is available now which can find a variety of utilization. These will be examined in the near future in more detail. According to the criteria of the LAGA (1994), METHA fine sand can be categorized with the help of the toxin concentration shown in Table 2. It represents the category "restricted use dependent integration" whereby most values would allow even for a classification into the category "unlimited utilization". Therefore the prerequisites are given for utilization of fine sand. The possibilities in the cement industry, chalk-sand stone industry or also concrete industry must be mentioned, since METHA fine sand can be inserted as raw material alternative for pulverized sand. Contacts with the industries were already established, and utilization trials and investigations will be carried out in the course of the business of the large test plant. Utilization in road construction, for example, in asphalt production is possible. Required investigations for certification of fine sand to be permitted as building material are already under way. Altogether the goal of all efforts appears to create a high demand market product after termination of the investigation phase. The fine silt fraction out of the 20 Ilm separation is supposed to be utilized primarily in hill building. In the course of the now running test plant, also the yet unanswered questions are supposed to be examined. For example the behaviour of fine silt under integration conditions in a hill is not known. Also the soil mechanical installation parameters will be examined. Further possibilities for utilization, both for the conventional silt and fine silt is the brick production. The Hamburg company HZG-Hanseaten-Stein Ziegelei GmbH has succeeded in developing a production methodology that makes it possible to manufacture high-value ceramic building materials such as wall bricks, building bricks, cobblestones, using dredged material such as the Elbe River sediments. The research and development reached a level in 1993, which appears to realize these ideas in the framework of a larger plant and for industrial production. After many years of planing, certification, and building, and with an investment of almost 20 million OM for production and environmental protection arrangements, the HZG, a medium size Hamburg company, built a large technical demonstration site for brick production. The site is the only one of its kind world wide, also regarding the plant safety and waste gas cleaning technology in the construction material industry. The production capacity of the brick plant in Hamburg-Neuenfelde is approx. 5 million bricks per year.
In Figure 4 the basic flow of the technology is shown. Using dredged material instead of natural clay minerals in the production of bricks places especially high demands on the preparation, shaping and bum process of the input materials. In addition, it requires, from environmental protection aspects, the highest possible cleaning and supervision of emissions that may occur during the production process. Because these criteria are given with the Hamburger technology, a contract was set up accordingly at the end of 1995 between the HZG and Strom- und Hafenbau. The contract agrees to provide the METHA silt delivery for the 3-4 year demonstration period of up to 30.000 t METHA silt. With the current technical large scale investigations at the demonstration brick production in Hamburg-Neuenfelde, the required framework parameters are supposed to be determined. The aim is to reach an economically and ecologically wise technology of the dredged material utilization for the future.
New technology of mechanical treatment
343
I1IlurII ferroglnoul IIdlmlllll clay . . . . METHA lilt
Figure 4. Simplified flow sheet of METHA fine sand process
REFERENCES Detzner, H. D., Kitschen, L. and Weimerskirch, W. (1993). METHA - the first large-scale plant for treatment of harbour sediments. Aufbereitungstechnik/ Mineral Processing, 34(5), 235-242. Detzner, H. D. (1995). The Hamburg project METHA: large-scale separation, dewatering and reuse of polluted sediments. European Water Pollution Control, 5(5), 38-42. Glindemann, H. (1997). The development of Hamburgian concepts to handle dredged material. International Conference on Contaminated Sediments, September 7 - I I, 1997, Rotterdam Kroning, H. (1990). Separation and dewatering of fine-grained organic-mineral dredgings. Aufbereitungstechnik / Mineral Processing, 31(4), 205-214. LAGA - Uinderarbeitsgemeinschaft Abfall (1994). Anforderungen an die stoffliche Verwenung von mineralischen Reststoffen/Abfiillen - Technische Regeln - 20/1, Erich Schmidt Verlag, Berlin. Netzband, A. (1994). Dredged material management in the port of Hamburg. European Water Pollution Control, 4(6), 47-53.
Pergamon
Wat. Sci Tech. Vol. 37. No. 6-7. pp. 337-343. 1998. C 1998 1AWQ. Published by Elsevier Science Ltd Printed in Great Britain.
PIT: S0273-1223(98)00216-9
0273-1223/98 S19'00 + 0-00
NEW TECHNOLOGY OF MECHANICAL TREATMENT OF DREDGED MATERIAL FROM HAMBURG HARBOUR Heinz D. Detzner, Wolfgang Schramm, Ulrich Doring and Wolfgang Bode Freie und Hansestadt Hamburg, Wirtscha/tsbehOrde, Strom- und Hafenbau, Da/mannstrasse /-3, D 20457 Hamburg, Germany
ABSTRACT Harbours and water ways can only fulfil their commercial task if there is always sufficient water depth for navigation. Environmental problems have started to influence dredging methods in recent decades. As a logical consequence of a policy giving high priority to environmental protection. Hamburg built the ME1HA plant (Mechanical Treatment of Harbour Sediments). METHA produces a clean sand product (grain size> 63 11m) which is reused and a contaminated silt fraction (grain size < 150 1J.rn) which is disposed presently. Previous investigations showed that the content of heavy metals and organic contaminants are primarily governed by the grain size. In 1995 Strom- und Hafenbau started a new investigation to produce a further fraction from the METHA silt which can be reused. The result of laboratory- and pilot-scale research showed the possibility of a further separation at 20 IJ.rn grain size. The best result was reached through a two-step separation made by hydrocyclons and spirals. The produced fraction (20-150 1J.rn) is mainly quartz material with a low level of contamination. In February 1996 Strom- und Hafenbau decided to built a test plant in a technical scale. The capacity of the test-plant is 50 tIh based on dry substance The technical concept is integrated into the METIIA concept. All aspects of technical feasibility. economy. environment and product reuse will be investigated in the test plant. The results of the early test phase will be presented. @ 1998 IAWQ. Published by Elsevier Science Ltd
KEYWORDS Dredged material; environmental protection; Hamburg Harbour; METHA; reuse; separation; treatment. INTRODUCTION Every year Hamburg produces on average approximately 2 million m3 dredged material by maintenance dredging. At the same time dredged sediments are carrier of toxins for many natural and anthropogenic materials brought into the water. This fact and the knowledge that at least up to the political turning point in Germany the river Elbe belongs to the most seriously burdened rivers of middle and Western Europe. led to development and conversion of a new dredged material concept in the 80s in Hamburg (Netzband. 1994) with considerable financial costs. The concept which includes dredged material treatment. sewage treatment and disposal in silt hills will be good for a medium-term period in order to exhibit corresponding possible developments and adaptations. Such an adaptation can be. for example. a procedural technical alternative for disposal of dredged material if this is technically well enough developed and sufficient for ecological and economical requests. 337
338
H. D. DETZNER et al.
Based on the knowledge that the contaminated materials are associated preferably with fine grain fraction « 20 J.lm), colleagues of METHA developed a procedure which can separate by physical separating technologies the available silt fraction into a fraction that is lower in toxins, utilizable fine sand fraction (20 J.Lrn-150 J.lm) and a toxic fine silt fraction « 20 J.lm). Typical toxic material distribution of the Hamburg dredged material was presented already earlier in detail (for example, Kroning, 1990). Previous results are also confirmed by data shown in Table I as toxic material loads of the available silt material (measured in the cumulative sample and < 20 J.lm fraction). The higher concentration is shown clearly with the various toxins in the fraction < 20 J.lm. These findings confirmed the possible use of the silt fraction as output material for further treatment. Table 1. Contamination levels of METHA - silt in 3/1993 - 3/1997 (cumulative sample and fraction < 20 J.lm, Solids) METHA- Silt cumulative sample Parameter Ignition loss [% d.m.] TOC[%d.m.] pH Arsenic [mg/kg dm.] Lead [mg/kg d.m.] Cadmium [mg/kg d.m.] Chromium [mg/kg d.m.] Copper [mg/kg dm.] Nickel [mg/kg dm.] Mercury [mg/kg dm.] Zinc [mg/kg d.m.] Cyanide [mg/kg dm.] EOX [mg/kg dm.] Hydrocarbons [mg/kg d.m.] PAH (EPA) [mg/kg dm.] PCB (6) [mg/kg d.m.]
Range
Median
6.7 - 12.5 2.2 - 6.4 6.53 - 8.39
9.5 4.25 7.13
17 - 46 57 - 210 1.9 - 5.1 61 - 120 70·190 28 - 52 1.6 -7.0 370- 940
32 91 3.7 93 110 40.5 3.7 695
1.3·68 < I - 32 100 - 1200 < 0.8·38.5 <0.01 -0.09
3.9 <1 455 5.2 <0.01
Technical guidelines for mineral residues (LAGA, 1994) solids
Fraction < 20 f1m Range
Median
37 -90 130 - 370 3.6 - 9.1 140- 200 140 - 290 67 - 110 4.7 - 12 1100-1700
53 160 6.5 160 190 82 7.1 1300
ZO
Zl.l
5.5 - 8 5.5 - 8 20 100 0.6 50 40 40 0.3 120
30 200 1 100 100 100 I 300
1 I 100 I 0.02
10
3
300 5 0.1
Z 1.2
Z2
5-9 50 300 3 200 3 500
150 1000 10 600 600 600 10 1500
30 10 500 15 0.5
100 15 1000 20 1
200 200
dm. = dry material EOX extractable organic hologens
=
From the beginning the goal of the development was the production of material which could be conveniently utilized regarding its quality and content of the toxins. The efforts of METHA employees were supported by the fact that majority of the METHA silt fraction is greater than 20 J.lm. Therefore sufficient exploitation of useful material can be expected (comp. Figure I). Almost exactly 4 years after the start of METHA as the world wide first large plant for the separation of dredged material and with the official start of operations of the large test plant for 20 J.lm separation in April 1997, the treatment of Hamburger dredged material gets a new quality. With the same quantity and quality of dredged material, less silt will be used on the hills by using the fine sand separation. This leads to better utilization of the Hamburg hill capacity. It is the goal to use the fine sand produced by the separation as building material or building material additive. At present, the use of the fine sand in various areas of the construction industry is under examination. The permission for use as additive material in road construction is already under consideration. The new technology of find sand separation is described in more detail below. Perspectives with the goal to use more sediments and their fractions in the future are also discussed.
New technology of mechanical treatment
100
-Min
-Max
90
l
8
I
50
i
30
I
20
V 1/ / 1/ 1// ~I' V V /' ,/
80
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70
1:1
e
1/1'
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80
339
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.. ioo'
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o 1
10
grain size d lJ,ImJ
100
1000
Figure I. Grain size range ofMETHA silt in 3/1993 - 3/1997.
OPERATION PRINCIPLE OF FINE SAND PLANT The fine sand separation represents no basic change of the available METRA-procedure (Detzner et ai., 1993; Detzner, 1995), but is rather an extension of the process. The use of the additional separate step into the available process is presented in Figure 2. First of all, the fine sand separation will be realized for 50% of METHA throughput, i.e. 60 td.m.' The essential procedures and technical components of this extension are: Hydrocyclones - separation at 20 J.1m Spirals - separation of fine organic materials Vacuum belt filter - dewatering of find sand product The silt suspension of hydrocyclones and upstream sorter overflow of the available METHA is the input material of the fine sand separation. Organic components are first separated from the suspension by a wing sieve with a mesh of 1.5 mm. The sieving of the rough organic matter serves to protect the following technical components from plugging up, as well as the improvement of the product quality. The sieve residue (rough matter) is transported by a belt. The sieve output arrives into the pump cavity of the cyclone pump. The separation of the silt suspension results in two parallel streams. These consist of a hydrocyclone group with 32 individual cyclones (d 100 mm) and later spiral concentrators. The silt suspension is given to the cyclone group and is separated there into a fine silt fraction « 20 IJ.m) and into a fine sand group (20-150 IJ.m). The fine sand fraction comes up at the cyclone underflow and is fed to the next process step, the spiral concentrators. The spiral concentrators have the task of set free the fine sand extensively from remaining organic components as well as coal, wood and plant remainders because these are toxic material carriers and will negatively influence the product quality. The further cleaned fine sand is dewatered by a vacuum belt filter and brought to its stock via a belt.
=
H. D. DETZNER et al.
340
Dredged Material
'rom ItonIge !III1n dh jn4CNelIlng
Fine SInd I Fine Silt
.e
separation (20 11m)
DewaterIng
mechMaJ clIw*Inll ~
lhlcll8nlrl nhr
~\ _
SInd
.COIIIlIllClIon ......
_
Fine SInd
• COMtructIon IIlIlIrlII
Silt I Fine Silt
COMtructIon IIlIlIrlII 01111 hi..
Hamburg Figure 2. Simplified flow sheet of METHA fine sand process.
The upperflow of the cyclones and the separated, organically enriched fraction of the spiral concentrators are combined and form the fine silt fraction. This suspension is brought to the available METHA dewatering process, Le. the suspension is introduced into the available thickeners and subsequently drained with the existing filter press systems. The success of the installed 20 11m separation indicated by the range of grain size of the fine sand and fine silt product and the concentration of the contamination in the fine sand product is presented in Figure 3 and Table 2, respectively. The heavy metal load of the METHA fine silt fraction is based on first analyses on an order of magnitude as well as in the METHA-silt in the fraction < 20 11m that was analysed earlier (Table 1). UTILIZATION OF THE METHA-PRODUCTS Uniform guidelines do not exist at present for regulation of suitability of dredged material as secondary raw material, building material or building material additive in the Federal Republic of Germany. Therefore the criteria of the state work group for waste removal ,demands on the organic utilization of mineral remainder materials / waste" [Anforderungen an die stoffliche Verwertung von mineralischen Reststoffen / Abflillen] (LAGA, 1994) are frequently used. According to that document. utilization is defined as the direct use of secondary materials but also the use. e.g. as building material additive or for the production of building materials. For assessment purposes, a classification system is used, which is based on the origin, state and use according to location prerequisites. The assessment purposes also take into consideration environmentally compatible utilization under consideration of risk potential. One distinguishes at the same time between the so-called integration classes (coordination values) "unlimited integration 'ZlJ". "restricted use dependent open integration Zl" and "restricted use dependent integration with defined technical back-up measures Z2".
341
New technology of mechanical treatment
100
-MIN
90
eo
8
70
FIne
I: 5
II
.I,~I
-AlIlIrage
l
"//
~
-MAX
sIn A~
/J
f/
/I 7
40
I:
I
I) /
~
FIne Sand
I
I /
I.
10
I
V I
,,~ ~
'I
V
J
I
~ I
l..."..ooo"
o
1
10
1
I
I
100
I 1000
grain alze d [Jlml
Figure 3. Grain size range of fine sand and fine silt products in test phase springtime 1997.
Table 2. Contamination levels ofMETHA fine sand during the early testphase in spring 1997 (solid and elutriate) Technical guidelines for mineral residues (LAGA, 1994)
METHA - Fine sand 20 - 150 Illll Elutriate Ij
Solids
Parameter Ignition loss [% d.m.] pH Arsenic [mglkg d.m.) Lead [mg/kg d.m.] Cadmium [mglkg d.m.] Chromium [mglkg d.m.] Copper [mglkg dm.] Nickel [mglkg dm.] Mercury [ma/kg d.m.] Zinc [mglkg d.m.] Cyanide [ma/kg dm.] EOX [mglkg d.m.] Hydrocarbons [mgIkg d.m.] PAH (EPA) [mglkg d.m.] PCB (6) [mglkg d.m.]
Solids
Zl.l
Elutriate Ij
ZO
Zl.l
Range
Median
Range
Median
<2 7.2 -7.95
7.77
7.47 -7.94
7.82
3.8 - 6.9 11-20 0.32-0.80 7.8 - 35 31- 88 7.3 - 15 0.23 -0.57 85 - 140
6.1 17 0.53 25 48 12 0.47 130
3 - 5.4 <2 <0.3 - 0.4 <2 5 - 13 <5 -12 <0.2 <10-20
4.3 <2 <0.3 <2 8 7 <0.2 10
20 100 0.6 50 40 40 0.3 120
30 200 1 100 100 100 1 300
10 20 2 15 50 40 0.2 100
2 30 SO SO 0.2 100
<0.05 -0.21 < 1- 3 20 - ISO <0.8 - 3.6 0.01- 0.14
0.14 <1 66 0.9 0.04
<5
<5
1 1 100 1 0.02
10 3 300 5 0.1
<10
10
ZO
5.5 - 8 5.5 - 8 6.5 - 9 6.5 - 9 10
40
dm.• dry material EOX • extractable Ol'lanic h010gens ") Elutriate in IlI!l
For the current products of METRA, sand and silt, clear utilization guidelines have been developed during the last years. These are economically and ecologically justified. Therefore the sand fraction of METRA is used at different building projects directly as building sand. The sand can be used without restrictions
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regarding to the ecological criteria. A decisive factor for the actual use is essentially the construction criteria. Examples for such utilization of the sand fraction are the integration into drainage layer and edge support sections of the hill construction. METHA silt is inserted at present into the hills. The basics of the technology were described in detail by Netzband (1994). Alternative investigations into the utilization of silt as backfilling material of caverns was addressed at the International Conference on Contaminated Sediments, Rotterdam 1997 by Glindemann (1997) and therefore will not be described any further. With the technology described above for further separation at 20 Ilm a product fraction is available now which can find a variety of utilization. These will be examined in the near future in more detail. According to the criteria of the LAGA (1994), METHA fine sand can be categorized with the help of the toxin concentration shown in Table 2. It represents the category "restricted use dependent integration" whereby most values would allow even for a classification into the category "unlimited utilization". Therefore the prerequisites are given for utilization of fine sand. The possibilities in the cement industry, chalk-sand stone industry or also concrete industry must be mentioned, since METHA fine sand can be inserted as raw material alternative for pulverized sand. Contacts with the industries were already established, and utilization trials and investigations will be carried out in the course of the business of the large test plant. Utilization in road construction, for example, in asphalt production is possible. Required investigations for certification of fine sand to be permitted as building material are already under way. Altogether the goal of all efforts appears to create a high demand market product after termination of the investigation phase. The fine silt fraction out of the 20 Ilm separation is supposed to be utilized primarily in hill building. In the course of the now running test plant, also the yet unanswered questions are supposed to be examined. For example the behaviour of fine silt under integration conditions in a hill is not known. Also the soil mechanical installation parameters will be examined. Further possibilities for utilization, both for the conventional silt and fine silt is the brick production. The Hamburg company HZG-Hanseaten-Stein Ziegelei GmbH has succeeded in developing a production methodology that makes it possible to manufacture high-value ceramic building materials such as wall bricks, building bricks, cobblestones, using dredged material such as the Elbe River sediments. The research and development reached a level in 1993, which appears to realize these ideas in the framework of a larger plant and for industrial production. After many years of planing, certification, and building, and with an investment of almost 20 million OM for production and environmental protection arrangements, the HZG, a medium size Hamburg company, built a large technical demonstration site for brick production. The site is the only one of its kind world wide, also regarding the plant safety and waste gas cleaning technology in the construction material industry. The production capacity of the brick plant in Hamburg-Neuenfelde is approx. 5 million bricks per year.
In Figure 4 the basic flow of the technology is shown. Using dredged material instead of natural clay minerals in the production of bricks places especially high demands on the preparation, shaping and bum process of the input materials. In addition, it requires, from environmental protection aspects, the highest possible cleaning and supervision of emissions that may occur during the production process. Because these criteria are given with the Hamburger technology, a contract was set up accordingly at the end of 1995 between the HZG and Strom- und Hafenbau. The contract agrees to provide the METHA silt delivery for the 3-4 year demonstration period of up to 30.000 t METHA silt. With the current technical large scale investigations at the demonstration brick production in Hamburg-Neuenfelde, the required framework parameters are supposed to be determined. The aim is to reach an economically and ecologically wise technology of the dredged material utilization for the future.
New technology of mechanical treatment
343
I1IlurII ferroglnoul IIdlmlllll clay . . . . METHA lilt
Figure 4. Simplified flow sheet of METHA fine sand process
REFERENCES Detzner, H. D., Kitschen, L. and Weimerskirch, W. (1993). METHA - the first large-scale plant for treatment of harbour sediments. Aufbereitungstechnik/ Mineral Processing, 34(5), 235-242. Detzner, H. D. (1995). The Hamburg project METHA: large-scale separation, dewatering and reuse of polluted sediments. European Water Pollution Control, 5(5), 38-42. Glindemann, H. (1997). The development of Hamburgian concepts to handle dredged material. International Conference on Contaminated Sediments, September 7 - I I, 1997, Rotterdam Kroning, H. (1990). Separation and dewatering of fine-grained organic-mineral dredgings. Aufbereitungstechnik / Mineral Processing, 31(4), 205-214. LAGA - Uinderarbeitsgemeinschaft Abfall (1994). Anforderungen an die stoffliche Verwenung von mineralischen Reststoffen/Abfiillen - Technische Regeln - 20/1, Erich Schmidt Verlag, Berlin. Netzband, A. (1994). Dredged material management in the port of Hamburg. European Water Pollution Control, 4(6), 47-53.