Waste Water Treatment in Hamburg

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1 Waste Water Treatment in Hamburg Course work Author: Lecture: Waste Water Treatment ( ) Date: Lecturer: Doc.Ing. Pavel Hoffman, CsC Department: Process Engineering U218 Faculty: Faculty of Mechanical Engineering University: Czech Technical University in Prague Page 1 of 1

2 TABLE OF CONTENTS: 1 PREFACE HISTORICAL SITUATION CURRENT SITUATION THE WASTE WATER NETWORK OF HAMBURG THE WASTE WATER LOOP IN HAMBURG IN NUMBERS HAMBURG S WASTE WATER TREATMENT PLANTS WWTP HAMBURG-KÖHLBRANDHÖFT AND HAMBURG- DRADENAU PROCESS SCHEME MECHANICAL TREATMENT Raking System Sand trap Primary Sedimentation BIOLOGICAL TREATMENT Activated Sludge Tank Final Clarifiers...10 Page 2 of 14

3 4.4 CHEMICAL TREATMENT Precipitation of Phosphates Sludge Water Treatment SLUDGE TREATMENT PROCESS SCHEME SLUDGE DECAY / DIGESTION SLUDGE DEWATERING AND DRYING SLUDGE COMBUSTION AND HEATING REFERENCES Page 3 of 14

1 Preface This essay has been written as a course work for the lecture Waste Water Treatment (218 1089) during the author s Exchange semester at the Czech Technical University in Prague in the winter

4 1 Preface This essay has been written as a course work for the lecture Waste Water Treatment ( ) during the author s Exchange semester at the Czech Technical University in Prague in the winter semester The essay is supposed to be handed in to the lecturer, Doc.Ing. Pavel Hoffman, CsC, to gain the Assessment (Zapocet) for the abovementioned course. The essay describes both the historical and the current system of waste water treatment in the author s hometown, Hamburg. Hamburg is a city located in the northern part of Germany and has around 1,7 million inhabitants. It is the second largest city of Germany and situated 290 km from Berlin, the capital city of Germany with 3,3 million inhabitants. While the historical part of the essay gives a Hamburg, its rivers and its districts short overview about the development of waste water treatment regulations, developments and mechanisms in Hamburg, the emphasis of this essay is to describe the current situation. Therefore, a short summary of the organisational structure of waste water treatment in Hamburg is followed by a detailed description of the current waste water sewer network. Finally, the process mechanisms of the two waste water treatment plants of Hamburg, Köhlbrandhöft and Dradenau, are described in detail. 2 Historical Situation The development of an organised waste water treatment system in Hamburg started in the year Before this date, waste water was dispensed by houses directly into the streets, where especcially in the times of low rain it caused severe pollution of the streets and impacts to both environment and health. The streets have been cleaned by the rain which flushed the waste water to the Alster river or to the Elbe river, the two rivers that cross Hamburg. This resulted in a very bad quality of drinking water, which also caused severe health risks. Therefore, the local government issued laws that forbid Page 4 of 14

5 to use unfiltrated river water for drinking purposes. In addition to this, the local government tried to clean the streets of the city in irregular shifts by using cleaning trolleys and staff that tried to remove parts of the dirt layers. This dirt normally was disposed outside of the city. Normally, water in Hamburg has been sold by water boys, who nevertheless sometimes used the unfiltrated Elbe or Alster water. Due to the fact that Hamburg is a harbor city, there also have been problems concerning rats and other animals whose dirt also brought severe risks. In the year 1814, the local government therefore issued a law that forbid to dispose dirt in the streets and in the Elbe and Alster river. This law, although it did not achieve substantial health improvements, can be seen as the first step of an organised waste water and dirt treatment. After a large fire in Hamburg in the year 1845, the local government finally started to create a sewer system the first one in continental Europe which has been planned by the British engineer William Lindley. His plans have been realised extremely fast, which resulted in the first 11 km of sewers who were in use even in the same year. In 1860, already 48 km of sewers have been built and in 1890, the local government stated officially that all houses of Hamburg s city have been connected to the waste water sewer network. 3 Current Situation 3.1 The Waste Water Network of Hamburg The first waste water network in Hamburg is the oldest network of continental Europe and has a length of 943 km. The sewers called Siele in Hamburg are up to 4,70 m width and 3,85 m height and many of the first sewers are still in use. After the Second World War, beginning from 1967, a second network of sewers has been built to release the older network and to ensure the possibility of reconstruction and renewing of the old network. This Sewers in Hamburg Page 5 of 14

second network has a length of 4.471 km and consists of sewers with diameters of 20 cm up to 3,5 m.

6 second network has a length of km and consists of sewers with diameters of 20 cm up to 3,5 m. From 1990 onwards, both sewer networks have been reconstructed continuously which resulted in an average amount of investments from 20 Mio. Euro in 1990 up to 65 Mio. Euro in In 1995, the Hamburg sewer network has been privatized and the owning company, Hamburger Stadtentwässerung (hereafter called HSE) has been established. From this time on, investments have been intensified which resulted in an average investment of around 150 Mio. Euro per year for reconstruction and renewing of the The flag of HSE (Hamburger Stadtentwässerung) sewer system. HSE owns and maintains the Hamburg sewer network and the two waste water treatment plants in Hamburg, Köhlbrandhöft and Dradenau, both situated near the harbor. Both treatment plants have been built from 1955 onwards, additionally in 1988 a biological cleaning system has been created. 3.2 The Waste Water Loop in Hamburg in Numbers The daily average water consumption in Hamburg is 119 liters per capita. This means that per day around m³ of waste water need to be treated if it is not raining. This results in between 4 and 5 m³ per second. When it is raining, the volume of waste water rises up to 17 m³ per second. Per year, HSE cleans around 140 million cubic meters of waste water. The waste water treatment plants and the Hamburg sewer network are connected to 1,8 mio inhabitants and 0,4 mio equivalents of inhabitants that result from industrial and commercial waste water. Page 6 of 14

3.3 Hamburg s Waste Water Treatment Plants The two waste water treatment plants in Hamburg, Köhlbrandhöft and Dradenau, clean the waste water of Hamburg following the three main steps of cleaning

7 3.3 Hamburg s Waste Water Treatment Plants The two waste water treatment plants in Hamburg, Köhlbrandhöft and Dradenau, clean the waste water of Hamburg following the three main steps of cleaning mechanisms: First, the waste water is treated mechanically and cleaned from large impurities. This step is followed by a biological treatment and finally by a chemical treatment. After the cleaning, the water is discharged into the Elbe river. During the cleaning steps, an average amount of m³ of sludge is gained. This sludge, together with around tons of organic waste which belongs third industrial clients and is treated by the waste water treatment plants on contracts, is also used. The sludge decays The WWTPs Köhlbrandhöft and Dradenau in digestion towers (they can be seen in the picture on the right hand side) and produces carbonhydrogens from which electricity is gained. Furthermore, the sludge is dewatered and dried and finally it is used for heating purposes. All steps will be explained in detail in the following paragraphs. 4 WWTP Hamburg-Köhlbrandhöft and Hamburg-Dradenau 4.1 Process scheme The waste water treatment plants Köhlbrandhöft (mechanical, biological and chemical treatment) and Dradenau (biological treatment) operate after the following scheme. English translations and explanations of the included steps are prepared below. Page 7 of 14

Thermische Verwertung Process scheme of WWTPs Köhlbrandhöft and Dradenau Explanation of terms: German English Zulauf inlet mechanische Abwasserbehandlung mechanical WWT Rechen rake Sandfang sand trap

8 Thermische Verwertung Process scheme of WWTPs Köhlbrandhöft and Dradenau Explanation of terms: German English Zulauf inlet mechanische Abwasserbehandlung mechanical WWT Rechen rake Sandfang sand trap Vorklärbecken primary sedimentation tank biologische Abwasserbehandlung biological WWT Belebungsbecken activated sludge tank Nachklärbecken final clarifier Ablauf outlet Sandfanggut trapped material Sandwäsche cleaning of the sand Schlamm sludge Thermische Verwertung thermal utilisation zentrale Schlammbehandlung central sludge treatment (see chapter 5) Page 8 of 14

4.2 Mechanical Treatment 4.2.1 Raking System The Raking System The very first step of cleaning the waste water from the sewer inlet is a system of rakes that separate large impurities.

9 4.2 Mechanical Treatment Raking System The Raking System The very first step of cleaning the waste water from the sewer inlet is a system of rakes that separate large impurities. Per year around tons of material is separated by the raking system. This material is dewatered in a second step and is used for heating purposes together with the sludge Sand trap The sand trap is used to separate sand and other heavy impurities from the waste water. The flow rate and velocity within the sand trap is very low, which results in around 3,5 tons of sand and other material on non-rainy days. On days of heavy rain, this amount can rise up to 20 tons of separated material. This material around tons per year is mostly used for civil engineering purposes Primary Sedimentation The sand trap is followed by several tanks of primary sedimentation. Caused by different velocities in the different tanks, each tank produces sludge with specific matters regarding the mass of the sedimented impurities. These sludges are separated from the waste water, sieved, concentrated and finally they are used for the production of decay gases in the digestion towers. Page 9 of 14

10 4.3 Biological Treatment Activated Sludge Tank The biological treatment of the mechanically cleaned waste water aims to reduce the amount of carbons and nitrogens in the waste water without the use of chemicals. The reduction is obtained by the use of microorganisms that live in the activated sludge. Those microorganisms decay carbons and nitrogens within their metabolism and produce separable flocks of activated sludge. The microorganisms are predominantly aerobic organisms, therefore a large amount of oxygen is needed to ensure there metabolism. For this purpose, surface aerators are used Final Clarifiers The separation of the activated sludge takes place in the final clarifiers, which are the second and also the last step of the biological treatment. The separated activated sludge is mixed with new mechanically treated waste water and discharged to the activated sludge tanks therefore it is used in loops. Caused by continuously reproduction of microorganisms, the amount of activated sludge rises; to ensure a constant level of sludge within the process, a part of the sludge is concentrated and used for decay purposes in the digestion towers. 4.4 Chemical Treatment Precipitation of Phosphates The waste water within the treatment plants contains besides biological also chemical impurities, especially phosphates, which need to be separated. Therefore, the chemical treatment of biologically cleaned waste water is implemented as the third step of waste water treatment. Phosphates are separated by precipitation by adding ferric salts after the steps of mechanical treatment. Those salts and the phosphates form flocks that can be separated together with the activated sludge. Page 10 of 14

11 4.4.2 Sludge Water Treatment During the process of sludge dewatering, a certain amount of sludge water called Zentrat is separated. Although the volume of this water is nearly negligible, its pollution especcially with nitrogen is very high. This leads to the fact that around 30% of the whole nitrogen-caused pollution is connected to the Zentrat. Therefore, this relatively small volume flow is treated in a separate mechanism. HSE created an operation method called»store and Treat«, within which the sludge water is treated biologically and chemically. The outstanding step of this method is that in one tank both storage and treatment takes place. This not only increases process efficiency and economic, but also leads to around kg of separated nitrogen per day and to a significantly cleaner outlet effluent to the Elbe river. 5 Sludge treatment 5.1 Process scheme The separated sludge from the mechanical and biological treatment together with biologic waste of third clients is finally treated following this scheme; English explanations will be provided below. Process scheme of WWTPs sludge treatment Page 11 of 14

Explanation of terms: German Primärschlamm Faulgas Wärme Rauchgas Eindickung Anaerobe Fällung Entwässerung Trocknung Verbrennung Abgasreinigung Überschuss-Schlamm Zentrat Luft Asche, Reststoffe

12 Explanation of terms: German Primärschlamm Faulgas Wärme Rauchgas Eindickung Anaerobe Fällung Entwässerung Trocknung Verbrennung Abgasreinigung Überschuss-Schlamm Zentrat Luft Asche, Reststoffe English primary sludge digestion gas heat flue gas densification anaerobic precipitation sludge dewatering sludge drying sludge combustion flue gas cleaning sludge from final clarifiers sludge water air ashes, residues 5.2 Sludge Decay / Digestion The separated and densified sludge from the waste water treatment is pumped into ten sludge digestion towers with a volume of cubic meters each for sludge decay. Under continuous recirculation and a temperature of around 35 C, the sludge decays anaerobically. Bacteria decompose around 50% of the organic material and produce methane, carbon dioxide and water; organic nitrogen compounds are converted to water soluble ammonium compounds. Sludge digestion towers Per day, around kubic meters of digestion gases are produced. Those are used for electricity production by another company,»vera GmbH«. Page 12 of 14

For decaying purposes, also other organic residues from third parties, e.g. grease separator residues or sludges from other waste water treatment plants, can be used. Per year, around 26.

13 For decaying purposes, also other organic residues from third parties, e.g. grease separator residues or sludges from other waste water treatment plants, can be used. Per year, around tons of organic residues not originating from the Köhlbrandhöft and Dradenau treatment plants are decayed by HSE following contracts with industrial clients. 5.3 Sludge Dewatering and Drying For the dewatering and drying of the sludge, an own plant called KETA is used situated within the Köhlbrandhöft plant. The name is originated from the German name Klärschlamm-Entwässerungs-Trocknungs-Anlage (sludge dewatering and drying plant). In a first step using six centrifuges, the sludge is dewatered from 97% to nearly 80% which means that the sludge volume is decreased to the seventh part. Afterwards, the sludge is coated on steam-heated disc bed driers and is dried; after this step, it contains only around 58% of water. The steam for the heating of the discs is produced at the sludge combustion and by that used in loops without the need of additional energy input. By using KETA, the sludge volume is Sludge dewatering and drying plant KETA decreased from 1.3 million cubic meters to cubic meters per year which means that the volume is reduced by over 90%. Additionally to the sludge produced by the Hamburg waste water treatment plants, around tons of other residues per year are treated by KETA, mostly sludges from other municipal waste water treatment plants in the near region. 5.4 Sludge Combustion and Heating The dewatered and dried sludge is finally used for heating purposes. This step, implemented in the end of 1997, is the last step of the waste water treatment process in Hamburg. The plant for sludge combustion, VERA, is operated by»vera Klärschlammverbrennung GmbH«for HSE. The name VERA originates from the Page 13 of 14

14 German VErwertungsanlage für Rückstände aus der Abwasserbehandlung (plant for utilisation of waste water treatment residues). VERA combusts the dewatered and dried sludge and also the separated material from the raking systems. The sludge combustion is realised in three separate lines using fluidised bed combustion. Both technology and operation are environmentally-friendly and fulfill strict environmental regulatories. This ensures not only a very clean flue gas but also the possibility to operate the plant for long periods of time without the need of Sludge combustion plant VERA rearrangement. The residue of the combustion plant is an amount of ash of around 48 tons per day, which can be used as building material after it is melted. In a second step, the flue gases are cleaned which results in another six tons of plaster, also used as building material. The only waste that cannot be used is the heavy metal sludge 210 tons in the year 2004 which needs to be treated as hazardous waste. Compared with the total amount of separated waste water sludge, this sludge counts for less than 0,02%. Similar to the sludge digestion process and to KETA, also the VERA plant combusts additional waste from third customers. This counts for another tons. 6 References The information included in this essay originates mostly from material of Hamburger Stadtentwässerung (HSE) received from the company s website Additionally, information used in chapter one has been received from Wikipedia, and information used in chapter two has been received from the Hamburg Authority of Urban Development and Environment and from the municipal website Page 14 of 14

Proposal by Russia to delete hot sub-spot Hot sub-spot name South-West Wastewater Treatment Plant

Proposal by Russia to delete hot sub-spot 18.4 LAND 14/2009, Document 6/3/Rev.1 ATTACHMENT 1. Hot sub-spot name South-West Wastewater Treatment Plant 2. Location Block 2, 123, Volkhonskoye shosse, St.