• No results found

The water treatment system at Djupdalen

N/A
N/A
Protected

Academic year: 2022

Share "The water treatment system at Djupdalen"

Copied!
25
0
0

Loading.... (view fulltext now)

Full text

(1)

Avdelningen för energi-, miljö- och byggteknik

The Water Treatment System at Djupdalen

Rebeca Guerra Garlito

Date/Term: HT 2007 Supervisor: Ola Holby Examiner: Roger Renström

(2)

Abstract

This is a project about The Water Treatment System at Djupdalen.

The leakage water comes to the Water Treatment System from a deposition plant through the land. The leakage water is characterized by a high concentration of nitrogen and the system is based on biological removing of the nitrogen in the water, by nitrifying and denitrifying bacteria.

Four different problems are found in the system:

1. High level of nitrogen concentration in the outgoing water of the system. It should be due to the lack of phosphate in the water, that do not let the bacteria to grow.

2. Low temperature during the most part of the year. Nitrifying and denitrifying bacteria are temperature-dependent, that are very slow at low temperatures.

3. High oxygen concentration in one of the anoxic pond, where the denitrification process take place. This oxygen concentration is too high for denitrifying bacteria to work.

4. The nitrification and denitrification bacteria need to be “old” to work efficiently.

They need a surface to attach, because if not they flow with the water and they leave the system.

And four possible solutions for the system are presented:

1. Phosphate should be added to the system to let bacteria growth.

2. Store the water at a store pond during the winter months and transport it to the system when the temperature is optimum for the bacteria to work.

3. Add carbon matter to improve the carbon oxidation and to low down the oxygen levels at the anoxic ponds.

4. Two options are presented to improve the system, the first one is based on the construction of a dark wavy bottom in the channel system, which will give a surface for bacteria to attaché, it will produce oxygenation in the water, and it will also improve the water temperature; and the second one is based on the addition of panels made of black material, which will give to bacteria a surface to attach, and improve the water temperature.

(3)

Contents

Introduction………...………..………3

Water Treatment System at Djupdalen ……..………..………...……4

Theoretical aspects………..………5

Material and Methods…………..……….…...….7

Results……….……7

Discussion and analysis……..………...………18

Concluding remarks……….………...……..23

References………..……….………..24

(4)

Introduction

This project is performed at The Water Treatment System at Djupdalen.

In this project, the theoretical aspects of a water treatment system are explained and the Djupdalen system is studied into detail. Then, possible solutions for the system are presented.

The theme of this project is: How can the Water treatment system at Djupdalen be improved? And, what are the possible adjustments in the system?

The possible problems in the system are investigated into the following aspects to study:

 Temperature

 Ph

 Retention times in the system

 Oxygen concentration

 Carbon concentration

 Phosphate concentration

 Bacteria

All these aspects are studied into detail and the goal is to find solutions to improve the system.

(5)

The Water Treatment System at Djupdalen

The following image shows The Leachate Treatment System at Djupdalen:

Image 1: The Djupdalen Water Treatment System

The Water Treatment System at Djupdalen is based on a biological mechanism to remove the pollution substance of the leakage water.

The leakage water comes to the Leachate Treatment System from a deposition plant through the land; it arrives to the first pond where the wastewater is stored. From this pond, the water is transported by a pipe to the Leachate Treatment System.

The water comes into an aerated pond (P1 at the image), where there are four aerators working to give oxygen to this pond in order to help the bacteria to grow. Nitrifying bacteria were added directly to this aeration pond. The nitrification process occurs in this pond by the action of the nitrifying bacteria (the process is going to be explained at the next section).

After the aerator pond the water goes to a channel system (P2 at the image), where the water runs at slow velocity and at a shallow level. There is a reed bed that also helps to

(6)

percentage of the nitrogen of the water. According to authors referred to by Wrigley and Toerien (1988), the removal potential for Phragmites ranges from 330 to 880 kg N/Ha (Etnier and Guterstam, 1997)

After the channel system the water is transported to two anaerobic ponds (P6 at the image), where the denitrification process should occur. The oxygen levels are reduced at minimum by the biological oxidation.

And finally the water runs out of the system (P3 at the image), and transported to a river.

Theoretical aspects

The wastewater that comes into The Leachate Treatment System at Djupdalen from the deposition plant is characterised by a high concentration of nitrogen.

Nitrogen can be removed by denitrification, adsorption of ammonia by the soil, or uptake by plants (Etnier and Guterstam, 1997)

Nitrification and denitrification process:

Nitrification process:

This process requires oxic conditions in the system. This process occurs in to steps, by two different kinds of bacteria:

The first step is the oxidation of the ammonium to nitrite. This reaction is carried out by nitrifying bacteria, the most common bacteria is the Nitrosomona:

2NH4+ + 3O2 → 2NO2- + 4H+ + 2H2O

In the second step the nitrite is oxidized to nitrate by the action of another kind of nitrifying bacteria, the most common bacteria is the Nitrobacter:

2NO2- + O2 → NO3-

The general chemical formula for this process can be written as follows:

(7)

2NH4+ + 4O2 → 2NO3- + 4H+ +2H2O The nitrification process is influenced by:

- Temperature higher than 8ºC. Optimum temperature: 25º- 30ºC - PH between 7-8.5

- Oxygenconcentration higher than 2mg/l.

Denitrification process:

Denitrification is the process where nitrate is reduced to N2(gas) by the action of denitrifying bacteria, with nitrate as an intermediate stage. Finally, the nitrogen gas is lost to the atmosphere.

This process requires anoxic or close to anoxic conditions and carbon sources.

[CH2O] (Organic matter) + NO3- → NO2- → NO → N2O → N2

Nitrate is one of the first utilized electron acceptors during the decomposition of organic matter (anaerobic respiration).

Denitrification procces is controlled by:

- Temperature higher than 8ºC. Optimum temperature: 25º- 30ºC - PH between 7-8

- Oxygen concentration: anoxic or close to anoxic concentration - Nitrate concentration

- Organic carbon concentration

Nitrification retrains the rate of nitrification

Carbon oxidation:

This process consumes the oxygen in the water producing anoxic conditions in the system. This, in turn, improves the denitrification process

[CH2O] (Org mat) + O2 → CO2 + H2O

(8)

Material and Methods

This project is performed by the material proportionate for Alcontrol lab, which are published at the website of this lab. To understand how the system is working and to find the possible problems in it, all the information in this website was useful. Every month the analysis are realized and published, since 2005 October.

Also, the study was based on literature and measurements in field. Oxygen concentration and chemistry analysis of phosphate concentration were realized. Water samples from The Leachate Treatment System at Djupdalen were taken at several points in the system on date August 27th 2007. The phosphate determination was spectrophotometer according to Hach Lange LCK 350

Results

Graph 1 presents the incoming and outgoing flow in the system:

Flow

50000 10000 15000 20000 25000 30000 35000 40000 45000 50000

2005- 112006- 012006- 032006- 052006- 072006- 092006- 112007- 012007- 032007- 052007- 07

(m3/month)

Incoming Outcoming

Graph 1: Incoming and outgoing flow of the system

As is represented in the graph the higher flow coming to the system coincides with the month of higher raining and with the melting of the snow.

(9)

Nitrogen:

Graph 2 concerns the nitrogen concentration at the point 1, the incoming water into the system. It is shown at the graph: the ammonium concentration (blue line), the nitrite and nitrate concentration (green line) and the nitrogen total concentration (red line).

Graph 2: Nitrogen concentration at the point 1 (incoming) (Alcontrol 2007)

The higher incoming concentration of nitrogen corresponds with the winter months in both years.

(10)

Graph 3 shows the concentration of ammonium (blue line), nitrate and nitrite concentration (green line) and the total nitrogen concentration at the point 2 of the system, corresponding with the outgoing water from the aeration pond.

Graph 3: Nitrogen concentration at the point 2 (Alcontrol 2007)

At this point of the system, the concentration of ammonium is slightly reduced. And the nitrate and nitrite concentration are increased. In general, the total nitrogen amount at the system is not reduced.

(11)

Graph 4 the ammonium concentration (blue line), the nitrite and nitrate concentration (green line) and the nitrogen total concentration (red line) in the outgoing water of the system, is represented.

Graph 4: Nitrogen concentration at the point 3 (outgoing) (Alcontrol 2007)

At this part of the system the total concentration of nitrogen is slightly reduced as well as the ammonium concentration.

(12)

Graph 5 shows the measurements of nitrogen concentration at the three different points of the systems at the different times of the year: point 1 represents the incoming to the system, while point 2 is the outgoing from the aeration pond and point 3 is the outgoing water of the system.

Total Nitrogen concentration

0 20 40 60 80 100 120 140 160

2005- 102005-122006- 022006- 052006- 072006- 092006- 112007- 01 mar-07may-07 jul-07

(mg/l)

Point 1 point 2 point 3

Graph 5: Total nitrogen concentration at the system

In general, as is showed at the graph the total nitrogen concentration is decreasing along the system.

(13)

Graph 6 shows the ammonium concentration along the system, it is represented as the concentration each month at three different points of the system: point 1 concerns the incoming to the system, point 2 the outgoing from the aeration pond and point 3 the outgoing water of the system.

Ammonium concentration

0 20 40 60 80 100 120 140

2005- 10

2005-122006- 02

2006- 05

2006- 07

2006- 09

2006- 11

2007- 01

mar-07may-07 jul-07

(mg/l)

Point 1 point 2 point 3

Graph 6: Ammonium concentration at the system

The ammonium concentration decreases after point 1 and continuous decreasing along all the system, by the action of the nitrifying bacteria. The final values of ammonium concentration in the system are quite good at the warmer months, but during the winter months the values are high.

(14)

Graph 7 presents the nitrate and nitrite concentration in every month at three different points along the system: point 1 concern the incoming to the system, point 2 the outgoing from the aeration pond and point 3 the outgoing water of the system.

Nitrate + nitrite concentration

0 2 4 6 8 10 12 14 16

2005- 10

2005-12 2006- 02

2006- 05

2006- 07

2006- 09

2006- 11

2007- 01

mar-07 may-07 jul-07

(mg/l)

Point 1 point 2 point 3

Graph 7: Nitrate and nitrite concentration at the system

The Nitrate and nitrite concentration increases from the first to the second point to the system. After the second point, the concentration of both substances decreases.

(15)

Phosphate:

Graph 8: Phosphate concentration at the point 1 (incoming into the system) (Alcontrol 2007) (Concentration scale 1:10)

These phosphate concentrations in the incoming water are low during all the year. The maximum level was 0,14 8mg/l) on 2007 December.

Graph 9: Phosphate concentration at the point 2 of the system (Alcontrol 2007) (Concentration scale 1:100)

The phosphate concentration is low during both years. The maximum level was

(16)

Graph 10: Phosphate concentration at the point 4 of the system (Alcontrol 2007) (Concentration scale 1:10)

The maximum concentration was on 2006 august with 0,11 (mg/l).

Graph 11: Phosphate concentration at the point 5 of the system (Alcontrol 2007) (Concentration scale 1:10)

The phosphate concentration is low during all the time represented at the graph. The maximum level of phosphate at this point was on 2007 April with 0,37 (mg/l).

(17)

Graph 12: Phosphate concentration at the point 3 (outgoing of the system) (Alcontrol 2007) (Concentration scale 1:10)

The phosphate concentration at the outgoing water of the system is low. The maximum concentration is 0,17 (mg/l) on 2006 October.

(18)

The table 1 presents the oxygen and phosphate concentrations in the system:

Tª (ºC) Oxygen(mg/l) PO4 (mg/l)

P1 19,4 7.28 0,049

P2 16,3 2.97 0,056

1 16,1 5.51 0,065

2 16,1 6.82 0,055

P4 16,3 6.64 0,069

3 16,4 8.32 *

4 16,4 10.54 0,096

P5 16,6 10.34 *

Deep pond 1 16,1 0.36 *

Deep pond 2 15,2 2.32 *

P3 17,4 2.80 0,083

Table 1: oxygen and phosphate concentration at the different points in the system

(* There is no data)

As the table shows, the phosphate concentration along the system is very low.

(19)

Discussion and analysis

There are many different problems in the system, for all these reasons the system is not working as it should.

The flow levels are unlikely because at the last months of 2007 the outgoing flow is much higher than the incoming, which is almost impossible. This difference is due to the construction realized in the system at this time.

The concentration of nitrogen in the outgoing water is too high during the most part of the year. The ammonium concentration should decrease after the aerated pond due to the nitrification process and it should be transformed to nitrate. Then the nitrate concentration should increase at this part of the system.

After the nitrification process at the anoxic ponds, the levels of nitrate should decrease at maximum as well as the total levels of nitrogen in the water.

However, theses processes are not happening along the system. The total nitrogen concentration is slightly reduced. The final nitrogen concentration at the outgoing of the system is still high in the most part of the months, only during the warmer months this concentration is low.

The Phosphate concentration along the system is low.

Concerning to the oxygen concentration, the sample called 4 and P5, the values are very high, which is impossible, because of the saturation levels in the water, and must therefore be a mistake at the sampling measure.

The oxygen concentration at the deep pond 2 is high; at this part of the system the denitrification process should take place. Due to this oxygen concentration this process is not happening because the denitrification bacteria need anoxic conditions to work.

(20)

Problems and solutions:

1) The nitrogen level at the system is very high. The maximum level at the outgoing water must be lower than 30mg/l.

This problem could be derived from the lack of phosphate along the system, which does not let the bacteria to grow, and then the nitrification and denitrification process is not working as it should. The phosphate is limiting the bacteria growth.

The normal relation for the primary production, between Nitrogen and Phosphate in the water is:

7 (mg/l) N → 1 (mg/l) P

The average concentration of Nitrogen at the system is between 60-90(mg/l). Then the concentration of phosphate should be between 8,5-12 (mg/l), for a maximum bacteria growth.

The highest concentration of phosphate measured along the system is 0,37 (mg/l).

The possible solution for the lack of phosphate at the system is the addition of it.

This addition should be realized in according with the bacteria growth. To beginning, lower concentration of phosphate should be added to the system, and this addition will be increased in according with the bacteria growth, because if all the phosphate required is added at the same time, there will not be enough amounts of bacteria to use that phosphate and it will be lost with the water flow.

But the addition of phosphate should not be too high, because algal blooms and other precursors of eutrophication will appear if the phosphate concentration is high at the system.

2) The temperature is a problem during winter time. The system is only working satisfactory during the warmer months of the year, from May until November (approximately, it is depending on the temperatures of each year).

Biochemical reaction rates decrease with decreasing temperature and longer retention times might be necessary to achieve adequate purification. (Etnier and Guterstam,

(21)

A solution could be to store the water during those months when the temperature is very low, and transporting the water into the system during the warmer months.

During the winter the bacteria does not work due to the low temperature, and if the water is still running along the system, no process is happening in the water and the nitrogen still in it, going into the river and polluting the natural flow water.

If the water is stored during the winter and transported during the warmer months into the system, the flow will be too high for this leachate treatment system, and the retention times will not be enough for the bacteria to remove the nitrogen in the water.

A possible solution will be to store part of the water coming to the system during those winter months and the other part of the water will be conduct to the system though an underground pipe. If the temperature before the store pond is at least 8 degrees, part of the water can be stored and the other part of the water will go into the system. The water will not get colder and the system will continue to work.

The water temperature should be measured before the store pond during the winter time.

There is not enough data to give a full explanation.

Also, if the water is stored at a store pond before the system, the flow incoming to the system will be controlled. The water flow incoming to the system should be controlled in according with the temperature. And if the water flow is controlled, the levels of nitrogen incoming to the system will be controlled as well. Then, it will be easier to know how much phosphate is required in the system, and the addition of this will be realized.

3) The oxygen concentration at the anaerobic ponds should be lower than 1(mg/l). At the first one, the oxygen level is 0,36 (mg/l), which is really good. At the second pond the oxygen concentration is high, 2,32 (mg/l), and this oxygen level does not allow the denitrifying bacteria to work.

A solution for this problem is to add organic material at the anaerobic pond. The addition of organic material increases the carbon oxidation and the denitrification process.

(22)

4) The nitrifying and denitrifying bacteria need to be “old” to work satisfactory. They need a surface to attach, because if not they are flowing with the water and leaving the system.

A possible improvement in the system could be the construction at the channel system (since point 2 until point 5) a wavy bottom made of dark material. (See picture)

Image 2: Improvement at the Djupdalen Water Treatment System

The advantage of this construction at the channel system is that this bottom will give the bacteria a surface to attach.

This wavy bottom will help to absorb the energy from the sun. The dark material keeps the energy from the sun and it will give an increase of the water temperature.

Also this change at the bottom will produce aeration in the water system thanks to the turbulence created in the water flow.

(23)

Another possible improvement could be to adding up to the system panels made of dark material, as you can see in the following picture:

Image 3: Improvement at the Djupdalen Water Treatment System

This solution will give the bacteria a surface to attach.

Also, these dark panels will absorb the energy from the sun, keeping it inside; and increasing the water temperature.

The option for this solution will be adding these panels along the system, since the aeration pond until point 5; they will provide a place for bacteria to sit and increase of the water temperature.

5) Another problem is the pipes. Many times are blocked due to grass and other material running into the water flow. When the pipes are blocked the flow into the system is interrupted and the water does not run as normal flow.

The pipes must to be checked often to avoid to be blocked.

If many of these improvements are realized this system should work perfect and the

(24)

Concluding remarks

In conclusion, after the research work explained above, and according to the used sources The Leachate Treatment System at Djupdalen is an interesting project, and it could work perfectly if some solutions and improvements will be realized in the system.

At this time the system is not working as it should, due to many problems as they were explained before: temperature, phosphate concentration, bacteria, and oxygen levels.

A “Maintenance Plan” in the system must be set up. It should be checked at least once per month how the system is working:

1. The water quality: it must be continuous checked every month, along all the system.

And many solutions must be adopted to improve the quality of the outgoing water.

2. The phosphate concentration along the system: at the beginning of the warmer months bacteria should be added as well as the phosphate to avoid lack of this.

3. The oxygen concentration at the anoxic ponds: when these levels are high the solution must to be adopted, if not the system will not work as it should.

4. The pipes should be checked every month and after every storm.

(25)

References

• www.alcontrol.se : 2007-08-10

• Binnie Chirs, and others. 2002 “Basic water treatment”. Royal Society of Chemestry. ISBN: 0-85404-989-4

• Etnier, Carls and Guterstam, Bjorn. 1997 “Ecological Engineering for Wastewater Treatment”. Lewis Publishers. ISBN: 0-87371-990-5 (page 245)

• Holby Ola. 1991 Biogeochemical processes in fish farm deposits and weddell sea sediments. Department of analytical and marine chemistry Gothenburg.

• Kadlec, Robert H and Knight, Robert L. 1996 “Treatment Wetlands”. Lewis Publishers. ISBN: 0-87371-930-1

• Metcalf and Eddy. 2003 “Wastewater Engineering”. McGraw-Hill Higher Education. ISBN: 0-07-112250-8

• Weiner, Eugene R. 2000 “Applications of environmental chemistry”. Lewis Publishers. ISBN: 1-56670-354-9

References

Related documents

Byggstarten i maj 2020 av Lalandia och 440 nya fritidshus i Søndervig är således resultatet av 14 års ansträngningar från en lång rad lokala och nationella aktörer och ett

Omvendt er projektet ikke blevet forsinket af klager mv., som det potentielt kunne have været, fordi det danske plan- og reguleringssystem er indrettet til at afværge

I Team Finlands nätverksliknande struktur betonas strävan till samarbete mellan den nationella och lokala nivån och sektorexpertis för att locka investeringar till Finland.. För

The increasing availability of data and attention to services has increased the understanding of the contribution of services to innovation and productivity in

– Visst kan man se det som lyx, en musiklektion med guldkant, säger Göran Berg, verksamhetsledare på Musik i Väst och ansvarig för projektet.. – Men vi hoppas att det snarare

It could be said that system identication was established as a certied research eld within the automatic control area in the middle of the sixties: At the third IFAC Congress

Keywords: EU asylum policies, right to seek asylum, Greek border islands, multilevel governance, externalization of asylum,

Vernacular structures like these exist all over the world and are not exclusive to the Sámi design tradition, but this makes them no less part of the Sámi cul- ture...