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Integration of powdered activated carbon in tertiary disc filtration of wastewater

Thörnqvist, Elias LU and Isgaard, Philip (2016) VVA820 20161
Chemical Engineering (M.Sc.Eng.)
Abstract
This thesis investigates the feasibility of integrating Powdered Activated Carbon (PAC) in to chemical treatment in combination with disc filtration of tertiary wastewater. Jar and tube tests have been performed, where the suspension was filtered through a 10 μm disc filter from Hydrotech Veolia Water Technologies. The effluent has been analyzed for total phosphorus (TP), total suspended solids (TSS), number of particle per ml and turbidity to evaluate the efficiency of the experiments. The PAC can be used to adsorb micropollutants, which are small organic molecules derived from e.g. pharmaceuticals and hormones which are starting to impose problems in the aquatic environment as many of these are not treated in normal wastewater treatment... (More)
This thesis investigates the feasibility of integrating Powdered Activated Carbon (PAC) in to chemical treatment in combination with disc filtration of tertiary wastewater. Jar and tube tests have been performed, where the suspension was filtered through a 10 μm disc filter from Hydrotech Veolia Water Technologies. The effluent has been analyzed for total phosphorus (TP), total suspended solids (TSS), number of particle per ml and turbidity to evaluate the efficiency of the experiments. The PAC can be used to adsorb micropollutants, which are small organic molecules derived from e.g. pharmaceuticals and hormones which are starting to impose problems in the aquatic environment as many of these are not treated in normal wastewater treatment plants (WWTPs) today.

The chemical treatment of water is a two-step process where coagulant in the form of AlCl3 and flocculant as a cationic polymer is added to bind small particles in to bigger agglomer- ates. The PAC, coagulant and flocculant has been added in different orders and with two dif- ferent doses of PAC to examine how this affected the process and what was most benifical in terms of effluent quality. In addition to dosing and order of addition, the PAC’s effect on the wastewater without chemicals and its effect on disc filters were also investigated, showing that PAC itself adsorbs TP and has an accumulative effect on the filter cloth despite being thoroughly cleaned before each filtration.

The results were very promising when using 20 mg/l of PAC added either first, after or at the same time as the coagulant, always followed by the flocculant last. Lowering the mixing speed after adding the flocculant also showed a good floc formation and a very clean effluent. The exact order of addition regarding PAC should be deciding after examining its ability to adsorb micropollutants, something that was not investigated in this study.

The conclusion is therefore that it is feasible to integrate the addition of PAC in to chemical treatment in combination with Hydrotech’s disc filter, although further research and optimizing should be conducted when applying these experiments in a pilot plant regarding doses and where in the process to add PAC.

Since it is shown that PAC can be integrated without disrupting coagulation and flocculation, the plan is to send samples based on experiments produced in thesis to Århus University for analyses on the reduction of micropollutants in the water. (Less)
Popular Abstract (Swedish)
Mikroföroreningar är små molekyler som är restprodukter från t.ex. läkemedel, hormoner, kosmetika samt mikroplaster. Då majoriteten av dessa inte renas i våra av- loppsreningsverk har mikroföroreningarna börjat ackumuleras i vattendrag och dess negativa inverkan på vattenlevande djur har börjat uppmärksammas.

En av metoderna för att ta hand om och avskilja mikroföroreningarna i reningsprocessen är att tillsätta pulveriserat aktivt kol (PAK). PAK är en form av behandlad kol som har en förbättrad förmåga att fånga upp partiklar så som mikroföroreningar. I detta examensarbete undersöktes därför om PAK kunde integreras i ett av de senare reningsstegen av avloppsvatten och se om kolet kunde avskiljas med hjälp av kemisk rening, där man... (More)
Mikroföroreningar är små molekyler som är restprodukter från t.ex. läkemedel, hormoner, kosmetika samt mikroplaster. Då majoriteten av dessa inte renas i våra av- loppsreningsverk har mikroföroreningarna börjat ackumuleras i vattendrag och dess negativa inverkan på vattenlevande djur har börjat uppmärksammas.

En av metoderna för att ta hand om och avskilja mikroföroreningarna i reningsprocessen är att tillsätta pulveriserat aktivt kol (PAK). PAK är en form av behandlad kol som har en förbättrad förmåga att fånga upp partiklar så som mikroföroreningar. I detta examensarbete undersöktes därför om PAK kunde integreras i ett av de senare reningsstegen av avloppsvatten och se om kolet kunde avskiljas med hjälp av kemisk rening, där man tillsätter en koagulant (metallsalt) och en flocculant (polymer) för att fånga upp partiklar, samt skivfilter från Hydrotech Veolia Water Technologies för att filtrera bort dessa från vattnet. Skivfilter används ofta i ett senare steg i en reningsprocess där dess små porer används för att ”polera” vattnet, alltså ta bort en finfraktion av oönskade små partiklar.

Resultaten pekar på att metoden fungerar för att avskilja kolpartiklarna vilket skulle kunna betyda att inom en snar framtid kan avloppsreningsverk separera en stor del av de svårfångade problemmolekylerna. Detta skulle vara till en stor fördel för liv i vattenmiljö men inte minst för oss själva då mikroföreningarna även går att finna i dricksvatten!

I examensarbetet har studenter på LTH utfört småskaliga experiment där kemisk rening av avloppsvatten genomförts i samband med tillsats av PAK i vattenlösning. Avloppsvatten har hämtats från Källby avloppsreningsverk och med hjälp av den kemiska reningen lyckats binda kolet samt andra föroreningar. Vattnet och kemikalierna har låtits reagera och sedan skivfiltrerats innan det resulterande utflödet analyserats för att undersöka vattenkvaliteten.

Dessa experiment har varit en del av ett större forskningsprojekt benämnt RESVAV (Rening av svårnedbrytbara ämnen från avloppsvatten) som drivs av Havs- och vattenmyndigheten. De lyckade resultaten innebär att vidare forskning kommer att bedrivas och förhoppningen är att i framtiden på ett lyckat sätt kunna avskilja mikroföreningar i reningsverk. (Less)
Please use this url to cite or link to this publication:
author
Thörnqvist, Elias LU and Isgaard, Philip
supervisor
organization
course
VVA820 20161
year
type
H2 - Master's Degree (Two Years)
subject
keywords
vattenförsörjningsteknik, water engineering, environmental engineering, flocculation, coagulation, PAC, discfilters, Micropollutants, Powdered activated carbon, avloppsteknik
report number
2016-10
language
English
id
8884673
date added to LUP
2016-06-28 11:39:58
date last changed
2016-06-28 11:39:58
@misc{8884673,
  abstract     = {This thesis investigates the feasibility of integrating Powdered Activated Carbon (PAC) in to chemical treatment in combination with disc filtration of tertiary wastewater. Jar and tube tests have been performed, where the suspension was filtered through a 10 μm disc filter from Hydrotech Veolia Water Technologies. The effluent has been analyzed for total phosphorus (TP), total suspended solids (TSS), number of particle per ml and turbidity to evaluate the efficiency of the experiments. The PAC can be used to adsorb micropollutants, which are small organic molecules derived from e.g. pharmaceuticals and hormones which are starting to impose problems in the aquatic environment as many of these are not treated in normal wastewater treatment plants (WWTPs) today.

The chemical treatment of water is a two-step process where coagulant in the form of AlCl3 and flocculant as a cationic polymer is added to bind small particles in to bigger agglomer- ates. The PAC, coagulant and flocculant has been added in different orders and with two dif- ferent doses of PAC to examine how this affected the process and what was most benifical in terms of effluent quality. In addition to dosing and order of addition, the PAC’s effect on the wastewater without chemicals and its effect on disc filters were also investigated, showing that PAC itself adsorbs TP and has an accumulative effect on the filter cloth despite being thoroughly cleaned before each filtration.

The results were very promising when using 20 mg/l of PAC added either first, after or at the same time as the coagulant, always followed by the flocculant last. Lowering the mixing speed after adding the flocculant also showed a good floc formation and a very clean effluent. The exact order of addition regarding PAC should be deciding after examining its ability to adsorb micropollutants, something that was not investigated in this study.

The conclusion is therefore that it is feasible to integrate the addition of PAC in to chemical treatment in combination with Hydrotech’s disc filter, although further research and optimizing should be conducted when applying these experiments in a pilot plant regarding doses and where in the process to add PAC.

Since it is shown that PAC can be integrated without disrupting coagulation and flocculation, the plan is to send samples based on experiments produced in thesis to Århus University for analyses on the reduction of micropollutants in the water.},
  author       = {Thörnqvist, Elias and Isgaard, Philip},
  keyword      = {vattenförsörjningsteknik,water engineering,environmental engineering,flocculation,coagulation,PAC,discfilters,Micropollutants,Powdered activated carbon,avloppsteknik},
  language     = {eng},
  note         = {Student Paper},
  title        = {Integration of powdered activated carbon in tertiary disc filtration of wastewater},
  year         = {2016},
}