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Evaluation of an Extended Aeration System for Nutrient Removal, A Case Study of a Wastewater Treatment Plant in Kulai, Johor Baharu, Malaysia

Ingvar-Nilsson, Caroline LU and Forså, Naima LU (2016) VVA820 20161
Chemical Engineering (M.Sc.Eng.)
Abstract
Malaysia is one of the most developed countries in Southeast Asia, and strives to be acknowledged as a high income country by the year of 2020. According to Malaysian Environmental Quality (Sewage) Regulations from 2009 there are effluent limitations regarding nutrient emission from wastewater treatment plants. The company responsible for the municipal wastewater treatment, Indah Water Konsortium, have found that the performances of nutrient removal at their wastewater treatment plants are varying and the company is interested in examining the reason for the difference. This study has investigated nutrient removal at one of Indah Water Konsortium’s wastewater treatment plants in order to evaluate how well it is working and what could be... (More)
Malaysia is one of the most developed countries in Southeast Asia, and strives to be acknowledged as a high income country by the year of 2020. According to Malaysian Environmental Quality (Sewage) Regulations from 2009 there are effluent limitations regarding nutrient emission from wastewater treatment plants. The company responsible for the municipal wastewater treatment, Indah Water Konsortium, have found that the performances of nutrient removal at their wastewater treatment plants are varying and the company is interested in examining the reason for the difference. This study has investigated nutrient removal at one of Indah Water Konsortium’s wastewater treatment plants in order to evaluate how well it is working and what could be done in order to improve the nutrient reduction.

The investigated wastewater treatment plant is an activated sludge plant with extended aeration and a primary treatment consisting of grit and grease removal. The characteristics of the influent wastewater are purely domestic. The plant is designed for 1216 population equivalents and at present 1160 population equivalents are connected.

The aims were to evaluate the nutrient reduction, analyse whether biological phosphorus removal called Bio-P could be possible and to give suggestions for possible upgrades and improvements of the plant. It was done by constructing a nitrogen and phosphorus mass balance. Also, analyses were performed to assess the nitrification rate, measure the amount of volatile fatty acids in the influent and basic parameters such as dissolved oxygen, pH, mixed liquor suspended solids and aerobic sludge age. Samples were taken three times a week during a five-week period starting from the 21st of March 2016.

The analyses showed that organic matter, measured as BOD and COD, were satisfactorily reduced. The nitrogen mass balances showed that nitrification and denitrification occurred, however the processes were uneven and not reliable. The results also showed that both the measured maximum and full-scale nitrification rate were very low which probably was due to low oxygen concentration and pH-levels in the aerobic tank. The mixed liquor suspended solids concentration and the aerobic sludge age was found to be enough for the bacteria to carry out the nitrification process, assimilate nutrients and for BOD-reduction.

The phosphorus mass balances showed that more phosphorus than expected was removed from the wastewater treatment plant; there was high phosphorus content in the sludge. The high removal may be due to Bio-P. Furthermore, investigations showed that there were enough volatile fatty acids in the wastewater to obtain Bio-P. If the characteristics of the wastewater are similar at other places, Bio-P could be an option for the future at wastewater treatment plants in Malaysia.

In order to upgrade the plant, calculations were made to evaluate if the size of the tank used for biological treatment is sufficient for nitrification and if there is space to incorporate an anoxic tank in order to get a predenitrification treatment. The results showed that with an expected nitrification and denitrification rate at the wastewater treatment plant the present volume is large enough for a pre-denitrification process. One of the main improvements that could be made at the wastewater treatment plant is to increase the nitrification rate by improving the aeration. (Less)
Popular Abstract (Swedish)
Bakterier och alger behöver, såsom andra organismer bl.a. kväve och fosfor för att växa. Dessa näringsämnen är begränsande i naturen men finns i höga koncentrationer i avloppsvatten. Stora mängder näringsämnen i naturen från exempelvis avlopp kan leda till övergödning och obalans i ekosystemen. För att kunna njuta av våra sjöar, åar och bäckar måste avloppsvatten renas, t.ex. genom. biologisk rening.

Flertalet biologiska reningsmetoder finns, bl.a. aktivslamanläggning, se figur 1. Slammet är aktivt pga. dess innehåll: levande organismer såsom bakterier. Ett malaysiskt avloppsreningsverk nära staden Johor Baharu med denna typ av rening var föremål för en fallstudie.

Reningen består av en stor luftad bassäng (1) med bakterier som... (More)
Bakterier och alger behöver, såsom andra organismer bl.a. kväve och fosfor för att växa. Dessa näringsämnen är begränsande i naturen men finns i höga koncentrationer i avloppsvatten. Stora mängder näringsämnen i naturen från exempelvis avlopp kan leda till övergödning och obalans i ekosystemen. För att kunna njuta av våra sjöar, åar och bäckar måste avloppsvatten renas, t.ex. genom. biologisk rening.

Flertalet biologiska reningsmetoder finns, bl.a. aktivslamanläggning, se figur 1. Slammet är aktivt pga. dess innehåll: levande organismer såsom bakterier. Ett malaysiskt avloppsreningsverk nära staden Johor Baharu med denna typ av rening var föremål för en fallstudie.

Reningen består av en stor luftad bassäng (1) med bakterier som kalasar på avloppsvatten samtidigt som de reducerar näringsämnen. Nästa bassäng delar slammet och vattnet (2). Det renade vattnet fortsätter till recipient som sedan leder ut i det malaysiska havet. Slammet recirkuleras till luftningsbassängen (3) eller behandlas (4). Även om bakterierna vid verket som undersökts inte fick tillräckligt med syre fungerade det ändå bra för dess ändamål: att rena från organiskt material som den gjorde med bravur. Hela 94 % av det organiska materialet reducerades.

Såsom vi människor behöver näringsämnen i lagom mängd, behöver bakterier en speciell sammansättning av näringsämnen. Men så är det sällan, vanligtvis finns det mycket kväve och fosfor kvar i vattnet. Bakterierna kan inte äta upp alla näringsämnen. Mer rening behövs! Kväve i vatten skapar övergödning medan kväve i luft är ofarligt. Idén är att om-vandla kvävet i vattnet till kvävgas vilket kan utföras av ett gäng speciella bakterier.

Kväve kommer till reningsverket vanligtvis som ammonium. I luftade miljöer kan ammonium omvandlas till nitrat m.h.a. speciella bakterier, processen kallas nitrifikation. Därefter kan nitratet bli kvävgas under anoxiska (inget fritt syre) förhållanden och det kallas denitrifikation. Och upp i luften försvinner kvävet! På verket var nitrifikationen hämmad p.g.a. den låga syrehalten. Detta hade i sin tur påverkan på denitrifikationen som inte kunde omsätta allt kväve till kvävgas.

Men, fosfor då? Lösningen heter bakterier! Denna speciella typ av bakterie kan ta upp extra mycket fosfor som sker i alternerade aeroba och anaeroba bassänger och processen kallas Bio-P. Fosforen hade högre reduktionsgrad än förväntat vilket kan förklaras av Bio-P.

Nitrifikation, denitrifikation och Bio-P kan installeras i en och samma process. Har man tur kan man till och med göra detta i en befintlig aktivslamanläggning om det finns tillräckligt med plats för att alla processer kan ske samt lite ombyggnation och anpassningar till de olika processera. Enligt utförda beräkningar finns det plats för både nitrifikation och denitrifikation. Det skulle förbättra reduktionen av kväve samt göra den mer stabil. Dataunderlaget begränsade tyvärr möjligheten för vidare analyser. (Less)
Please use this url to cite or link to this publication:
author
Ingvar-Nilsson, Caroline LU and Forså, Naima LU
supervisor
organization
course
VVA820 20161
year
type
H2 - Master's Degree (Two Years)
subject
keywords
Nutrients, Nitrogen, Extended Aeration, Nitrification rate, Phosphorus, Volatile Fatty Acids, Activated Sludge, Bio-P, water engineering, environmental engineering, vattenförsörjningsteknik, avloppsteknik
language
English
id
8890587
date added to LUP
2016-09-12 15:38:00
date last changed
2016-09-12 15:38:00
@misc{8890587,
  abstract     = {Malaysia is one of the most developed countries in Southeast Asia, and strives to be acknowledged as a high income country by the year of 2020. According to Malaysian Environmental Quality (Sewage) Regulations from 2009 there are effluent limitations regarding nutrient emission from wastewater treatment plants. The company responsible for the municipal wastewater treatment, Indah Water Konsortium, have found that the performances of nutrient removal at their wastewater treatment plants are varying and the company is interested in examining the reason for the difference. This study has investigated nutrient removal at one of Indah Water Konsortium’s wastewater treatment plants in order to evaluate how well it is working and what could be done in order to improve the nutrient reduction. 

The investigated wastewater treatment plant is an activated sludge plant with extended aeration and a primary treatment consisting of grit and grease removal. The characteristics of the influent wastewater are purely domestic. The plant is designed for 1216 population equivalents and at present 1160 population equivalents are connected. 

The aims were to evaluate the nutrient reduction, analyse whether biological phosphorus removal called Bio-P could be possible and to give suggestions for possible upgrades and improvements of the plant. It was done by constructing a nitrogen and phosphorus mass balance. Also, analyses were performed to assess the nitrification rate, measure the amount of volatile fatty acids in the influent and basic parameters such as dissolved oxygen, pH, mixed liquor suspended solids and aerobic sludge age. Samples were taken three times a week during a five-week period starting from the 21st of March 2016. 

The analyses showed that organic matter, measured as BOD and COD, were satisfactorily reduced. The nitrogen mass balances showed that nitrification and denitrification occurred, however the processes were uneven and not reliable. The results also showed that both the measured maximum and full-scale nitrification rate were very low which probably was due to low oxygen concentration and pH-levels in the aerobic tank. The mixed liquor suspended solids concentration and the aerobic sludge age was found to be enough for the bacteria to carry out the nitrification process, assimilate nutrients and for BOD-reduction.

The phosphorus mass balances showed that more phosphorus than expected was removed from the wastewater treatment plant; there was high phosphorus content in the sludge. The high removal may be due to Bio-P. Furthermore, investigations showed that there were enough volatile fatty acids in the wastewater to obtain Bio-P. If the characteristics of the wastewater are similar at other places, Bio-P could be an option for the future at wastewater treatment plants in Malaysia.

In order to upgrade the plant, calculations were made to evaluate if the size of the tank used for biological treatment is sufficient for nitrification and if there is space to incorporate an anoxic tank in order to get a predenitrification treatment. The results showed that with an expected nitrification and denitrification rate at the wastewater treatment plant the present volume is large enough for a pre-denitrification process. One of the main improvements that could be made at the wastewater treatment plant is to increase the nitrification rate by improving the aeration.},
  author       = {Ingvar-Nilsson, Caroline and Forså, Naima},
  keyword      = {Nutrients,Nitrogen,Extended Aeration,Nitrification rate,Phosphorus,Volatile Fatty Acids,Activated Sludge,Bio-P,water engineering,environmental engineering,vattenförsörjningsteknik,avloppsteknik},
  language     = {eng},
  note         = {Student Paper},
  title        = {Evaluation of an Extended Aeration System for Nutrient Removal, A Case Study of a Wastewater Treatment Plant in Kulai, Johor Baharu, Malaysia},
  year         = {2016},
}