Öğütülmüş mutfak atığı içeren evsel atıksular için yüksek yüklü aktif çamur ve ozon oksidasyonu prosesi
High load activated sludge and ozone oxidation for domestic wastewater containing granulated kitchen waste
Yazar: İLKNUR SİNOP
Danışman: PROF. DR. İZZET ÖZTÜRK
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Çevre Mühendisliği Ana Bilim Dalı / Çevre Bilimleri ve Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2017
Konu: Çevre Mühendisliği = Environmental Engineering

Özet:
İSKİ Baltalimanı Atıksu Arıtma Tesisi'nde ön arıtmaya tabi tutulan atıksu, pilot ölçekli hızlı aktif çamur sisteminde arıtılmıştır. Doksan sekiz gün boyunca pilot ölçeli tesisten numuneler alınmış ve analizler yapılmıştır. Pilot tesis işletim süresi üç dönemde yürütülmüştür: İlk elli dört gün boyunca biyolojik reaktöre hem ön arıtmadan geçmiş olan atıksu hem de İTÜ yemekhanesinden alınan organik katı atıklar öğütülerek  beslenmiştir. İkinci dönemde ise otuz gün boyunca pilot tesise organik katı atık beslemesi yapılmamış, tesis sadece ön arıtmadan gelen atıksu ile hidrolik bekletme süresi bir saat olacak şekilde çalıştırılmıştır. Üçüncü dönemde ise pilot tesis on dört gün boyunca yine sadece ön arıtmadan gelen atıksu ile hidrolik bekletme süresi otuz dakika olacak şekilde işletilmiştir. Sözü edilen üç dönem için gerekli analizler yapılarak karşılaştırılmalar yapılmıştır.
İlk dönemde, öğütülmüş organik katı atık ve atıksu birleşimi olan akımda, atıksuda, deşarj suyunda, biyolojik çamurda ve geri devir çamurunda  AKM, UAKM, toplam KOİ, kolloidal KOİ, çözünmüş KOİ, TN, TP, TKM, UKM, ÇHİ, pH gibi kirletici parametreler incelenmiş ve organik katı atığın kirletici parametreler üzerinde ne kadar artışa sebep olduğuna bakılmıştır. Ayrıca çıkış suyuna ozonloma uygulanarak, deşarj suyu kalitesinin arttırılması hedeflenmiştir. Bu dönem boyunca tesisten her gün atıksu numuneleri alınmıştır. 
İkinci dönemde, atıksuda, çıkış suyunda, biyolojik çamurda ve geri devir çamurunda  AKM, UAKM, toplam KOİ, kolloidal KOİ, çözünmüş KOİ, TN, TP, TKM, UKM, ÇHİ, pH gibi kirletici parametreler incelenmiştir. Bu dönem boyunca tesis 1 saatlik hidrolik bekletme süresi ile çalıştırılmıştr. Ayrıca deşarj suyuna ozonloma uygulanarak, çıkış suyu kalitesinin arttırılması hedeflenmiştir. Bu dönemde tesisten gün aşırı numune alınarak analizler yapılmıştır.
 Üçüncü dönemde, atıksuda, çıkış suyunda, biyolojik çamurda ve geri devir çamurunda  AKM, UAKM, toplam KOİ, kolloidal KOİ, çözünmüş KOİ, TN, TP, TKM, UKM, ÇHİ, pH gibi kirletici parametreler incelenmiştir. Bu dönem boyunca tesis yarım saatlik hidrolik bekletme süresi ile çalıştırılmıştr. Ayrıca deşarj suyuna ozonloma uygulanarak, çıkış suyu kalitesinin arttırılması hedeflenmiş, tesisten gün aşırı numune alınarak analizler yapılmıştır.
Her üç dönem için de yürütülen analizlerden elde edilen sonuçlar verilmiştir. Bu değerler  birbirleri ile karşılaştırılmıştır. Organik katı atık, atıksudaki toplam KOİ miktarını %13 oranında, çözünmüş KOİ'yi %11 oranında, kolloidal KOİ'yi %13 oranında arttırmıştır. Buna rağmen sistemin giderme veriminde çok ciddi bir düşüş olmamıştır. Öğütülmüş organik katı atık ve atıksuyun beraber beslendiği durumlarda toplam KOİ giderim verimi %36 , çözünmüş KOİ giderim verimi % 45 olmuştur. Bu sonuçlar, organik katı atığın evsel atıksu arıtma tesislerinde atıksu ile birlikte bertaraf edilebilmesinin mümkün olduğunu göstermektedir. 
Çıkış suyu kalitesinin arttırılması amacaıyla, pilot A reaktörü deşarj suyuna ozon oksidasyonu uygulanmıştır. İlk olarak sadece ozonlama yapılmış daha sonra ozon ve hidrojen peroksit (perokson) kullanılmıştır. Aynı numuneye, hem ozonloma hem peroksonloma yapılarak A prosesi sonrası ilave giderim verimleri karşılaştırılmıştır. Birinci dönemde, öğütülmüş organik katı atık ve atıksuyun sisteme beraber beslendiği durumda alınan numunede sadece ozonloma yapılması durumunda toplam KOİ giderim verimi % 57 iken , peroksonlama  ile  bu verim % 61 mertebesine yükselmiştir.İkinci dönemde alınan, sadece atıksu beslemesi yapılan sistemin hidrolik bekletme süresinin 1 saat olduğu durumda, alınan numunede ise sadece ozonlama yapılan durumda giderim verimi 41 iken, peroksonloma ile bu verim % 55 seviyelerine yükselmiştir. Üçüncü dönemde, sisteme sadece atıksu beslendiği ve sistemin hidrolik bekletme süresinin yarım saat olduğu durumda alınan numunede, sadece ozonloma yapılmasıı halinde giderim verimi % 35 iken , peroksonlama ile bu değer % 55'e yükselmiştir.

Abstract:
Wastewater treatment is one of the most important issues in environmental engineering. The increasing population and consequent high water consumption make this matterof greater concern. The world population is estimated to be 7.9 billion by 2020. This alone is proof that the need for water will seriously rise in the upcoming years. Along with the population increase industrial and agricultural requirements are expected to escalate as well. Thus, water resources must be protected and kept clean for the sake of sustainability. At this point, the prominence of wastewater treatment emerges. Domestic and industrial wastewater, and leachate are major hazards for clean water resources; therefore they need to be treated in the best available way before discharging into receiving bodies. 
Many different technologies are used in wastewater treatment throughout the world. The most common wastewater treatment systems used in the recent years are activated sludge systems. These systems are available in various processes, such as completely mix, dispersed piston flow, stepped feed and extended geretad  sludge. In this study,  a two stage activated sludge system has been choosen;this system often regarded as the 'AB Process' as a high rate activated sludge system, removes COD, nutrients and other pollutants. It also provides biological treatment of highly polluted industrial wastewater succesfully. The system consists of a high-load Stage A (adsorption), and a low-load Stage B (biological oxidation), where Stage A operated at low requirement has 60-80% COD  removal efficiency, while Stage B is utilized for nutrient removal. The excess sludge coming from Stage A has a high biogas (biomethane) production potential. A-stage processes operated at solids retention times (SRT) less than about one day and the A-stage has also been used as a cost-effective biological buffer against nitrification inhibition at a plant with highly variable industrial inputs and has been used to successfully treat high-strength industrial streams to include textile dying, pulp and paper mill, and leather tanning The purpose of selecting the AB process in this study is to be able to operate with lower installation and operating costs compared to classical two-stage systems, while the space required for installation of AB Process is smeller as well. 
Within the scope of the thesis, only Stage A of the AB process has been investigated. The pilot plant choosen for this purpose, has Stage A component, a settling tank and a sludge digester located within the Baltalimanı Wastewater Treatment Plant (WWTP) in İstanbul. The inlet wastewater undergoes preliminary treatment at the existing full scale WWTP and fully treated. Here, it is aimed to reduce the pollutant loads (COD, TSS, TP and TN) in the outlet of pilot plant settling tank. The studies were carried out in 3 periods; organic kitchen wastes passing from the grinders and wastewater from the pre-treatment were fed together in the first period. In the second period, only the wastewater was fed and the hydraulic retention time has been selected as 1 hour. Subsequently, only the wastewater was fed again and the hydraulic retention time was taken as 30 minutes in the final period. The plant has been fed with organic kitchen wastes from the dining hall/cafeteria of Istanbul Technical University (ITU). Thus, a different perspective has been introduced in solid waste management as well. Additionally, it is known that the VSS value in anaerobic digestion, increases in the feed sludge when kitchen grinders are used at domestic households. Higher amounts of biogas is produced  by anaerobic digester through this method. The excess sludge from the pilot plant has been diverted to the anaerobic digester. Finally, chemical post-oxidation was carried out in order to obtain a higher quality discharge.
In Turkey, solid wastes are usually disposed of at sanitary landfills. Organic wastes constitute 50-60% of the solid waste generated throughout the country. However, these organic wastes can be utilized/disposed of in different ways rather than being sent to landfills. The most important step is to be able to collect organic solid wastes separately at source. This pilot test method allows organic solid wastes to be collected separately, resulting in cost reduction for collection and disposal. Within the scope of the project, it is planned that organic kitchen wastes are to be  separated at households, and fed to sewerage through the kitchen grinders (mills). This will also reduce the amount of waste per capita, and help fulfill the European Union's "EU Directive on Landfilling of Waste" (1993/31).
It is aimed to obtain methane gas by mesophilic digestion of the sludge from the A process in the sludge digester. In the high-loaded Stage-A of the AB process, adsorbed organic matter can be converted into highly efficient biogas in anaerobic digesters. This methane gas will be utilized for obtaining energy for the plant, thus the plant can be operated as an energy-neutral system.
Finally, chemical oxidation was applied to the outlet of the sedimentation tank in order to increase the quality of the discharge. Ozonation and peroxidation, which are the most commonly used methods for wastewater oxidation, have been utilized in the study. Ozone has been used as an oxidant in Europe for many years with the advantage of complete oxidization of pollutants that cause odor, color, and problems in water. In addition, compounds such as COX, H2O, which are completely harmless in the water, do not leave any undesirable residues during oxidation. The ozone used in the project has been obtained from oxygen in the laboratory environment. Both ozonation and peroxidation were performed on the samples taken for all three periods, and the results were compared respectively.
The samples were taken at pre-specified points for a period of 98 days in the study. During the first period, 54 days samples were taken from; the wastewater feed point, the point where milled organic solid wastes were diluted and fed, the aeration tank, the sedimentation tank, and the return sludge. From these samples, wastewater feed, organic waste feed and discharge water samples; pH, total COD, colloidal COD, dissolved COD, TSS, VSS, NH4-N, TN and TP, PSD and Zeta Potential analysis were performed. The TSS and VSS parameters were also examined in the sample taken from the point where the organic solid waste is diluted and fed. pH, SVI, TSS and VSS experiments were performed on the sample taken from the aeration tank (A Stage). The pH, TSS, VSS, TS and VS tests were carried out on the sludge sample taken from the recycle line. The samples in the second period were obtained from the wastewater feed point, the aeration tank, the sedimentation tank outlet, and return sludge. In the second period, a sample was taken every two days and the facility was operated in this manner for as long as 30 days. In the final period, the sampling points and schedule of the second period were kept the same, while the plant was operated for 14 days. 
The analysis of the parameters has been conducted, and the treatment efficiency is calculated in the monitored system. In addition, sludge age, organic loading rate, F/M ratio and, return sludge ratio were calculated separately for each period.
For the first period, total COD removal efficiency was 37 %. Average wastewater flow for the first period was 95,04 m3/day, sludge recycle amount was 8,60 m3/day, hydraulic retention time was 1,01 hours, sludge age was 0,53 days, organic loading rate was 11,30 kg COD m3 day and the F/M ratio was calculated as 18,36 kg COD/kg VSS day. In addition, the average temperature of the aeration tank is 25,07 °C, and the average dissolved oxygen amount of the aeration tank is 0,44 mg/L in this period.
In the second period, hydraulic retention time is the same as of the first period, but sludge age is 0,86 days. Removal efficiencies are higher than the first period with total COD removal efficiency. Flowrate is 97,74 m3/day for second period, sludge recycle amount 10,50 m3/day, organic loading rate 17,57 kg COD/m3 day, and the F/M ratio was calculated as 17,76 kg COD/kg VSS day. In addition, the average temperature of the aeration tank during this period is 24.56 °C, and the average dissolved oxygen amount of the pool is 0.35 mg/L.
For the third period, removal efficiency of total COD is  48.93 %.  Average wastewater flow for the third period is 175,10 m3/day, sludge recycle amount 19,59 m3/day, hydraulic retention time 0,55 hours, sludge age 0,15 days, organic loading rate 20,29 kg COD/m3day, and the F/M ratio 19.58 kg COD / kg VSS day. The average temperature of the ventilation pool during this period is 21.66 °C, and the average dissolved oxygen amount is 0.36 mg/L.
Finally, the examination revealed that that there was not a significant decrease in the removal efficiency when organic solid wastes were diluted and fed to the system combined with wastewater. It can be stated that it is not disadvantageous for organic solid wastes to be disposed of in domestic wastewater treatment systems. When the second and third periods are compared among themselves, it is observed that the efficiency of the system increases when the hydraulic retention time is 1 hour.
In order to increase the discharge quality of the sedimentation tank outlet, ozonation and peroxination were carried out by taking samples for the three periods. Different ozone doses were applied to the 1 liter sample from the discharge water for 15 minutes. The treatment yields were calculated by examining the analysis results.
After the ozonation of the sample taken in the first period; removal efficiencies were 57 % for total COD, 40 % for dissolved COD, 63 % for colloidal COD, 4 for NH4-N, 16 % for TN, 26 % for TP, respectively. After the peroxonation performed on the sample taken in the first period; removal efficiencies for total COD, dissolved COD, colloidal COD, NH4-N, TN, TP were 61 %, 54 % , 56 % , 9 % , 22 % , 29 % and 71 % respectively.
In the second period removal efficiencies were respectively 41 % for total COD, 2 % for dissolved COD, 11 % for colloidal COD, 8 % for NH4-N, 8 % for TN, 7 % for TP for ozonation. While after the peroxonation; removal efficiencies were 55 % for total COD, 22 % for dissolved COD, 39 % for colloidal COD, 19% for NH4-N, 22 % for TN and 8 % for TP, respectively.
After the ozonation of the sample taken in the third period; removal efficiencies were calculated as 34 % for total COD, 3 for NH4-N, 14 % for TN and 8 % for TP. The peroxonation resulted in removal efficiencies of 55 % for total COD, 10 % for dissolved COD, 12 % for colloidal COD, 13 %  for NH4-N, 21 % for TN and 11 % for TP respectively.
When ozonation and peroxonation (O3/H2O2) are compared, the removal efficiencies, and peroxidation yields were higher with peroxonation, and thus peroxone is concluded to be more a more suitable agent for oxidation.
It has been understood with regards to the A Process that its removal efficiency is comparable to conventional activated sludge systems while consuming less energy. Furthermore, the biogas obtained by feeding the treatment sludge from the Stage A into anaerobic digestion can meet the energy requirement of the plant. This ensures that the plant becomes an energy-neutral system.