Hybrid process for the purification of water contaminated with nitrites: Ion exchange plus catalytic reduction

Water polluted with nitrites represents a big risk to human health. In this work, palladium supported on macroporous anionic exchange resin was used in the catalytic nitrite reduction. This process is compared with the traditional ion exchange procedure using the same catalytic resin. Both, the resin and the catalyst behaviour were evaluated in a fix-bed reactor, feeding water containing nitrites and other competitor ions, such as sulphate, bicarbonate, and chlorides, and adjusting the pH with carbon dioxide. When feeding water containing only nitrites, it was observed that the catalytic reduction makes it possible to treat 55% more water than when using the ion exchange process, at the same level of nitrites elimination. Moreover, in steady state it was possible to obtain a nitrite conversion to nitrogen of 54% with high selectivity, obtaining an ammonium concentration lower than 0.2 mg/L. In the case of having other ions present in the system, both the conversion and the selectivity decreased. A regeneration strategy is also developed, using a very low hydrogen flow rate at atmospheric pressure and room temperature. This treatment leads to the reduction of more than 99% of the nitrites present in the contaminated water. The catalyst was used in several consecutive cycles maintaining a very good performance, even in the presence of competitor ions. The process was scaled up to a pilot level obtaining identical results.Fil: Mendow, Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; ArgentinaFil: Grosso, César L.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; ArgentinaFil: Sánchez, Agustina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; ArgentinaFil: Querini, Carlos Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; Argentin

Studies on the Removal of Sulfides from Wastewater

In the present work a thorough and systematic study has been made on the removal of sulfides by oxidation and precipitation methods. Both synthetically prepared sulfide solution and industrial waste water sample containing sulfide were treated by this method in the present investigations. Iodometric and spectrophotometeric methods were used for the analysis of sulfide and sulfur bearing other radicals. The treatment was carried out by aeration in the presence of UV light, oxidation by hydrogen peroxide in the presence of ferric oxide catalyst, precipitation using iron salts followed by aeration and aeration in the presence of ultrasonic vibration. Aeration in the presence of UV light was found to be very effective for the removal of sulfide. The effects of sulfide concentration and partial pressure of oxygen on the kinetics of oxidation of sulfide under specific UV light intensity was investigated. Sulfide oxidation was found to be faster at higher UV light intensity. The catalyst synthesized for the oxidation of sulfide was analyzed by XRD, FT-IR, SEM and EDX. The precipitate formed in the treatment process was also analyzed following the above mentioned techniques. SEM analysis of ferric oxide synthesized by sol-gel technique revealed that the average particle size of the sample was less than 200nm. The XRD picture of the catalyst reveals that the presence of non-stiochiometric ferric oxide appears as a major crystalline phase. In the FT-IR spectra of the catalyst sample stretching vibration of FE-O was observed in different regions. Oxidation of sulfide by hydrogen peroxide in the presence of synthesized ferric oxide catalyst was also found to be very effective. The effects of sulfide concentration, catalyst loading, hydrogen peroxide dosing and temperature were investigated on the kinetics of sulfide oxidation. Sulfide oxidation by hydrogen peroxide in the presence of catalyst was found to be faster with the increase in temperature. Before oxidation initially the sulfide solution was highly alkaline (pH =11-12) and during oxidation the solution became almost neutral (pH=7-8). It was observed that by precipitation more than 70% of sulfide was removed from the wastewater. Complete removal of sulfide was achieved by aeration in the presence of precipitate formed. From the SEM picture of the precipitate formed no distinct or definite size of the particle was observed. Average particle size of the precipitate was found to be 500nm. From the EDX analysis of the precipitate, it was confirmed that Fe and S were the major elements present in the sample. Some amount of Na and Cl were also observed in the sample. Aeration in the presence of ultrasonic vibration has also been carried out for the removal of sulfide. The effects of air flow rate and sulfide concentration were investigated on the kinetics of sulfide oxidation. Oxidation was carried out at different ultrasonic vibration frequencies. Rate of sulfide oxidation was found faster at higher air flow rate and sulfide concentration. The results of this study are expected to be useful for the assessment of different alternatives for the removal of sulfide as well as for actual remediation of sulfidic wastewater in chemical and allied industries

Treatment of municipal solid waste landfill leachate by use of combined biological, physical and photochemical processes

The purpose of this work was to study the treatment of a leachate coming from the municipal solid waste landfill of Astana (Kazakhstan). Physical (striping and adsorption), biological and photochemical processes were applied separately or in combination, and the treatment efficiency was attended in terms of carbon and nitrogen removal. The leachate carbon was by 45%–60% inorganic while nitrogen was almost 100% inorganic in the form of ammonia. The results showed that inorganic carbon and ammonia can be almost entirely removed by air stripping at pH = 7 and pH = 12, respectively. The removal of organic carbon by stripping alone was lower than 4% but combined to adsorption reached 20%, and to biological treatment 30%. The removal of organic carbon by photochemical oxidation alone was 43%. The combination of stripping, adsorption and biological treatment resulted in 37% organic carbon and with the addition of photochemical oxidation step the removal was increased to 59%. In overall, total carbon removal reached 85% and total nitrogen removal almost 100%. The results showed that the decomposition of landfill leachate carbon is a challenging task requiring a combination of processes. On the contrary, as almost all nitrogen is inorganic, air stripping at elevated pH alone can sufficiently eliminate it

Simultaneous Nitrate And Perchlorate Reduction From Drinking Water By Elemental Sulfur-based Autotrophic And Mixotrophic Denitrification Processes

Tez (Doktora) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2016Thesis (PhD) -- İstanbul Technical University, Institute of Science and Technology, 2016Perklorat (ClO4-), perklorik asitten elde edilen tuzlardır. Doğal ve antropojenik kaynaklardan içme sularına karışabilen perklorat, hava yastığı, havai fişek gibi bazı ürünlerde, füze – roket gibi askeri silahlarda ve bazı ilaç endüstrilerinde (hipertiroidizm tedavisinde) kullanılmaktadır. Perklorat, doğal yollardan ise atmosferde ozon ile klor gazlarının reaksiyonu neticesinde oluşmaktadır. Ayrıca ClO4- kurak bölgelerde bulunan nitrat yataklarında da bulunabilmektedir (Atacama Çölü/Şili). Bu bölgelerdeki nitratın gübre olarak kullanılmasıyla ClO4- yeraltı sularında nitrat ile birlikte bulunabilmektedir. Amonyum perklorat, sudaki yüksek çözünürlüğü ve düşük adsorpsiyon eğilimi nedeniyle içme sularına kolaylıkla karışabilmektedir. Perklorat, tiroit bezlerinin iyot bağlamasını engelleyerek vücuttaki tiroit hormonlarının (triiyodotironin-T3 ve tiroksin-T4) konsantrasyonunu düşürmektedir. Bu hormonlar yetişkinlerde bazal metabolizmayı, çocuklarda ise büyüme ve gelişmeyi düzenlerler. Bu nedenle içme sularında perklorat varlığı, bazal metabolizmaya bağlı birçok hastalığı tetiklemektedir. İçme sularından perklorat giderilmesinde kullanılan mevcut yöntemler giderim ve parçalama olarak ikiye ayrılmaktadır. Giderim yöntemleri, iyon değişimi, membran filtrasyonu ve adsorpsiyon iken, parçalama yöntemleri kimyasal, elektrokimyasal ve biyolojik indirgemedir. Giderim yöntemleri, ilave kimyasal ihtiyaçları, yüksek maliyetleri ve başka kirleticilerin ortamda bulunması durumunda düşük verim göstermelerinin yanında deşarj edilmesi gereken konsantre atıksu oluşturmaları gibi ciddi dezavantajlara sahiptirler. Parçalama yöntemlerinde ise biyolojik indirgeme, yüksek reaksiyon hızı, pahalı katalizörlere ya da kimyasallara ihtiyaç duymaması gibi nedenlerle en çok kullanılan yöntemdir. Birçok çalışmada ClO4- biyolojik olarak başarılı bir şekilde zararsız CI- iyonununa indirgenmiştir. Ülkemizde yaygın olarak bulunan konvansiyonel içme suyu arıtma prosesleri perklorat gideriminde etkili değildir. Düşük konsantrasyonlardaki perklorat ölçümü son on yılda gelişen analitik yöntemlerle mümkün olmuştur. Buna bağlı olarak başta ABD olmak üzere birçok ülkede içme sularında perklorat varlığı tespit edilmiştir. Ancak perklorat henüz Dünya Sağlık Örgütü (WHO), Avrupa Birliği, TS266 (insani tüketim amaçlı sular yönetmeliği) ve EPA'ya ait içme suyu standartlarında yer almamaktadır. bu ABD'de bulunan bazı eyaletler nedenle kendilerine ait standartları belirlerken (Arizona, 14 µg/L; Massachusetts, 2 µg/L; Nevada, 18 µg/L), EPA geçici limiti 15 µg/L olarak bildirmiştir. Nitrat, yüzeysel ve yeraltı sularında en çok karşılaşılan kirleticilerden biri olup, en önemli kaynakları tarımsal gübre kullanımı ve ileri arıtma yapılmadan deşarj edilen evsel ve endüstriyel nitelikli atıksulardır. TS 266’ya göre içme suyunda nitrat ve nitrit için sınır değerler sırasıyla 11,3 mg NO3--N/L ve 0,15 mg NO2--N/L’dir. Birçok yeraltı suyunda nitrat ve perklorat birlikte bulunabilmektedir. Dolayısıyla eşzamanlı olarak nitrat ve perklorat giderimi yapabilen biyolojik sistemlerin geliştirilmesine ihtiyaç duyulmaktadır. Son zamanlarda, içme sularından nitrat giderimi için ototrofik biyolojik denitrifikasyon prosesleri üzerine yoğun çalışmalar yapılmaktadır. Kükürt bazlı ototrofik denitrifikasyon prosesinde (SLAD: sulfur-limestone autotrophic denitrification) Thiobacillus denitrificans ve Thiomicrospira denitrican gibi türler görev alarak, kükürtü elektron verici, nitrat ve nitriti de elektron alıcı olarak kullanırlar. Proses sonunda kükürt sülfata, nitrat ise azot gazına dönüşür. Reaksiyon basit olarak aşağıda gösterilmiş olup, karbon kaynağı olarak CO2 kullanılmaktadır. 55S0+50NO3-+38H2O+20CO2+4NH4+ → 4C5H7O2N+55SO42-+25N2+64H+ (1) Sülfür bazlı ototrofik denitrifikasyon sisteminin birçok avantajı olmasına rağmen, esas dezavantajları sülfat ve asidite üretmesidir. Fakat heterotrofik denitrifikasyonda sülfat üretilmezken indirgenen g NO3--N başına 3.57 g CaCO3 üretilir. NO3-+1.08CH3OH+0.24H2CO3 → 0.056C5H7NO2+0.47N2+1.68H2O+HCO3- (2) Heterotrofik süreçlerde ise sülfat üretimi ve pH’da düşüş olmamasına rağmen, elektron kaynağının net ayarlanması esas dezavantajdır. Yüksek organik madde eklenmesi çıkışta kalıntı organik madde kalmasına sebep olabilirken, düşük organik madde yüklenmesi de çıkış suyunda nitrit gözlemlenmesine sebep olabilir. Bu nedenle, heterotrofik ve ototrofik süreçlerin kombinasyonu ile oluşturulan mixotrofik sistemler ile çıkış sülfat, organik kalıntı riski ve pH sorunu kontrol altına alınabilinir. İlave olarak hem nitrat hem de perklorat, ototrofik süreçlere nazaran daha yüksek seviyelerde indirgenebilir. Bu bağlamda bu tezin amaçları (1) içme sularından nitrat ve perkloratın birlikte giderimi için kükürt bazlı ototrofik denitrifikasyon süreçlerinin incelenmesi, (2) her iki anyonun metanol bazlı heterotrofik süreçlerde giderilmesi ve bu sürecin ototrofik sistemler ile mukayesesi. (3) metanolün ototrofik reaktöre eklenerek miksotrofik bir süreç oluşturulması ve avantajlarının belirlenmesi, (4) hem heterotrofik hem de ototrofik süreçlerin daha iyi izlenebilmesi için heterotrofik – ototrofik bir sıralı sistemin incelenmesi ve (5) Reaktörlerdeki baskın mikrobiyal kominitenin tespitidir. İlave olarak ototrofik reaktörlerde farklı alkalinite kaynakları kullanılarak bunun giderim verimine olası etkisi araştırılmıştır. Bu tez projesinde, 2 adet ototrofik ve 1 adet heterotrofik reaktör 100 den fazla gün boyunca işletilmiştir. Miksotrofik reaktör 174 gün, heterotrofik – ototrofik sıralı sistem ise 100 gün boyunca işletilmiştir. Ek olarak nitrat kirliliği bulunan bir gerçek yeraltı suyunun arıtılabilirliği 7 günlük bir periyotta sıralı sistemde test edilmiştir. Nitrat ve perkloratın giderim mekanizmalarının belirlenebilmesi içinde 90 saatlik bir kesikli test yapılmıştır. Son olarak baskın kominite yapılarının belirlenmesi için ise moleküler teknikler kullanılmıştır. Çalışmada ilk ototrofik reaktör elementel kükürt ve kireçtaşı partikülleri ile doldurulmuştur. Giriş suyu 25 mg NO3--N/L ve çeşitli konsantrasyonlarda (50-1000 µg/L) perklorat içermiştir. Test edilen tüm koşullarda nitrat tamamen giderilmiştir. Yüksek seviyelerde perklorat indirgenmiş olmasına rağmen, çıkış suyunda 21.88–85 µg/L arasında değişen konsantrasyonlarda perklorat tespit edilmiştir. Perklorat 1000 µg/L‘den 53±21.36 µg/L’ye düşürülerek 2 saatlik HRT’de %95’lik bir giderim verimi sağlanmıştır. Her iki anyonun birlikte giderimi çıkış suyunda 227±30 mg SO42-/L oluşumuna sebep olmuştur. Ortalama giriş alkalinite konsantrasyonu 155±23 to 96±30 mg CaCO3/L seviyelerine inmiş ancak kireçtaşı sayesinde daha fazla düşme eğilimi göstermemiştir. İkinci ototrofik reaktörde, alkalinite kaynağının etkisinin kıyaslanabilmesi için NaHCO3 kullanılmıştır. Bu reaktörde de yüksek perklorat giderim verimi gözlenmiş ve perklorat 1000 µg/L ‘den 33.23±30.4 µg/L’ye indirgenmiştir. Giriş 25 mg NO3--N/L tamamen giderilmiştir. Bu ototrofik reaktöre ait çıkış sülfat konsantrasyonu tüm çalışma boyunca ortalama 259±87.70 mg/L’dir. Her iki ototrofik reaktör için maksimum nitrat giderim oranı 300 mg NO3--N/(L.d) 'dir. Heterotrofik reaktör ise hem perkloratı hemde nitratı test edilen tüm koşullarda tamamen giderirken 2 – 4 mg/L DOC çıkış suyunda tespit edilmiştir. 25 mg NO3--N/L and 1000 µg/L perkloratın tamamı miksotrofik reaktörde giderilmiş ve çıkış sülfat konsantrasyonu C/N oranının ayarlanması ile kontrol altında tutulmuştur. Miksotrofik reaktör 25 mg/L methanol eklenmesi ile sağlanmış ve giriş nitratın %53’ü heterotrofik proseste giderilmiştir. Bu sayede çıkış sülfat konsantrasyonu ototrofik kısma göre yarı yarıya azalmıştır. Çıkış DOC konsantrasyonuda 2 mg/L’nin altında gözlemlenmiştir. Son olarak heterotrofik ototrofik sıralı sitem her iki anyonun giderilmesi için araştırılmıştır. Heterotrofik çıkış suyu ototrofik reaktöre verilmiştir. Bu düzenekte 100 mg NO3--N/L and 1000 µg/L perklorat tamamen giderilmiştir. C/N oranı 1.24 ile 2.77 arasında tutulmuş ve çıkış sülfat konsantrasyonu içme suyu standart değeri olan 250 mg/L’nin altına indirilmiş, pH nötral seviyelerde kalmıştır.Perchlorate (ClO4-) is the salt derived from perchloric acid. Perchlorate, can contaminate drinking water sources via natural and anthropogenic sources. Perchlorate is used in products such as airbags, fireworks, military weapons (eg. Missiles and rockets) and by the pharmaceutical industries (eg. For the treatment of hyperthyroidism). It naturally forms from the chemical reaction between chlorine gas and ozone and can be found in nitrate deposits in arid regions such as the Atacama Desert in Chile. With the utilization of nitrates as fertilizer, perchlorate might be more commonly found in the groundwater together with nitrate. Due to the high solubility and low adsorption properties of ammonium perchlorate, it can easily reach sources of drinking water. Perchlorate blocks the iodine uptake by the thyroid, decreasing the thyroid hormone (triiodothyronine-T3 and thyroxine-T4) concentrations in the body. These hormones regulate basal metabolisms in adults and normal development processes in children. Therefore the presence of perchlorate in drinking water might contribute to the onset of a variety of basal metabolic disorders. Current remediation methods are classified into two sub-groups: removal or destruction. Some removal methods include ion exchange, membrane filtration and adsorption. Destruction methods involve chemical, electrochemical or biological reduction. Besides the additional chemical requirements for these reduction processes, these removal methods are costly, and have low efficiencies when other contaminants are present in the solution. Most seriously, this removal method leads to the discharge of concentrated brine. Regardless, biological reduction is the most common method, due to its fast reaction rate, and the fact that it does not require expensive catalyst or chemicals. In many studies, ClO4- is sucessfully biologically reduced to CI- ion. However, these widely used conventional drinking water treatment processes are not effective in the treatment of perchlorate. In the last decade it has become possible to detect low concentrations of perchlorate, due to improvements in the analytical methods used. Since then, the presence of perchlorate has been detected in the drinking water of many countries, especially in the USA. However, perchlorate is not listed as hazardous by the standards of the World Health Organization (WHO), the European Union, TS266 (regulations on water intended on human consumption), or the US-EPA. While some US states have already established standards (Arizona, 14 µg/L; Massachusetts, 2 µg/L; Nevada, 18 µg/L), an Interim Health Advisory Level of 15 µg/L has been released by the EPA. Nitrate is one of the most commonly encountered pollutant in surface and groundwater. The most important sources of nitrate in groundwater are nitrogen containing fertilizers and the release of improperly treated wastewater from industrial and domestic sources. According to TS266, the maximum allowed concentrations of NO3--N and NO2--N are 11.3 and 0.15 mg/L, respectively. Additionally, many sources of groundwater may be contaminated with both nitrate and ClO4-, necessitating the development of processes able to simultaneously remove nitrate and perchlorate. Recently, many studies on autotrophic denitrification processes have been conducted. In sulfur-based autotrophic process (SLAD: sulfur-limestone autotrophic denitrification) sulfur and nitrate are used as electron donors and acceptors, respectively. As a result, sulfur is oxidized to sulfate, and nitrate is reduced to nitrogen gas. The reaction is given below (Equation 1), and CO2 is used as a carbon source. 55S0+50 NO3-+38H2O+20CO2+4NH4+ → 4C5H7O2N+55SO42-+25N2+64H+ (1) Although sulfur-based autotrophic denitrification has several advantages, its not widely used due to sulfate and acid formation. In heterotrophic denitrification, however, sulfate is not produced and 3.57 g CaCO3 is formed per gram of NO3--N reduced (Equation 2). NO3-+1.08CH3OH+0.24H2CO3 → 0.056C5H7NO2+0.47N2+1.68H2O+HCO3- (2) Even though there is no sulfate formed and the pH decreases in heterotrophic processes, these processes are highly sensitive to the quantity of (organic) electron donors. For example addition of more organic compounds may lead to effluent that still contains those compounds; whereas, nitrite formation may be observed in the case of lower amount of organic supplementation. Therefore, mixotorophic processes, that combine heterotrophic and autotrophic denitrification, can be used to control the amount of sulfate formation, the pH and the risk of residual organic compounds. Additionally, both nitrate and perchlorate reduction could be achieved at higher rates compared to autotrophic processes. Therefore the aims of this thesis are: (1) evaluation of sulfur-based autotrophic denitrification processes for the simultaneous reduction of nitrate and perchlorate from drinking water; (2) simultaneous reduction of both oxianions by methanol-based heterotrophic processes; (3) stimulation of the mixotrophic process by addition of organic matters to autotrophic process for simultaneous nitrate and perchlorate reduction; (4) evaluation of heterotrophic-autotrophic sequential process for nitrate and perchlorate reduction and (5) the determination of microbial community in the bioreactors under varying operational conditions. In addition to these aims, the effect of different alkalinity sources on autotrophic reactors was investigated. For this thesis project, two autotrophic, and one heterotrophic reactors were operated for more than 100 days. The mixotrophic reactor and the heterotrophic-autotrophic sequential system were operated for 174 and 100 days, respectively. Real groundwater polluted with nitrate was supplied to the sequential system for a 7 day period. To identify the nitrate and perchlorate removal mechanism, batch tests were conducted for 90 hours. The dominant microbial community was determined using molecular tools. The first autotrophic reactor was filled with elemental sulfur and limestone particles. The feed contained 25 mg NO3--N /L and various concentrations of perchlorate (50-1000 µg/L). Complete nitrate reduction was achieved in all tested conditions. Although high perchlorate removals were attained, perchlorate was always detected in the effluent; the concentrations varied from 21.88–85 µg/L depending on the perchlorate and nitrate loadings. Perchlorate was reduced from 1000 µg/L to 53±21.36 µg/L, corresponding to around 95% reduction with an HRT of 2 h. Simultaneous reduction of both anions produced sulfate in the effluent with 227±30 mg SO42-/L. The average influent alkalinity concentration was decreased from 155±23 to 96±30 mg CaCO3/L but not below this threshold because of the limestone. In the second autotrophic reactor, NaHCO3 was added to compare the effect of alkalinity sources. This reactor also highly reduced perchlorate and decreased perchlorate from 1000 µg/L to 33.23±30.4 µg/L. The influent nitrate concentration of 25 mg NO3--N/L was completely reduced. The effluent sulfate concentration of the autotrophic reactor averaged 259±87.70 mg/L throughout the study. For autotrophic reactors the maximum reduction rate of nitrate was 300 mg NO3--N/(L.d). The heterotrophic process reduced nitrate and perchlorate completely in all tested conditions (i.e., 25 mg NO3--N/L and 50-1000 µg ClO4-/L). However, 2 – 4 mg/L DOC was detected in the effluent. The complete reduction of 25 mg NO3--N/L and 1000 µg/L perchlorate was also accomplished in mixotrophic reactor and the effluent sulfate concentration was controlled by adjusting the C/N ratio in the influent. Mixotrophic denitrification was stimulated by the addition of 25 mg/L methanol. Fifty-three percent, of influent nitrate was reduced by heterotrophic process, which decreased the effluent sulfate concentration to half of the autotrophic counterpart. Effluent DOC concentrations were below 2 mg/L. Lastly a heterotrophic-autotrophic sequential system was investigated for the reduction of both anions. Heterotrophic effluent was pumped to autotrophic reactor. In this configuration, nitrate and perchlorate were reduced completely with maximum initial concentrations of 100 mg NO3--N/L and 1000 µg/L respectively. The C/N ratio varied between 1.24 and 2.77 throughout the study, effluent sulfate concentration was below the drinking water standard of 250 mg/L and the pH was neutral.DoktoraPh

Treatment of Industrial Effluents in a Bioreactor

The sources of occurrence of various pollutants from chemical process industries and there harmful effects have been highlighted. Typical composition of wastewater from various sources presented. The methods of treatment of wastewater briefly discussed. Special attention has been paid to the biological treatment mentioning the drawbacks of the traditional methods. The relative advantages of various modern bioreactors working on immobilization technique have been projected. A comparative picture with respect to various modern bioreactors has been presented and the uniqueness of the activated sludge and the fluidized bioreactors in the treatment of wastewater has been emphasized. Effluent was collected from Rourkela Steel Plant. BOD and COD were then done to measure the oxygen requirement of the effluent. It was then subjected to batch culturing at pH 6.5 to 7.5 and temperature 28 to 30ºC. COD was done on each day of batch culture. The gradual decrease of COD determines the viability of the microorganisms in the batch. After some days of batch culturing plastic beads were inserted so that adsorption over the plastic beads can occur and immobilization can take place. Then SEM was used to know the thickness of the microbes coated over the surface of the beads. Phenol is one of the most common contaminant, the methods of treatment of phenolic wastewater discussed emphasis given on the aerobic biological treatment. Special attention has been paid to the biological treatment. The relative advantages of various modern bioreactors working on immobilization technique have been projected

Characterization and evaluation of poplar and pine wood in twin biotrickling filters treating a mixture of NH3, H2S, butyric acid, and ethylmercaptan

Peer ReviewedPreprin

Biocatalytic membrane reactors

Biocatalytic membrane reactor

Comparative Study of a Novel Membrane Bioreactor System for Biological Nutrient Removal with Conventional Systems

This comparative study evaluated a novel membrane bioreactor (NMBR) for biological nutrient performance and membrane fouling with conventional BNR systems i.e. anaerobic/anoxic/aerobic (A O) process and University of Capetown (UCT) modified MBR process (UMBR). Comparison of the NMBR and A20 process, conducted at hydraulic retention time (HRT) of 8 hr and solids retention time (SRT) of 10 days using synthetic wastewater (SWW) and municipal wastewater (MWW), revealed that NMBR achieved lower effluent phosphorus than the A O with 0.2 vs 1.2 mg/L (SWW) and 0.8 vs 1 mg/L (MWW) as well as 20% lower sludge production. The study also substantiated that NMBR intermediate clarifier assisted chemical oxygen demand (COD), nitrogen, and P removals. Furthermore, the NMBR achieved 0.3 m/L lower effluent dissolved organic nitrogen (DON) than A20 and the DON reduction by membrane averaging 0.4 mg/L. The second comparative study with NMBR and UMBR process, tested at an HRT of 6 hr and SRT of 10 days using two different strength of MWW, indicated that effluent nitrate and P concentrations were lower in the NMBR than the UMBR by as much as 1 - 1.7 and 0.3 mg/L, respectively. Sludge P fractionation substantiated that poly-P content increased from 27-37% to 57-59% of the total phosphorus (TP) and P uptake by denitrifying phosphate accumulating organisms (DPAO) accounted for 37-40% of the total uptake in both systems. Both MBR systems showed similar membrane fouling trends with similar fouling rate of 4.4x1 O\u272 LMH/kPa-h. A statistical analysis confirmed that soluble microbial product impacts membrane fouling more significantly than floe size, the bound protein/total protein ratio and bound extracellular polymeric substance (EPS). The iii biofilm layer deposited on the membrane caused denitrification of as much as 1.5 mg N/L, which was primarily impacted by dissolved oxygen and transmembrane pressure, triggering membrane fouling. Another study of the impact of denitrification on membrane fouling propensity, using three different sludges i.e. conventional activated sludge (CAS), ordinary heterotrophic organisms (OHO) and DPAO, indicated that DPAO denitrification decreased cake layer resistance by 53% compared to an increase of 220 and 150% in CAS and OHO denitrification. The reduction in cake layer resistance for DPAO denitrification was associated with the increase in hydrophobicity and decrease in carbohydrate/protein ratio in bound EPS of DPAO after denitrification, with the reverse trend observed with CAS and OHO. Therefore, the contributions of this study are summarized as followings: 1. Identification of the role of the intermediate clarifier in the NMBR 2. Confirmation of the advantages & disadvantages of the NMBR relative to conventional systems 3. Extensive characterization of membrane foulants in BNR systems 4. Delineation of the fact that contrary to common belief, DPAO reduces foulin

Biocatalytic membrane reactors (BMR)

Biocatalytic membrane reactors (BMR