CC BY
16
UDC 628.355.2
https://doi.org/10.15407/biotech11.02.057
APPLICATION OF AERATION-OXIDATIVE JET-LOOPED SETUP FOR BIOLOGICAL WASTEWATER TREATMENT
O. M. Obodovych1 L. A. Sablii2 V. V. Sydorenko1 M. S. Korenchuk2
institute of Engineering Thermophysics of the National Academy of Sciences of Ukraine, Kyiv 2National Technical University of Ukraine "Igor Sikorsky Kyiv Polytechnic Institute", Kyiv
E-mail: tdsittf@ukr.net
Received 27.12.2017
The purpose of the study was the design of an aerator-oxidizer and optimal parameters of its work to ensure the conditions of mixing and dissolution of oxygen, in which there is no disturbance of the state of activated sludge. The testing of the work of the aeration-oxidation setup of rotor type with the use of a sludge mixture with different design of aerator-oxidizers and in different operating modes was performed. The assessment of the effect of processing on the state of the activated sludge was carried out according to standard parameters: sludge index, chemical oxygen demand. In addition, the number and state of activated sludge organisms were evaluated. The results of qualitative and quantitative analysis of activated sludge before and after processing in the setup are presented. The parameters in which the activated sludge functions in satisfactory mode are revealed.
Key words: activated sludge, wastewater, aerator-oxidizer, sludge index.
The effectiveness of biological wastewater treatment depends on many factors: the dose of activated sludge, temperature, pH, daily wastewater consumption, etc. However, the most important and most energy-consuming is the degree of sewage saturation with oxygen. In the process of sewage aeration, pneumatic systems are widely used, which provide sufficient concentration of dissolved oxygen in the sludge mixture and its mixing. The search for ways to saturate the sludge mixture with air oxygen with reduced energy consumption remains an urgent problem [1, 2]. One of these methods is the use of hydromechanical systems of aeration. It is known that such aeration systems have lower specific energy expenditure compared with more commonly used pneumatic systems [3, 4]. Loop reactors with jet mixing are not widely used in biological treatment of sewage. However, it is known that such reactors create favorable conditions for the effective dissolution of oxygen in water. The induced air in the conditions of intense mixing and turbulent flows is dispersed in the form of microbubbles, greatly increasing the phase separation surface, which facilitates its dissolution [5]. However, the passage of sludge
mixture through a centrifugal pump and high velocities of passage through pipelines can cause mechanical damage to microorganisms of activated sludge [6, 7]. In addition, the sedimentation properties of activated sludge deteriorate as a result of mechanical damage to the activated sludge, which complicates its further separation [8].
The purpose of the study is to search for the design of an aerator-oxidizer and rational parameters of its work to ensure the mild conditions of oxygen mixing and dissolution, in which there is no violation of the state of activated sludge.
The objectives of the study are:
- estimation of the stability of sludge mixture parameters at different setup modes and aerator-oxidizer design;
- determination of the efficiency of contaminants removing by the criteria of chemical oxygen demand (COD).
Materials and Methods
The research was carried out on the basis of the experimental aeration-oxidative jet-looped setup at the Institute of Engineering
Thermophysics of the National academy of sciences of Ukraine (Fig. 1). Oxygen saturation of the treated medium and its mixing takes place in the aerator-oxidizer, which is rotary-pulsating apparatus (RPA). The research was carried out using two aerator-oxidizers of different design.
The working volume of the first aerator-oxidizer is 0.0014 m3. The main element of this device is the rotary-pulsating knot (RPK1), which consists of two rotors, connected in a single rotor knot (RK), and stator. The rotors have the following design parameters: internal radius of a small rotor Rsr = 56 mm, of a large rotor Rlr = 65 mm; the dimensions of the slits a = 3 mm; height hsl = 5 mm; angle between them is 6°; number m = 60. The gap between the rotor and the stator in the RPK is 8 = 0.15 mm. Structural parameters of the stator are as follows: internal radius Rst = 61 mm; the dimensions of the slits a = 3 mm; height hsl = 5 mm; angle between them is 6°; number m = 60.
The second type of aerator-oxidizer, with a volume of 0.0014 m3, contains RPK2 consisting of one rotor and a stator. The structural parameters of the rotor are: internal radius Rint = 40 mm; external radius Rext = 70 mm. The rotor contains 12 round holes with a diameter dh = 12 mm. Structural parameters of the stator: internal radius Rstint = 70 mm;
external radius Rstext = 75 mm. The number of holes is 20. The gap between the rotor and the stator is 8 = 0.3 mm.
As a parameter characterizing the conditions of medium processing in the RPA and can serve for different structures of the RPA comparison, the rate of the flow shift was chosen, which is determined by the formula:
a- R i y =-, ^ , (1)
where a is the angular velocity of the rotor, s1; R is the radius of rotor, m; ц is the gap thickness between the cylinders, m.
In the work, the determination of the doses of activated sludge by dry substance a and volume V, and sludge index I were performed.
The dose of activated sludge was calculated by the formula:
a =
(m2 - ml )
1000, g/dm3
(2)
Determination of the dose of activated sludge by volume lie in gravity sedimentation of the sludge mixture (Vs = 200 cm3) for 30 min with subsequent determination of the volume Vsl, which takes the sludge after sedimentation, and recalculated to 1 dm3:
V = 1000, cm3 /dm3
(3)
Wastewater
to Collector
C
Fig. 1. Aaeration-oxidative jet-looped setup:
A — the chart; B — RPK 1; C — RPK 2. 1 — storage capacity with internal cylinder; 2 — aerator-oxidizer; 3 — damper; 4 — three-way valve; 5 — recirculation pipeline; 6 — two-way valve; 7 — engine; 8 — cooling shirt; 9 — flow meter; 10 — manometer; 11 — thermometer; 12 — air flow meter; MCU is a management and control unit
s
In order to determine the dose of activated sludge a, the sludge mixture of volume V = 50 cm3 was collected, which was filtered on a pre-dried and weighed paper filter "white tape" of mass m1 and dried to constant weight m2 at 105 °C for six hours.
The sludge index is defined as the ratio of activated sludge dose of volume V to its dose a of dry matter:
г V 3
I = —, cm3 / g a
(4)
Investigation of activated sludge was carried out using a trinocular microscope of XSP-139TP Ulab model, equipped with an eyepiece with an increase of x10 and lenses with magnifications of x10, x20 and x40. In addition, the Carl Zeiss Axio Imager microscope was used.
To calculate the number of groups of activated sludge organisms, the method of "Calibrated drop" [9] was used. A sample of 150 cm3 of sludge mixture was collected, 0.1 cm3 of fluid was collected from it after preliminary mixing with a micropipette, placed on object glass and covered with 18x18 mm cover glass. Three such specimens were made. In each specimen, the number of organisms was counted in 10 fields of vision under a microscope with an increase of x100. The number of organisms D in 1 cm3 of sludge mixture was determined by the formula:
D =
S ■ <
%-r2■p
-, cell/cm3,
(5)
where d is the number of organisms in one fi eld of view (the arithmetic mean of the examined fields of view); r is radius of field of view in mm; S is the area of cover glass in mm2; p is the volume of used liquid, cm3.
Active sludge for research was taken from the sludge chamber after the secondary settling stations of Bortnitskaya aeration station in Kyiv. It represents an association of
Fig. 2. Microphotography of activated sludge with magnification of x200
microorganisms such as bacteria, mushrooms, actinomycetes, diatoms, green microalgae, as well as protozoa and some multicellular animals (flagellates, sarcodes, infusoria, worms, rotifers, etc.). Microphotographs of activated sludge are shown in Fig. 2.
The studies were conducted in two replicates. In both samples, the sludge is moderately-laden, no filamentous bacteria, but infusoria of the genera: Paramecium, Vorticella, Epistylis, Euplotes; rotifers of the genera: Habrotrocha, Epipheres, Rotaria, Pleurotrocha are present. In the second sample, the estimated number of organisms was determined, where the number of infusoria was 3 335 individuals per cm3, and the number of rotifers — 205 individuals per cm3. The both samples of activated sludge parameters are presented in Table 1. For further investigation of the purification effect by the COD parameter, a new sample of activated sludge was selected: the dose of sludge in volume is 880 cm3/dm3. Sludge index is 110 cm3/g.
For a qualitative assessment of sewage pollution, a standard method for chemical oxygen demand determining for 2 hours was used — COD.
The volume of sludge mixture was 30 dm3 with a sludge concentration of 2.5 g/dm3, which was obtained by diluting the activated sludge with settled tap water (when evaluating the parameters of activated sludge in the first stage of the research) and with sewage (in determining the degree of sewage treatment) in the apparatus before the start of experiments.
Results and Discussion
Table 1 shows the initial parameters of activated sludge, which was selected for research conducting at Bortnitskaya aeration station.
The first 3 experiments were aimed at rational parameters of setup work and its design finding. The following two studies were conducted to assess the depth of sewage treatment by COD index.
The first study of the parameters of activated sludge in the aeration-oxidative jet-looped setup was carried out at a rate of flow shift of 112103 s1, which is minimal for this apparatus. The temperature of the sludge mixture was 21.7 °C. The treatment time was 40 minutes. Sampling was performed every 10 minutes. An aerator-oxidizer with RPKj was used. The results are presented in Table 2 and in Fig. 3.
Table 1. Parameters of activated sludge selected at Bortnitskaya aeration station
Samples №№ Dose of activated sludge, a, g/dm3 Average dose of activated sludge, aav, g/dm3 Dose of activated sludge 00 0 V, cm3/dm3 Average dose of activated sludge Va„, cm3/dm3 Sludge index, I, dm3/g
I II I II
1 8.28 8.46 8.37 925 935 930 111.11
2 7.3 8.54 7.92 950 960 955 120.58
Note: 1 and 2 are successive samples; I and II are parallel samples.
Table 2. Parameters of activated sludge after processing with a flow shift rate of 112103 s 1
Samples №№ Dose of activated sludge, a, g/dm3 Average dose of activated sludge, aav, g/dm3 Dose of activated sludge V, cm3/dm3 Average dose of activated sludge Vav, cm3/dm Sludge index, I, dm3/g
I II I II
C 0.8 0.74 0.77 60 65 62.5 81.17
4 0.68 0.74 0.71 60 65 62.5 88.02
Note: C — control, 4 — sample taken after 40 min of setup working; I and II are repeated experiments.
A B
Fig. 3. Microphotography of activated sludge with magnification of x200:
A — control; B — the 4th sample
A B
Fig. 4. Microphotography of activated sludge with magnification of x100:
A — control; B — the 4th sample
The second study of activated sludge in setup was carried out at a rate of flow shift of 140103 s1. The temperature of the sludge mixture was 21.7 °C. An aerator-oxidizer with RPK1 was used. Processing time was 40 minutes. Sampling was performed every 10 minutes. The results are presented in Table 3, in Fig. 4 and Fig. 5.
A B
Fig. 5. Microphotography of activated sludge with magnification of x400:
A — control; B — the 4th sample
The third study of activated sludge in the setup was carried out at a rate of flow shift of 70103 s1. The temperature of sludge mixture was 21.7 °C. An aerator-oxidizer with RPK2 was used. Processing time was 28 minutes. The results are presented in Fig. 6 and Fig. 7.
The following studies were conducted using an aerator-oxidizer with RPK2.
The fourth biological wastewater treatment experiment was conducted at a rate of flow shift of 70 103 s1. The temperature of the sludge mixture was 24 °C. Processing time was 4 hours. Sampling was carried out before the study, at the 2nd hour, at the 3rd hour and at its completion. The results are presented in Table 4.
The fifth experiment on biological wastewater treatment was carried out with a reduced rate of flow shift — 56103 s1. The temperature of the sludge mixture was 24 °C. Processing time was 4 hours. Sampling was carried out before the study, at the 2nd hour, at the 3rd hour and at its completion. The results are presented in Table 4.
3-1
Table 3. Parameters of activated sludge after processing with the rate of flow shift of 7010 s
Samples №№ Average dose of activated sludge Vav, cm3/dm3 Average dose of activated sludge, aav, g/dm3 Sludge index, I, dm3/g Time from the start of the setup working t, min
C 82.5 0.64 128.91 0
1 90 0.61 147.54 10
2 90 0.56 160.71 20
3 90 0.52 173.08 30
4 77.5 0.47 164.89 40
Note: see note to the Table 2.
Fig. 6. Microphotography of activated sludge with magnification of x400:
A — control; B is a sample
Fig. 7. Microphotography of activated sludge with increase of x400:
A — control; B is a sample
Studies performed using an aerator-oxidizer with RPK1; demonstrate the constancy of activated sludge parameters at a minimum angular rate of setup.
During the study of activated sludge at maximal angular rate, the destruction of activated sludge flakes and the death of eukaryotes were detected according to the
results of microscopy (Fig. 5, B and Fig. 6, B). Significant growth of sludge index was noticed (Table 3).
Thus, in the third study with the usage of aerator- oxidizer with RPK2, it was established that the parameters of activated sludge at maximum angular rate of the setup were unchanged.
Table 4. Effect of sewage treatment in the setup
Experiment Sample №№ Processing duration, t, h COD, mg O2/dm3
control 0 200
2 1 -
I 3 2 160
4 3 220
5 4 240
control 0 113
2 1 180
II 3 2 167
4 3 167
5 4 -
During the fourth study, the crushing of activated sludge flakes starting from the first hour of the experiment was observed. At the 3rd hour of the experiment, there was a complete destruction of activated sludge flakes and the death of infusoria and rotifers — the remnants of the outer shells of these organisms are present. Further destruction of particles in the sludge mixture has led to an increase of pollution by the index of COD.
During the fifth study, the sludge retained viability throughout the experiment, but still there was a crushing of activated sludge from the first hour of treatment, which also led to the re-contamination of sewage.
It should be noted that secondary contamination of sewage apparently was the result of a fairly harsh conditions of the experiment. Thus, when the rate of flow
REFERENCES
1. Sablii L. A., Bunchak O. M., Zhukova V. S., Rossinskyi V. M. Equipment and engineering in bioenergy and water treatment and safety management. Rivne. National University of Water and Environmental Engineering. 2016, 356 p. (In Ukrainian).
2. Sablii L. A. Physical, chemical and biological treatment of highly concentrated waste water. Rivne: National University of Water and Environmental Engineering. 2013, 291 p. (In Ukrainian).
3. Bloor J. C, Anderson G. K., Willey A. R. High rate aerobic treatment of brewery wastewater using the jet loop reactor. Wat. Res. 1995, 29 (5), 1217-1223.
4. Abdel-Aziz M. H, Amin N. K, El-Ashtouk-hy E. S. Z. Removal of heavy metals from aqueous solutions by liquid cation exchanger in a jet loop contactor. Hydrometallurgy. 2013, 137, 126-132.
shift was 70103 s-1 and the volume of sludge mixture was 30 dm3, the frequency of its passing through the slotted holes of RPK aerator-oxidizer was 240 times per hour, or four times per minute, that does not meet the actual processing on treatment facilities.
It is found that using the second option of aerator-oxidizer provides soft mixing and aeration mode of the mixture that does not lead to the destruction of sludge and significant changes in its parameters (sludge index, sludge flakes integrity, protozoa and multicellular animals by samples microscopy). Further research will be directed to study the dynamics of wastewater biological treatment, removal efficiency of organic pollution and rational parameters of the purification process finding.
5. Petruccioli M., Cardoso Duarte J., Eusebio A., Federici F. Aerobic treatment of winery wastewater using a jet-loop activated sludge reactor. Proc. Biochem. 2002, 37 (8), 821-829.
6. Park B., Hwang G, Haam S., Lee Ch., Ahn Ik-Sung, Lee K. Absorption of a volatile organic compound by a jet loop reactor with circulation of a surfactant solution: performance evaluation. J. Hazard. Mater., 2008, 153 (12), 735-741.
7. Eusebio A., Mateus M., Baeta-Hall L., Saa-gua M. C., Tenreiro N., Almeida-Vara E., Duarte J. C. Characterization of the microbial communities in jet-loop (jacto) reactors during aerobic olive oil wastewater treatment. Intern. Biodeterior. Biodegrad. 2007, 59 (3), 226-233.
8. Patil M. S., Usmani G. A. Laboratory scale study of activated sludge process in jet loop reactor for waste watertreatment. J. Engineer. Res. Applicat. 2014, 4 (5), 68-74.
9. Kutikova L. A. Fauna of aerotanks. Sankt-Peterburg: Nauka. 1984, 264 p. (In Russian).
ВИКОРИСТАННЯ АЕРАЦ1ЙНО-ОКИСНЮВАЛЬНО1 УСТАНОВКИ РОТОРНОГО ТИПУ ДЛЯ Б1ОЛОГ1ЧНОГО ОЧИЩЕННЯ СТ1ЧНИХ ВОД
О. М. Ободович1
Л. А. СаблЬй2 В. В. Сидоренко1 М. С. Коренчук2
Институт техшчно1 теплофiзики НАН Укра1ни, Ки1в 2Нащональний технiчний унiверситет Укра1ни «Ки1вський полггехшчний iнститут iMeHi 1горя Сшорського»
E-mail: tdsittf@ukr.net
Метою дослщження був пошук конструкцп аератора-окиснювача та оптимальних параме-трiв його роботи для забезпечення умов пере-мiшування та розчинення кисню, за яких не вщбуватиметься порушення стану активного мулу.
Проведено випробування роботи аерацш-но-окиснювально1 установки роторного типу з використанням мулово1 сумiшi з рiзними кон-струкщями аераторiв-окиснювачiв i за рiзними режимами роботи. Ощнювання впливу обробки на стан активного мулу здшснено за стандарт-ними показниками: муловий шдекс, хiмiчне споживання кисню. Також ощнено кiлькiсть i стан органiзмiв активного мулу. Наведено результати яшсного й шльшсного аналiзiв активного мулу до та тсля обробки в установщ. Виявлено параметри, за яких активний мул функщонуе в задов^ьному режимi.
Ключовi слова: активний мул, смчш води, аератор-окиснювач, муловий шдекс.
ИСПОЛЬЗОВАНИЕ АЭРАЦИОННО-ОКИСЛИТЕЛЬНОЙ УСТАНОВКИ
РОТОРНОГО ТИПА ДЛЯ БИОЛОГИЧЕСКОЙ ОЧИСТКИ СТОЧНЫХ ВОД
О. М. Ободович1
Л. А. Саблий2 В. В. Сидоренко1 М. С. Коренчук2
1Институт технической теплофизики НАН Украины, Киев 2Национальный технический университет Украины «Киевский политехнический институт имени Игоря Сикорского»
E-mail: tdsittf@ukr.net
Целью исследования был поиск конструкции аэратора-окислителя и оптимальных параметров его работы для обеспечения условий перемешивания и растворения кислорода, при которых не будет происходить нарушение состояния активного ила.
Проведены испытания работы аэрацион-но-окислительной установки роторного типа с использованием иловой смеси с различными конструкциями аэраторов-окислителей и в разных режимах работы. Оценку влияния обработки на состояние активного ила осуществляли по стандартным показателям: иловый индекс, химическое потребление кислорода. Также оценивали количество и состояние организмов активного ила. Приведены результаты качественного и количественного анализов активного ила до и после обработки в установке. Выявлены параметры, при которых активный ил функционирует в удовлетворительном режиме.
Ключевые слова: активный ил, сточные воды, аэратор-окислитель, иловый индекс.
