Study on Optimal Combination of Soft and Hard Packing Media in New Anaerobic Filter
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Based on the early works of winery waste water treatment with new anaerobic filter(AF).The effectiveness of six different new upflow anaerobic filters for treating the pretreatment winery waste water at 25 ℃ invariable temperatures was discussed.The devices have the same types of soft and hard packing media,but different media arrangement.The results showed that when influent concentration was about 3 000 mg/L,the best HRT was 24 h,and organic loading rate(OLR)was 3.75 kg COD/(m3·d).In that situation,with the soft media on the underneath,hard media was the top of the reactors;the optimal volume ratio of soft and hard packing media was 2∶1.The density of soft and hard packing media was 13.7 kg/m3,85 kg/m3 respectively.COD removing rate was 92.12%,suspended solids(SS) was 72.65%,the biogas recovery rate was 0.133 m3/kg CODremoved in this reactor.Keywords:
Winery
Anaerobic filter
Biogas
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In this paper coarse media filtration has been analysed as an alternative to the traditional settling in primary, secondary and tertiary treatment of wastewater. Various filter media configurations were evaluated for enhanced primary filtration. It was found that a dual media configuration based on Kaldnes biofilm media (K1 and K2modified) were most suitable when taking both separation efficiency as well as filter run time into consideration. SS removal efficiencies of around 75% were achieved in the dual Kaldnes primary filter at around 20 m/h without any chemical addition and around 85% at low dosage (1-2 mg/l) of a high MW cationic polymer FO4440SH. In the latter case COD was removed by around 70%. Further experiments were carried out on a multi-media Kaldnes-Filtralite-Sand (KFS) filter for enhanced primary treatment as well as for secondary filtration directly downstream of a high-rate moving bed biofilm reactor, resulting in an extremely compact secondary treatment process. The secondary KFS-filter gave SS-removal efficiencies around 90% (effluent SS < 15 mg/l) and filter run times of around 24 hrs at filtration rates of 10 m/h (sludge loading rates of around 1 kg /m2h) when a small dose (2 mg/l) of polymer was used. It is also demonstrated that the primary filter may also be utilised as a pre-denitrification reactor. A denitrification rate of 1.5 kg NO3-Nequiv./m3d was achieved when the filter was operated at a filtration rate of 5 m/h.
Filtration (mathematics)
Settling
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An effective lab-scale Anaerobic Filter Bed Baffled Reactor (AFBBR) was developed to treat food-processing wastewater. The effects of two factors, packing materials (gravel and plastic caps) and organic loading rates (1g/L-d to 8.5 g/L-d) on performance efficiency and biogas rate were investigated. Better performance efficiency was obtained using the plastic material as compared with that of gravel. The organic loading rate (OLR) when applied singly as a factor was best at 6.4 g/L-d. The combined effects of the two factors were markedly significant when AFBBR was operated at 4.2 g/L-d and 6.4 g/l-d for plastic and gravel, respectively. Key words: AFBBR, organic loading rate, packing material, removal efficiency
Anaerobic filter
Biogas
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Anaerobic filter
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To efficiently treat high concentration organic wastewater,we designed fixed carrier anaero-bic reactor R1 and R2.They are improvement of anaerobic baffle reactor(ABR).Its baffles were made from active carbon fiber,quick start-up of R1 and R2 is proceeded to treat molasses wastewater in a laboratory-scale.The hydraulic retention times(HRT) and organic loading rate(OLR) are important technical parameters which affect stable efficient operation and start-up of reactor.The results indicated when HRT is 2 d,reactors show the optimum operation.In the operation of 30 d,COD removal effi-ciency of R1 could reach the 84.88%,R2 could reach 81.72%.Biogas production rate increased from 0.35 L/(L.d) to 4.98 L/(L.d),with influent organic loading rate(OLR) raised from 1.25 kg/(m3.d) to 10 kg/(m3.d).In the two reactors,the pH value of effluent wastewater was between 6.7 to 7.6 and the pH value of influent wastewater was between 3.9 to 4.5.During the whole experimental period,the pH value of influent wastewater was not adjusted,which proved two reactors have strong ability to resist acid.The pH value of R1 fluctuated more gently.The reactors with less sludge losing and no clogging phenomenon showed the strong ability to treat acidic high concentration organic wastewater and to re-sist high shock loading during the whole running processes.
Hydraulic retention time
Clogging
Baffle
Biogas
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Aerobic granular sludge was cultivated in a sequencing batch reactor (SBR) in order to remove the organic matter present in winery wastewater. The formation of granules was performed using a synthetic substrate. The selection parameter was the settling time, as well as the alternation of feast-famine periods, the air velocity and the height/diameter ratio of the reactor. After 10 days of operation under these conditions, the first aggregates could be observed. Filamentous bacteria were still present in the reactor but they disappeared progressively. During the start-up, COD loading was increased from 2.7 to 22.5 kg COD/(m3 day) in order to obtain a feast period between 30 and 60 minutes. At this point, granules were quite round, with a particle diameter between 3.0 and 4.0 mm and an average density of 6 g L−1. After 120 days of operation, synthetic media was replaced by real winery wastewater, with a COD loading of 6 kg COD/(m3 day). The decrease of the organic load implied a reduction of the aggregate diameter and a density increase up to 13.2 g L−1. The effluent was free of organic matter and the solids concentration in the reactor reached 6 g VSS L−1.
Sequencing batch reactor
Settling
Winery
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A 9.8-L hybrid UASFB reactor, in which the lower half was occupied by a sludge blanket and the upper half by small floating polyethylene media, was evaluated using wine distillery vinasse as substrate. The reactor was operated for a total period of 232 days at 33 + 1°C. Continuous feeding of the reactor was started with an initial OLR of 2.9 g COD/L·d and then it was increased step wise to 19.5 g COD/L·d by increasing the feed COD, while maintaining a constant HRT (1.05 d). The reactor was equipped with a continuous internal recirculation system from top to the bottom at the rate of 9 L/h (upflow velocity = 0.83 m/h) upto day 159 and then it was reduced to about half on day 160 onwards. It was observed that the reduced recirculation rate did not affect the performance of the reactor with an average CODt and CODs removal efficiencies of 82 and 88%, respectively. A maximum gas production rate of 6.7 L CH4/Lreactor·d was achieved for the highest OLR applied. The specific activity analysis depicts that the activity of the attached biomass was more than 2 times higher than that of the granular sludge. The efficiency of liquid mixing was good through out this study. The packing medium had a dual role in the retention of the biomass inside the reactor: i.e. entrapment of biomass within the support and filtration of the granular biomass, preventing it from going out of the reactor. ADM1_10 model simulated well the dynamic evolutions of the main variables in the liquid as well as in the gas phases.
Vinasse
Hydraulic retention time
Hybrid reactor
Filtration (mathematics)
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In this research, possibility of reducing excess sludge production in wastewater treatment was investigated using a combined anaerobic and aerobic submerged biological filter in a pilot scale. The physical model designed, erected and operated consisted of two pipes of PVC type with 147mm and 237mm diameter used as aerobic and anaerobic filters, respectively. The effective height of porous media in these filters was 70cm. Two filters were connected to eachother in a series form and the resulted system was loaded using synthetic wastewater based on sucrose in the range of 1.91 to 30.61 kg/m3 for anaerobic filter and 1.133 to 53.017 kg/m3 for aerobic filter. For similar loadings, the aerobic filter showed efficiency of 1.8 times that of anaerobic filter in removal of soluble COD. Return of 100% flow from the aerobic filter to the anaerobic filter for 30kg/m3.d of organic loading increased the efficiencies of the anaerobic filter, the aerobic filter and the combined system as 17%, 14% and 15%, respectively and the effect of the return of the flow was more pronounced in smaller hydraulic retention times and larger loadings. 100% return of the flow reduced the yield coefficient for the whole system to 0.037 for 53 kg/m3 loading which is a suitable value with regard to the scheme and no use of chemical materials such as chlorine and ozone. This coefficient reached a value as small as 0.007 in common loadings (7.5kg/m3) for 100% return of the flow which is very close to zero. So, this method could be considered as a complete biological treatment with low excess sludge and could be assessed in full scale.
Anaerobic filter
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Inverse fluidization particles having specific gravity less than one are carried out in the reactor. The carrier particles chosen for this study was perlite having specific surface area of 7010m2/m3 and lowenergy requirements for fluidization. Before starting up the reactor physical properties of the carrier material were determined. 1mm diameter perlite particle is found to have a specific density of 295kg/m3. It was used for the treatment of distillery waste and performance studies were carried out for 85 days. Once the down flow anaerobic fluidized bed system reached the steady state, the organic load was increased step wise by reducing Hydraulic Retention Time (HRT) from2days to 0.19 day, while maintaining the constant feed of COD concentration.Most particles are covered with a thin biofilm of uniform thickness. This system achieved 87% COD removal at an Organic loading rate (OLR) of 35 kg of COD/m3/d.
Fluidization
Perlite
Hydraulic retention time
Particle (ecology)
Specific gravity
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The association of anaerobic process with membrane filtration in anaerobic membrane bioreactors (AnMBR) is a recent development in high rate anaerobic systems. This technology offers complete biomass retention regardless of settling properties, and enables the decoupling of hydraulic retention time (HRT) and solids retention time (SRT), with superior effluent qualities and small footprint areas. However, membrane fouling, an unavoidable circumstance, is still a crucial obstacle for AnMBR implementation. Gas-liquid two-phase air/gas sparging has been applied extensively for both aerobic membrane bioreactors (AeMBR) and AnMBR systems, but sparging for fouling control purposes is always the largest energy demand for MBRs operation. Hence, sophisticated hydrodynamics design is of prime importance to achieve effective exploitation of the energy input. The first stage of this study aimed to optimise two-phase flow hydrodynamic parameters such as gas flow rate, nozzle size and tank geometry for a gaslift-loop submerged flat-sheet MBR. The results showed that a O 3 mm nozzle sparger gave the largest bubble-membrane contact area. Threshold superficial air velocity was observed at 0.033 m s-1, while the increase in liquid upward flow velocity plateaued at a sparging rate of 6 Lmin-1. Adding suspended media is regarded as a promising strategy for membrane cleaning, with active adsorbents utilised most widely in either gas-sparged or fluidized bed MBRs. However, once the sorption capacity is diminished, then membrane scouring dominates. The introduction of non-adsorbent suspended particle has also been proposed. It has been reported that external irreversible fouling, which most of the time represents the major contributor to the total fouling, has been diminished effectively by the particles abrasion. This approach has successfully been operated with various AeMBR, while information on applying non-adsorbent suspended media in AnMBR, in which fouling phenomena are considered to be more intense when compared to AeMBR, is still very limited. Therefore, the overall aim of this research was to study the use of non-adsorbent particles coupled with conventional gas sparged AnMBR (GSAnMBR) functioning as a three-phase (solid/gas/liquid) flow for fouling mitigation and flux enhancement purposes, in an attempt to operate as a high-rate moving bed AnMBR (MBAnMBR) for dairy wastewater treatment. Trials were carried out to evaluate the feasibility and the related operational parameters of using non-adsorbent suspended particles associated with gas sparging in AnMBR. The experiments were carried out under simulated MBAnMBR conditions with low density polyethylene beads (SG 0.86 - 0.96, 2 - 3 mm apparent size) at different filling densities. Critical flux (Jcrit), supra-critical flux filtrations and resistance-in-series model experiments were carried out. The results demonstrated that Jcrit for 0, 11.1 and 22.2 % (v/v filling ratio) were 6, 7.5 and 9 L m-2 h-1 (LMH). Total filtration resistances (Rt) were 14.1 x 1012, 8.38 x1012 and 1.61 x 1012 m-1, of which cake resistance (Rc) represented the major contributor to Rt of 95.0, 92.3 and 62.1 %, respectively. This indicated that Rt has been decreased effectively by 40.6 - 88.6 % with the assistance of scouring particles. Long-term continuous operation for more than 300 days of 6.6 L lab-scale GSAnMBR and MBAnMBR was carried out under mesophilic conditions (37 °C) for synthetic dairy wastewater treatment. Systems were installed with a single A4 size flat sheet membrane (Kubota) made of chlorinated polyethylene with a nominal pore size of 0.4 m and total filtration area of 0.1 m2. Biogas from the reactor headspace was circulated at a rate of 5 Lmin-1 to create gas sparging for both reactors. Polyethylene glycol (PEG) granules, cylindrical in shape with the size and SG of 4 x 4 mm and 1.01 - 1.05 were applied as scouring media in MBAnMBR (10 % by volume fraction). Initial MLVSS was set at 4,500 mgL-1 and controlled to below 14,000 mg L-1. Net fluxes were initially set constant at 3.5 - 3.8 LMH resulting in HRT of 17 - 19 h and OLR were increased stepwise from 0.7 to 5.0 g CODremoved L-1 d-1 by influent concentration adjustment for the first 100 days of operation. Thereafter, influent concentration was fixed in the range of 3,600 - 3,900 mgL-1 until the end of experiments in which attainable OLRs were determined by achievable fluxes and SRTs were varied. The results illustrated that high total COD removal of 98 - 99 % could be achieved for both reactors under stable conditions corresponding to OLRs in range of 2.2 - 7.0 g CODremoved L-1 d-1 with F/M ratios of 0.25 - 0.65 g CODremoved g VSS d-1. Attainable net fluxes for long-term operation without rapid increases in TMP were at 2.8 and 3.7 LMH for GSAnMBR and MBAnMBR. This indicated that under the same given energy input for gas sparging, net flux could be enhanced by at least 24.3 % (even up to 35 %) with the assistance of scouring particles at a lower suction pressure. Additionally, MBAnMBR could be operated continuously for more than 300 days without backflushing or chemical cleaning. The higher VMP range of 0.63 - 2.30 L CH4 L-1 reactor day-1 for the MBAnMBR when compared to 0.68 - 1.86 L CH4 L-1 reactor day-1 for the GSAnMBR was due to higher OLRs causes by greater producible flux. A methane yield of 0.31- 0.32 L CH4 g-1 CODremoved which represents 90 - 92% of theoretical methane conversion was seen from both reactors. Similar observed biomass yields (Yobs) of 0.057 - 0.059 and 0.059 - 0.072 g VSS g-1 CODremoved were found for the GSAnMBR and MBAnMBR. Rc represents the major contributor to the Rt for both reactors. However, Rc in MBAnMBR is about 12-fold lower than in GSAnMBR with values of 4.8 x 1011 m-1 and 57.6 x 1011 m-1, respectively. Cake/gel forming could be alleviated effectively. Hence, particle addition could minimise the frequency of chemical cleaning, possibly prolonging membrane lifespan as well as reducing operational and maintenance expenses. No significant damage was observed on the membrane surface from using PEG granules as scouring agents under 5 L min-1 sparging after 308 days of operation.
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