Anaerobic Treatment Of Cheese Whey Research Articles

Organic loading rate effect on the acidogenesis of cheese whey: a comparison between UASB and SBR reactors

ABSTRACTVolatile fatty acids (VFA) production and degree of acidification (DA) were investigated in the anaerobic treatment of cheese whey by comparison of two processes: a continuous process using a laboratory upflow anaerobic sludge blanket (UASB) reactor and a discontinuous process using a sequencing batch reactor (SBR). The main purpose of this work was to study the organic loading rate (OLR) effect on the yield of VFA in two kinds of reactors. The predominant products in the acidogenic process in both reactors were: acetate, propionate, butyrate and valerate. The maximum DA obtained was 98% in an SBR at OLR of 2.7 g COD L−1 d−1, and 97% in the UASB at OLR at 15.1 g COD L−1 d−1. The results revealed that the UASB reactor was more efficient at a medium OLR with a higher VFA yield, while with the SBR reactor, the maximum acidification was obtained at a lower OLR with changes in the VFA profile at different OLRs applied.

Enhancement of Biogas Production by Using a Two-Stage Process for the Anaerobic Digestion of Cheese Whey

Cheese making companies have a specific product that is seasonally produced and, like most other agro-industries, generate wastewaters characterized by a high organic loading. Cheese whey is the most important waste stream produced having a high organic content (up to 70 g COD/L), which is highly biodegradable, and low alkalinity (50 meq/L). Cheese production industries worldwide generate more than 145 million tones of liquid whey per year. Because of these characteristics, cheese whey may cause serious environmental problems on the local municipal sewage treatment systems or water receptors if disposed untreated. Anaerobic digestion is a particularly attractive treatment solution for high strength wastewaters due to the operational economy and generation of biogas and therefore is considered as a promising solution for energy production from cheese whey, in this case. In this work, a comparative study between single and two-stage anaerobic treatment of cheese whey was conducted in order to enhance biogas production. Our experiments were carried out using one reactor for the single-stage process (operated at a HRT of 20 d), and two reactors connected in series, from which the first one was used for acidogenesis (operated at a HRT of 3 d) and the other for methanogenesis (operated at a HRT of 20 d). The single-stage process presented many operational problems, as a result of little or no buffering capacity of whey, which caused the pH of the anaerobic digester to drop drastically and the process being inhibited. This kind of inhibition proved to be irreversible and the digester was not able to recover even though it was operated batchwise and the value of the pH was restored to 7.0. On the contrary, the two-stage process exhibited a stable biogas production rate of 1.57 L/Lreactor/d with the composition of methane in the biogas reaching 54.3%. The dissolved COD and total carbon concentration removal was 70.5% and 77.2% respectively.

Continuous treatment of dairy effluent in a downflow anaerobic filter packed with slag grains: Reactor performance and kinetics

ABSTRACT A downflow anaerobic filter packed with blast-furnace slag (BFS) grains was evaluated for treating cheese whey, a high-strength dairy effluent. The reactor demonstrated effective and stable biomethanation of whey in continuous mode without pH control. The chemical oxygen demand (COD) removal remained at around 80%, with the reactor pH being maintained neutral without buffering, in the organic loading rate (OLR) range of 0.8–2.4 g COD/l∙d. Although the COD removal decreased down to below 60% at higher OLRs along with acid accumulation, the methane production rate continued to increase with increasing OLR. On the other hand, the methane yield was maintained at 0.28–0.34 l/g COD throughout the experiment. The substrate removal and methane production kinetics were successfully described by the modified Stover–Kincannon model. The overall results suggest that BFS grains could be used as economic filter media for anaerobic treatment of cheese whey and other easily acidifying waste streams.

Exergetic and economic analysis of a cheese whey wastewater anaerobic treatment plant with a cogeneration system

This paper investigates the extension of an existing steam production plant in order to cover both thermal and electrical needs of a factory. The plant uses biogas produced from cheese whey (CW) wastewater anaerobic digestion treatment. For this purpose a microturbine is chosen among the commercially available microturbines. The selection of the suitable microturbine for matching with the existing system is not a trivial task: the limitations (the amount of the biogas produced), the requirements (the amount of the steam produced) of the existing system, and the specifications of the microturbine by the manufacturer must be satisfied. The system considered was studied through the development of an appropriate simulation model validated with available data. Then an exergetic and economic analysis for the extended system was carried out. The results showed that the matching performance of the microturbine with the existing system has positive effects on the exergy efficiency of the plant as well as to the incomes and savings for the factory which are significantly increased compared to the existing ones. Thus, this study proves that the anaerobic treatment of CW is a sustainable way for the factory to treat the whey it produces.

Coupling digestion in a pilot-scale UASB reactor and electrochemical oxidation over BDD anode to treat diluted cheese whey.

The efficiency of the anaerobic treatment of cheese whey (CW) at mesophilic conditions was investigated. In addition, the applicability of electrochemical oxidation as an advanced post-treatment for the complete removal of chemical oxygen demand (COD) from the anaerobically treated cheese whey was evaluated. The diluted cheese whey, having a pH of 6.5 and a total COD of 6 g/L, was first treated in a 600-L, pilot-scale up-flow anaerobic sludge blanket (UASB) reactor. The UASB process, which was operated for 87 days at mesophilic conditions (32 ± 2 °C) at a hydraulic retention time (HRT) of 3 days, led to a COD removal efficiency between 66 and 97 %, while the particulate matter of the wastewater was effectively removed by entrapment in the sludge blanket of the reactor. When the anaerobic reactor effluent was post-treated over a boron-doped diamond (BDD) anode at 9 and 18 A and in the presence of NaCl as the supporting electrolyte, complete removal of COD was attained after 3-4 h of reaction. During electrochemical experiments, three groups of organochlorinated compounds, namely trihalomethanes (THMs), haloacetonitriles (HANs), and haloketons (HKs), as well as 1,2-dichloroethane (DCA) and chloropicrin were identified as by-products of the process; these, alongside free chlorine, are thought to increase the matrix ecotoxicity to Artemia salina.

Two-stage CSTR–UASB digestion enables superior and alkali addition-free cheese whey treatment

Different process configurations for the anaerobic treatment of cheese whey were comparably investigated under continuous operation. Three systems consisting of (i) a single-stage UASB (upflow anaerobic sludge bed) reactor, (ii) a CSTR (continuous stirred-tank reactor) coupled to a sedimentation tank and a subsequent UASB reactor and (iii) the same CSTR–UASB reactor scheme, although with biomass recirculation taking place from the sedimentation tank to the CSTR, were tested during three successive experimental periods (i.e. periods I, II and III, respectively). Acidifying biomass recirculation resulted in complete carbohydrate fermentation in the CSTR, while partial acidification occurred in the absence of biomass recycling. Fluorescent in situ hybridization (FISH) analysis revealed that acidifying biomass was dominated by bacteria rather than yeasts. The OLR (organic loading rate) in the UASB reactor highly correlated with the specific biogas production rate (p<0.01), although biogas composition differed significantly among the three periods. The enhanced acidification system was capable to ensure up to 90% COD (chemical oxygen demand) removal in the UASB reactor and optimum methane yield values (i.e. 0.37Nm3CH4kg−1CODrem). Moreover, recirculation of the acidifying biomass eliminated alkali addition under any OLR tested. Two-stage configurations has been proved superior in terms of process efficiency and methane recovery as compared to the single-stage system, while the enhanced acidification process resulted in optimum operational and performance features. A case study of a two-stage anaerobic digestion system for a small-to-medium size cheese production plant indicated a net profit of 0.94€m−3 CW from biogas production and valorization.

Biotechnological Utilization with a Focus on Anaerobic Treatment of Cheese Whey: Current Status and Prospects

Cheese whey utilization is of major concern nowadays. Its high organic matter content, in combination with the high volumes produced and limited treatment options make cheese whey a serious environmental problem. However, the potential production of biogas (methane), hydrogen or other marketable products with a simultaneous high COD reduction through appropriate treatment proves that cheese whey must be considered as an energy resource rather than a pollutant. The presence of biodegradable components in the cheese whey coupled with the advantages of anaerobic digestion processes over other treatment methods makes anaerobic digestion an attractive and suitable treatment option. This paper intends to review the most representative applications of anaerobic treatment of cheese whey currently being exploited and under research. Moreover, an effort has been made to categorize the common characteristics of the various research efforts and find a comparative basis, as far as their results are concerned. In addition, a number of dairy industries already using such anaerobic digestion systems are presented.

Anaerobic biotransformation and methane generation potential of cheese whey in batch and UASB reactors

Anaerobic treatability and methane generation potential of cheese whey were determined in batch reactors. Furthermore, the effect of nutrient and trace metal supplementation on the batch anaerobic treatment, and the high-rate anaerobic treatability of cheese whey in upflow anaerobic sludge blanket (UASB) reactors were investigated. To this purpose biochemical methane potential experiments were conducted and single- and two-stage UASB reactors with granular cultures were operated. In UASB experiments significance of process staging, operational parameters such as hydraulic retention time (HRT), influent chemical oxygen demand (COD) concentration and loading rate were also investigated. The results revealed that nutrient and trace metal supplementation is vital for the anaerobic treatment of cheese whey; the anaerobic methane generation for the cheese whey studied was found to be 424 ml CH 4/g COD (23.4 l CH 4/l cheese whey); undiluted cheese whey could be treated anaerobically at relatively short HRT values (2.06–4.95 days) without any significant stability problems; HRT values as low as 2–3 days can be used for the anaerobic treatment of cheese whey, with a COD removal efficiency of 95–97% at influent COD concentration of 42 700±141–55 100±283 mg/l.

Two-phase anaerobic treatment of cheese whey

Performance of two-phase anaerobic digestion of cheese whey was investigated in a system consisting of a continuous stirred tank reactor (CSTR) as the acidogenic reactor and an upflow anaerobic filter (UFAF) as the methanogenic reactor. The acidogenic reactor was operated at various hydraulic retention times (HRTs) between 18 hours and 4 days. The results showed that an optimum HRT for the acidogenic reactor with the same organic loading rate (OLR) between 0.5-2 g COD/MLSS day was 24 hours. At this retention time the acidification rate increased up to a maximum of 50%. Volatile fatty acids (VFAs) produced in the acidogenic reactor operating at an HRT of 24 hours were 52% acetic acid, with 14% propionic, 27% butyric and 7% isovaleric acids. Operating the acidogenic reactor at this HRT, the effluent was fed to the upflow anaerobic filter. Here HRT was varied between 3-6 days for the best COD removal efficiency and biogas production. At an HRT of 4 days a 90% soluble effluent COD removal efficiency was obtained with an outmost biogas yield of 0.55 m3/kg COD removed.

Two-phase anaerobic treatment of cheese whey

Performance of two-phase anaerobic digestion of cheese whey was investigated in a system consisting of a continuous stirred tank reactor (CSTR) as the acidogenic reactor and an upflow anaerobic filter (UFAF) as the methanogenic reactor. The acidogenic reactor was operated at various hydraulic retention times (HRTs) between 18 hours and 4 days. The results showed that an optimum HRT for the acidogenic reactor with the same organic loading rate (OLR) between 0.5-2 g COD/MLSS day was 24 hours. At this retention time the acidification rate increased up to a maximum of 50%. Volatile fatty acids (VFAs) produced in the acidogenic reactor operating at an HRT of 24 hours were 52% acetic acid, with 14% propionic, 27% butyric and 7% isovaleric acids. Operating the acidogenic reactor at this HRT, the effluent was fed to the upflow anaerobic filter. Here HRT was varied between 3-6 days for the best COD removal efficiency and biogas production. At an HRT of 4 days a 90% soluble effluent COD removal efficiency was obtained with an outmost biogas yield of 0.55 m 3 /kg COD removed.

96/04580 Anaerobic treatment of cheese whey with a downflow-upflow hydrid factor

The production of Macrobrachium rosenbergii monosex populations was examined under intensive growth conditions in cages. It was found that an all-male population yielded 473 g/m2 within 150 days, whereas an all-female population and a mixed population produced 248 g/m2 and 260 g/m2, respectively, during the same growout period. Since the performance of the mixed population in cages is comparable to that of a normal typical juvenile population in commercial earthen ponds, with an average production of 2500–3000 kg/ha, it appears possible to obtain a yield of 4700 kg/ha within 150 days from all-male populations grown under intensive monoculture conditions.A comparison of growth performance of each of the sexes when raised alone and when raised in mixed populations showed that whereas females are strongly affected by the presence of males, resulting in growth inhibition, males are hardly influenced by the presence of females.The findings of this study call for intensive efforts in research directed towards the controlled establishment of prawn monosex populations.

Anaerobic treatment of cheese whey with a downflow-upflow hybrid reactor

ENEA (Italian Agency for New Technology for the Energy and for the Environment) research on the anaerobic treatment of raw cheese whey started in 1990 with the objective of developing a technology suitable for medium-size cheese factories that have growing disposal problems and cannot afford high investment costs for whey valorisation technologies (such as whey protein and lactose recovery, spray drying, etc.). The first attempt was to run a mesophilic hybrid upflow reactor, that was able to reach high removal performances but showed pH unstability which led to failure. In order to obtain better process control, experiments continued on a two-phase CSTR (completely stirred reactor) system that gave good results in terms of stability. To couple process stability and high loads, a new reactor called a downflow-upflow hybrid reactor (DUHR) has been designed. The reactor was able to reach B v (volumetric organic loading rate) values around 10 000 mg COD l −1 day −1, with 98% COD removal and effluent soluble COD (COD sol) values close to 1000 mg.l −1; no external addition of alkalinity was required to maintain a stable pH that was constantly around 6.5–6.7 in the downflow pre-acidification chamber and around 7.5 in the bio-methanation upflow chamber.

Pilot-scale anaerobic treatment of cheese whey by the substrate shuttle process

An experimental system was set up to study the Substrate Shuttle Process (SSP). Whey was fed to an acidogenic UASB reactor. The effluent was intermittently circulated through an Ion Exchange Unit (IEU) containing an anionic exchange resin. During a load cycle, organic acids were adsorbed onto the ion exchange resin. After completion of the load cycle, the ion exchange resin was regenerated by recirculating through it the effluent of a methanogenic UASB reactor, into which the organic acids were released, prior to returning the liquid into the reactor. The pilot system was designed to operate automatically with two IEUs operating in tandem, of which one at a time was operating in a load cycle, while the other was being regenerated. The first experimental period lasted 9 days with a cycle duration of one hour. Acids were removed from the acid UASB liquor, with a concomitant rise of pH and the production of methane in the methanogenic UASB. The acid UASB produced little gas and no methane was detected. The amount of acids circulated through the IEUs was directly proportional with the quantity of methane produced by the methane UASB. After the trial, acid binding capacity had declined to 70% of its original value. A second experiment lasted 118 days, with a cycle duration of five hours. Final conversion of all acid circulated through the IEUs into methane averaged 19%. After initial conditioning of the resin, no significant long-term deterioration of process performance was evident.

Anaerobic treatment of cheese whey in a two‐phase uasb reactor

Abstract The whey produced by the cheese industries can be anaerobically treated. The main operational limitations for single phase reactors are instability and the necessity of adding alkalinity. A double phase reactor has been used and a new operational strategy is proposed. The recirculation of the eflluent of the metanization reactor produces a dilution of the influent that allows a good stability of the system without the necessity of adding alkalinity. COD removal higher than 99% can be obtained operating with Bv = 30 Kg m‐3 d‐1 in the acidification reactor (t=0.45 d) and Bv= 15 Kg m‐3 d‐1 in the metanization reactor (t =0.75 d).

Anaerobic digestion of cheese whey using an upflow anaerobic sludge blanket reactor: III. Sludge and substrate profiles

Anaerobic treatment of cheese whey using a 17·5 litre upflow anaerobic sludge blanket reactor was investigated in the laboratory over a range of influent concentration from 4·5 to 38·1 g COD litre −1 at a constant hydraulic retention time of 5 days. The results indicated that two sludge distribution regions, a sludge bed and a sludge blanket, as well as two distinct reaction phases, acidogenic and methanogenic, were formed. However, as the substrate loading was increased, the acidogenic region extended into the methanogenic region in the upper portion of the reactor until the whole region was acidogenic, leading to the failure of the reactor.

Anaerobic Treatment of Cheese Whey: Start-Up and Operation

Anaerobic Treatment of Cheese Whey: Start-Up and Operation

Anaerobic digestion of cheese whey using up-flow anaerobic sludge blanket reactor

Anaerobic treatment of cheese whey using a 17·5-litre up-flow anaerobic sludge blanket reactor was investigated in the laboratory. The reactor was studied over a range of influent concentration from 4·5 to 38·1 g chemical oxygen demand per litre at a constant hydraulic retention time of 5 days. The reactor start-up and the sludge acclimatization were discussed. The reactor performance in terms of methane production, volatile fatty acids conversion, sludge net growth and chemical oxygen demand reduction were also presented in this paper. Over 97% chemical oxygen demand reduction was achieved in this experiment. At the influent concentration of 38·1 g chemical oxygen demand per litre, an instability of the reactor was observed. The results indicated that the up-flow anaerobic sludge blanket reactor process could treat cheese whey effectively.

Anaerobic expanded bed treatment of whey

Anaerobic treatment of cheese whey offers the dual advantages of energy production and pollution control. Based on the results of a survey among cheese producers in New York State it is shown that up to 46% of the oil and gas needs of a cheese plant could be supplied by methane generated from the by-product whey. This paper also presents the results of a feasibility study with the anaerobic attached film expanded-bed reactor treating whey. It is shown that efficient treatment of whey is possible at low retention times and at high organic loading rates.