Chemical Oxygen Demand Loading Rate Research Articles

High biogas evolution of distillery wastewater under potassium toxicity in a three-stage upflow anaerobic sludge blanket

This investigation aimed to enhance the methanogenic activity of distillery wastewater containing high potassium (K) content in a mesophilic three-stage upflow anaerobic sludge blanket (UASB). The three-stage UASB could not function at a chemical oxygen demand (COD) loading rate greater than 3 kg/m3d due to the K toxicity, causing system failure. The K concentration in the distillery wastewater was 9000–10,000 mg/L, close to the severe inhibitory range for anaerobes (> 12,000 mg/L). Hence, the wastewater was diluted to reach moderate K toxicity. Surprisingly, the three-stage UASB could function effectively, providing high optimum and maximum COD loading rates (20 and 40 kg/m3d, respectively). This was because the three-stage UASB was regulated under a slow stepwise increase in the COD loading rate to achieve fully adapted anaerobe communities for each COD loading rate. This then led to the high ability to withstand the moderate inhibition of K via the successive development of sludge granules.

Process Improvement of a Two-Stage Upflow Anaerobic Sludge Blanket System by Micronutrient Supplement in Relation to Sulfur Transport

The main purpose of this research was to elucidate the influence of the addition of iron alone (0–100 ppm) or with 2 ppm each of cobalt, copper, and nickel on the performance of a two-stage UASB system treating ethanol wastewater. The system consisted of two reactors connected in series. The system was maintained at a fixed chemical oxygen demand loading rate (16 kg/m3d) and 37 °C with a recycle ratio of 1:1. Both Co and Ni were found to be deficient in the ethanol wastewater, while Fe and Cu became inadequate in two-stage UASB. The addition of Fe provided dual benefits of a reduction in both sulfide toxicity and hydrogen sulfide content in produced gas, resulting in marginally improved hydrogen and methane productivities. When the Fe dosage was increased beyond the optimum value of 50 ppm, the process performance drastically declined, as a result of high total volatile fatty acid concentrations that inhibited acidogens and methanogens predominantly present in the 1st and 2nd reactors, respectively. The chemical precipitation of iron sulfide was responsible for the reduction of produced H2S in both aqueous and gaseous phases. The addition of 2 ppm each of Co, Cu, and Ni together with 50 ppm Fe resulted in an enhanced process performance, as indicated by the improved CH4 yield (mL/g COD applied) to about 42.3% compared to that without micronutrient supplement. Supplementation to fulfill the sufficiency of all micronutrients was vital for the maximization of anaerobic digestion (AD) performance, as generally indicated in methanogenic activity.

Treatment of synthetic wastewater and cheese whey by the anaerobic dynamic membrane bioreactor.

The aim of this study was to develop a laboratory-scale anaerobic dynamic membrane bioreactor (AnDMBR) for the treatment of high-strength synthetic and real cheese whey wastewater. We determined the appropriate pore size for a convenient type of support material (nylon mesh) to optimize cake layer formation. The performance of the AnDMBRs was measured in terms of chemical oxygen demand (COD) and solids removal efficiencies. During high-strength synthetic wastewater treatment, the 70-μm pore size AnDMBR achieved COD removal efficiencies of 78% and 96% with COD loading rates of 4.03 and 2.34kgm-3day-1, respectively, while the 10-μm pore size AnDMBR achieved 66% and 92% COD removal efficiencies at COD loading rates of 5.02 and 3.16kgm-3day-1. The 10μm pore size AnDMBR was operated in two periods: first period and second period (before and after physical cleaning) during high-strength synthetic wastewater treatment. The 10-μm pore size AnDMBR removed 83% and 88% of suspended solids during period 1 and period 2, respectively. Furthermore, using a pore size of 10μm retained 72% of solids (973mgL-1) in the reactor outlet. The 10-μm pore size AnDMBR performed better than the 70-μm pore size AnDMBR in terms of cake layer formation. The 10-μm pore size AnDMBR was used to treat real cheese whey wastewater, resulting in COD removal efficiencies ranging from 59% (4.32kgm-3day-1) to 97% (5.22kgm-3day-1). In addition, 85% of suspended solids were removed from real cheese whey wastewater after treatment. The results show that dynamic membrane technology using a pore size of 10μm can be used to treat real industrial wastewater.

A2O-MBR as an efficient and profitable unconventional water treatment and reuse technology: A practical study in a green building residential community

Unconventional water reclamation, recycling, and reuse have been identified as the major approaches for addressing water scarcity in China. The aim of this study was to evaluate the technical and economic feasibility of water reclamation plants (WRP) based on an anaerobic-anoxic-oxic membrane bioreactor (A2O-MBR) system for unconventional water resource (domestic wastewater and rainwater) treatment and reuse in green building residential community. During a year operation and evaluation process, average chemical oxygen demand (COD), biochemical oxygen demand (BOD5), total nitrogen (TN) and total phosphorus (TP) removal efficiencies averaged 83.7 ± 3.2%, 91.6 ± 2.6%, 69.0 ± 6.5% and 74.5 ± 5.5%, respectively. The effluent quality of wastewater treated by the A2O-MBR system complied with the water quality standards for reuse for green building residential community or for direct discharge. Typical seasonal fluctuations of temperature, COD loading rate, BOD5/COD and COD/TN were the key factors affecting pollutants removal efficiencies, and the membrane fouling rate was accelerated at low temperatures. The total cost of capital and operation was 0.406 $/m3, a cost-benefit analysis incorporating both capital and operating expenditures showed that more than 60% of the reclaimed water is reused in the green building, and the full-scale WRP exhibits a positive net present value. These results demonstrated that A2O-MBR is an efficient and profitable technology for nontraditional water resource recycling in green building residential communities in terms of technical and economic feasibility.

Separate production of hydrogen and methane from cassava wastewater with added cassava residue under a thermophilic temperature in relation to digestibility

In this research, the separate production of hydrogen (H2) and methane (CH4) from cassava wastewater with added cassava residue was investigated using a two-stage upflow anaerobic sludge blanket (UASB) system under thermophilic temperature (55 °C) in a continuous mode of operation and steady state condition. The two-stage UASB system was operated under an optimum chemical oxygen demand (COD) loading rate of 10.29 kg/m3d (based on the total volume of both bioreactors) of the cassava wastewater with different concentrations of added cassava residue. The recycle ratio of the effluent from the second bioreactor to the feed flow rate was fixed at 1:1 (v/v). In addition, the solution pH in the first bioreactor was controlled at 5.5, while that in the second bioreactor was not controlled. Under the optimum cassava residue concentration of 1200 mg/L, the produced gas from the first bioreactor contained 42.3% H2, 55% carbon dioxide (CO2) and 2.70% CH4, while that from the second bioreactor contained 70.5% CH4, 28% CO2 and 1.5% H2. Apart from a high H2 and CH4 production performance (45.2 and 150% improvement, respectively, as compared to the system without added cassava residue) under the optimum cassava residue concentration (1200 mg/L) and the controlled COD loading rate (10.29 kg/m3d) of the cassava wastewater, the degradation performance of cellulose and hemicellulose were 41% and 22%, respectively, for the first bioreactor and 23% and 11%, respectively, for the second bioreactor. The digestibility of the cassava residue at thermophilic operation was higher than that at mesophilic temperature.

Comparative study on treatment performance, membrane fouling, and microbial community profile between conventional and hybrid sequencing batch membrane bioreactors for municipal wastewater treatment.

A sequencing batch conventional membrane bioreactor (SB-CMBR) and sequencing batch hybrid membrane bioreactor (SB-HMBR) were operated in parallel under two different hydraulic retention times (HRTs) (namely 12h and 6h), and their chemical oxygen demand (COD) and nutrient removal performance, membrane fouling behavior, and microbial community characteristics were compared. Both systems exhibited high organic matter (> 95%) and ammonium (> 98%) removal performance regardless of the HRT applied. As the HRT was reduced from 12 to 6h, total nitrogen removal slightly increased in both reactors, being higher in the carrier-based MBR, where anoxic zones may have been established within the biofilm. Conversely, total phosphorus removal improved only in the SB-CMBR at the shorter HRT. Moreover, activity batch assays have shown a faster P uptake rate in the SB-CMBR than in the SB-HMBR, a result likely associated with the lower relative abundance of phosphate-accumulating organisms in both adhered and suspended biomass fractions in the hybrid MBR. The results also revealed that more pronounced increases in the transmembrane pressure and, consequently, in the membrane fouling rate at higher COD loading rates were observed in the SB-CMBR, where the soluble microbial products (proteins, polysaccharides, and especially, transparent exopolymer particles), supernatant turbidity, and filamentous bacteria were more significant. Overall, as compared to the conventional MBR, the plastic media-based SB-HMBR showed a lower fouling propensity at all hydraulic conditions tested.

Production of biogas from cassava wastewater using a three-stage upflow anaerobic sludge blanket (UASB) reactor

Abstract In this study, a three-stage upflow anaerobic sludge blanket (UASB) system was developed and tested for hydrogen (H2) and methane (CH4) production from cassava wastewater with an emphasis on CH4 production. The experiment was carried out at mesophilic temperature (37 °C) at different chemical oxygen demand (COD) loading rates from 5 to 18 kg/m3d (based on total liquid holding volume) with a recycle ratio of the final effluent to both the first and second bioreactors at a constant 1: 1 flow rate ratio of feed: final effluent. The first bioreactor was maintained pH at 5.5 while those of the other two bioreactors were not controlled. At an optimum COD loading rate of 15 kg/m3d, the system provided the highest COD removal level (92.5%) and the highest H2 and CH4 yields of 0.43 mL H2/g COD applied, and 328 mL CH4/g COD applied, respectively. The very high productivity of CH4 with the very low H2 productivity resulted from the recycled methanogen sludge from the third bioreactor to the first and second bioreactors. The process performance of the three-stage UASB system in terms of optimum COD loading rate and total energy yield was much higher than those of single and two-stage anaerobic processes.

Three-Stage Anaerobic Sequencing Batch Reactor (ASBR) for Maximum Methane Production: Effects of COD Loading Rate and Reactor Volumetric Ratio

A three-stage anaerobic sequencing batch reactor system was developed as a new anaerobic process with an emphasis on methane production from ethanol wastewater. The three-stage anaerobic sequencing batch reactor system consisted of three bioreactors connected in series. It was operated at 37 °C with a fixed recycle ratio of 1:1 (final effluent flow rate to feed flow rate) and the washout sludge from the third bioreactor present in the final effluent was allowed to be recycled to the first bioreactor. The pH of the first bioreactor was controlled at 5.5, while the pH values of the other two bioreactors were not controlled. Under the optimum chemical oxygen demand loading rate of 18 kg/m3d (based on the feed chemical oxygen demand load and total volume of the three bioreactors) with a bioreactor volumetric ratio of 5:5:20, the system provided the highest gas production performance in terms of yields of both hydrogen and methane and the highest overall chemical oxygen demand removal. Interestingly, the three-stage anaerobic sequencing batch reactor system gave a much higher energy production rate and a higher optimum chemical oxygen demand loading rate than previously reported anaerobic systems since it was able to maintain very high microbial concentrations in all bioreactors with very high values of both alkalinity and solution pH, especially in the third bioreactor, resulting in sufficient levels of micronutrients for anaerobic digestion.

EFFECTS OF COD/TN RATIO AND LOADING RATES ON PERFORMANCE OF MODIFIED SBRs IN SIMULTANEOUS REMOVAL OF ORGANIC MATTER AND NITROGEN FROM RUBBER LATEX PROCESSING WASTEWATER

Two modified sequencing batch reactors (SBRs) specially configured to consist of both oxic and anoxic zones, and be operated with only a single simultaneous oxic/anoxic phase in each treatment batch were tested to evaluate their applicability in treatment of rubber latex processing (RLP) wastewater. The former, R1 was operated with constant aeration, whereas the latter, R2 was operated with air flow varied from lower rate in the early period of the reaction phase to higher rate in the later one. Effects of the chemical oxygen demand (COD) to total nitrogen (TN) ratio and their loading rates on performance of the modified SBRs in simultaneous removal of organic matter and nitrogen from RLP wastewater were investigated. It was observed that performance of the two reactors in removal of COD and ammonium nitrogen was similar, and did not remarkably change when varying COD/TN ratio, as well as COD and TN loading rates in the ranges of 3.4 – 6.0 gCOD/gN, 0.8 – 1.7 kgCOD×m-3×d-1 and 0.15 – 0.34 kgN×m-3×d-1, respectively. The average COD removal efficiencies were over 95%. Ammonium nitrogen was almost completely eliminated in both reactors with effluent concentrations lower than 1.0 mg/L. Nevertheless, TN removal efficiencies of both reactors were significantly increased with increasing the COD/TN ratio from 3.4 to 6.0, and slightly decreased when increasing the TN loading rate from 0.15 to 0.34 kgN×m-3×d-1. The most effective COD/TN ratios were in the range of 5 – 6, at which the maximal TN removal efficiencies of R1 and R2 were 92% and 97%, respectively.

Inhibition of microbial fuel cell operation for municipal wastewater treatment by impact loads of free ammonia in bench- and 45 L-scale

A 45-liter microbial fuel cell (MFC) system was integrated into a full-scale wastewater treatment plant (WWTP). The system was operated under practical conditions with supernatant of a pre-thickener for 50days in order to identify, whether higher power output and energy recovery is possible compared to the use of primary clarifier effluent, as used in a previous study. The higher COD (chemical oxygen demand) loading rates of supernatant neither increased power densities, nor energy recovery, but impact loads of total ammonia nitrogen (TAN) in concentrations >800mg/L (free ammonia nitrogen (FAN)>40mg/L) led to an instant collapse of power output and nutrient removal, which was reversed when ammonia concentrations decreased. Investigations in lab-scale under defined conditions verified that the inhibition of the exoelectrogenic biofilm is in fact caused by high levels of FAN. Here, COD removal, power output and energy recovery constantly decreased, when FAN-concentrations were increased above 64mg/L.

Separate production of hydrogen and methane from biodiesel wastewater with added glycerin by two-stage anaerobic sequencing batch reactors (ASBR)

The objective of this study was to investigate hydrogen and methane production from biodiesel wastewater with added glycerin by using two-stage anaerobic sequencing batch reactors (ASBR) under 37 °C with a recycle ratio of the effluent from the methane ASBR unit-to-the feed flow rate of 1:1. Hydrogen ASBR unit was operated at a constant pH of 5.5 whereas the pH of methane ASBR unit was not controlled. Glycerin was added into biodiesel wastewater having 2330 mg/l COD to obtain a constant feed chemical oxygen demand (COD) of 45,000 m/l. At optimum COD loading rate 11.3 kg/m3d (based on feed COD load and methane ASBR volume), the system provided the highest overall hydrogen and methane production performance (75.15 ml H2/g glycerin removed) which was consistent with the maximum overall COD removal of 76.7% and the highest overall glycerin uptake of 90%. Most of added glycerin was converted to gaseous products with small amounts of organic acids and 1,3 propanediol. The low volumetric ratio of hydrogen ASBR unit-to-methane ASBR unit of 1:6 resulted in low hydrogen yields with high methane yields. Process performance of the two-stage ASBR system was limited by the inhibition of total volatile organic acids produced in both bioreactors.

Biodegradation of Methyl Tertiary Butyl Ether (MTBE) by a Microbial Consortium in a Continuous Up-Flow Packed-Bed Biofilm Reactor: Kinetic Study, Metabolite Identification and Toxicity Bioassays.

This study investigated the aerobic biodegradation of methyl tertiary-butyl ether (MTBE) by a microbial consortium in a continuous up-flow packed-bed biofilm reactor using tezontle stone particles as a supporting material for the biofilm. Although MTBE is toxic for microbial communities, the microbial consortium used here was able to resist MTBE loading rates up to 128.3 mg L-1 h-1, with removal efficiencies of MTBE and chemical oxygen demand (COD) higher than 90%. A linear relationship was observed between the MTBE loading rate and the MTBE removal rate, as well as between the COD loading rate and the COD removal rate, within the interval of MTBE loading rates from 11.98 to 183.71 mg L-1 h-1. The metabolic intermediate tertiary butyl alcohol (TBA) was not detected in the effluent during all reactor runs, and the intermediate 2-hydroxy butyric acid (2-HIBA) was only detected at MTBE loading rates higher than 128.3 mg L-1 h-1. The results of toxicity bioassays with organisms from two different trophic levels revealed that the toxicity of the influent was significantly reduced after treatment in the packed-bed reactor. The packed-bed reactor system used in this study was highly effective for the continuous biodegradation of MTBE and is therefore a promising alternative for detoxifying MTBE-laden wastewater and groundwater.

THE PRODUCTION OF BIOHYDROGEN AND BIOMETHANE FROM CASSAVA WASTEWATER UNDER MESOPHILIC ANAEROBIC FERMENTATION BY USING UPFLOW ANAEROBIC SLUDGE BLANKET REACTORS (UASB)

The main objective was to separately generate biohydrogen (H2) and biomethane (CH4) with the cassava wastewater via the upflow anaerobic sludge blanket reactors (UASB) under the mesophilic temperature (37 ºC). For the first part, the production of H2, the controlled system was managed on the fixed temperature (37 º C) and pH (5.5) included the varied organic concentration in term of chemical oxygen demand (COD) loading rates. As the proper COD loading rate of 25 kg/m3 d, H2 and carbon dioxide (CO2) were mainly generated gases which provided the highest specific H2 production rate of 0.39 l H2/l d and the highest H2 yield of 39.83 l H2/kg COD removed. For the second part, the effluent liquid that generated from the stage of H2 production on COD loading rate of 25 kg/m3 d was fed to the UASB with the fixed temperature (37 °C) and no pH control. The highest specific CH4 production rate of 0.91 l CH4/l d and the highest CH4 yield of 115.23 l CH4/kg COD removed were shown on the proper COD loading rate of 8 kg/m3 d.

An integrated mathematical model for chemical oxygen demand (COD) removal in moving bed biofilm reactors (MBBR) including predation and hydrolysis

An integrated mathematical model is proposed for modelling a moving bed biofilm reactor (MBBR) for removal of chemical oxygen demand (COD) under aerobic conditions. The composite model combines the following: (i) a one-dimensional biofilm model, (ii) a bulk liquid model, and (iii) biological processes in the bulk liquid and biofilm considering the interactions among autotrophic, heterotrophic and predator microorganisms. Depending on the values for the soluble biodegradable COD loading rate (SCLR), the model takes into account a) the hydrolysis of slowly biodegradable compounds in the bulk liquid, and b) the growth of predator microorganisms in the bulk liquid and in the biofilm. The integration of the model and the SCLR allows a general description of the behaviour of COD removal by the MBBR under various conditions. The model is applied for two in-series MBBR wastewater plant from an integrated cellulose and viscose production and accurately describes the experimental concentrations of COD, total suspended solids (TSS), nitrogen and phosphorous obtained during 14 months working at different SCLRs and nutrient dosages. The representation of the microorganism group distribution in the biofilm and in the bulk liquid allow for verification of the presence of predator microorganisms in the second reactor under some operational conditions.

Performance of anaerobic fluidized membrane bioreactors using effluents of microbial fuel cells treating domestic wastewater

Anaerobic fluidized membrane bioreactors (AFMBRs) have been mainly developed as a post-treatment process to produce high quality effluent with very low energy consumption. The performance of an AFMBR was examined using the effluent from a microbial fuel cell (MFC) treating domestic wastewater, as a function of AFMBR hydraulic retention times (HRTs) and organic matter loading rates. The MFC–AFMBR achieved 89±3% removal of the chemical oxygen demand (COD), with an effluent of 36±6mg-COD/L over 112days operation. The AFMBR had very stable operation, with no significant changes in COD removal efficiencies, for HRTs ranging from 1.2 to 3.8h, although the effluent COD concentration increased with organic loading. Transmembrane pressure (TMP) was low, and could be maintained below 0.12bar through solids removal. This study proved that the AFMBR could be operated with a short HRT but a low COD loading rate was required to achieve low effluent COD.

Evaluation of granular sludge for secondary treatment of saline municipal sewage

This study examined the impact of chemical oxygen demand (COD) loading and dissolved oxygen (DO) concentration on the stability and performance of granular sludge treating high saline municipal sewage. Under high DO concentrations of 4.0–7.0 mg/L, and COD loading rates of 0.98 and 1.55 kg/m3/d, rapid settling granules were established within four weeks of start-up. Under the highest COD load, a reduction in DO lead to the rapid deterioration of the sludge volume index (SVI) and washout of granules due to prolific growth of the filament Thiothrix Type 021N. Conversely, when operated under a lower COD load, a reduction in DO concentration had no adverse impact on the stability of SVI and granules. A decrease in DO also improved nitrogen removal performance, where simultaneous removal of ammonium (98%), total nitrogen (86%) and BOD5 (98%) were achieved when median DO concentrations were between 1.0 and 1.5 mg/L. Phosphate removal was lower than expected, however the level of biological phosphate removal activity observed appeared sufficient to maintain granule stability, even under low DO concentrations. Nitrous oxide emissions were also characterised, which ranged between 2.3 and 6.8% of the total nitrogen load. Our results confirmed that granular sludge is a viable option for the treatment of saline sewage.

Effects of aeration on/off times and hydraulic retention times in an intermittently aerated membrane bioreactor

Intermittently aerated membrane bioreactor is a process that combines an intermittently aerated bioreactor with a membrane. A membrane bioreactor can achieve complete separation between solids and liquids, and improve nitrogen removal because the reactor contains bacteria relevant to nitrifying and denitrifying. This paper is an investigation into removal efficiencies on two operation factors (aeration on/off times and hydraulic retention times (HRTs)). Permeate concentrations of T-N and T-P in 60 min-on/60 min-off were 19.6 and 4.41 mg/L, respectively, and permeate concentrations of T-N and T-P in 30 min-on/30 min-off were 22.7 and 4.56 mg/L, respectively. Accordingly, we found that 60 min-on/60 min-off was superior to 30 min-on/30 min-off. This was due to the high mixed liquid suspended solid concentration and the sufficient aerobic/anoxic time for the reaction. In the experiments with HRTs of 6, 9, and 12 h, the removal efficiency of organic matter was above 90% under all conditions. However, the HRT of 6 h was the best condition for removal efficiencies of T-N and T-P, due to high chemical oxygen demand loading rates per unit time of the influent.

생물학적 막분리 공정에서 수동흡착 상태에서의 유기물 유입 부하에 따른 소수성 막의 오염도 분석

This paper investigated the membrane fouling potential at the state of passive adsorption which is no permeation with the test modules on COD (Chemical oxygen demand) loading rates, examined the recovery rate and resistance on membrane fouling by three cleaning manners of hydrophobic membrane in a bioreactor. The results showed that high COD loading led to the increase of extra-cellular polymeric substances and filtration resistance. The permeability resistance from 1st day to 63rd day was getting increased, however, the value of permeability resistance after 63th day during the operation period was almost same level at three COD loading rates, it was due that the biomass adhesion on membrane surface at the state of passive adsorption reached to the critical state. Also, the final recovery rates after three cleaning manners were 78%, 72% and 69% at the COD loading concentrations of 250 mg/L, 500 mg/L and 750 mg/L respectively, and then recovery rate by physical cleaning at Run 2 and Run 3 was decreased after 40th day, it proved that biomass cake, which is not easily removed, was formed on the membrane surface because of high COD loading rate and EPS concentration.

Development of enhanced SNAD process in a down-flow packed bed reactor for removal of higher concentrations of NH4–N and COD

Enhanced simultaneous partial nitrification, anammox and denitrification (SNAD) process was developed using a 2.4L down-flow packed bed reactor for removing higher concentrations of ammonia and chemical oxygen demand (COD) (at COD/NH4–N ratio=1.0) in low dissolved oxygen concentrations (≤0.35mg/L). SNAD was developed using flocculent type activated sludge sourced from a tannery common effluent treatment plant and the reactor was operated continuously for 122d at various loading rates with hydraulic retention time (HRT) varied between 12h and 3h. The reactor was operated in room temperature and the liquid temperature varied between 28 and 32°C. The performance of the reactor at 3h HRT showed enhanced removal rates of NH4–N (2.8g/Ld), total nitrogen (2.5g/Ld) and COD (4.9g/Ld) at ammonia and COD loading rates of 5.4g/Ld. The nitrogen removal was due to the competitive involvement of anammox (∼50%) and denitrification (∼50%) and these processes were confirmed by conducting separate batch experiments. There was no external addition of alkalinity at higher loading rates corresponding to the requirement of oxidation of NH4–N. This study demonstrates SNAD for enhanced rate of removals of NH4–N and COD at high concentrations compared to the reported results in literature and indicates a potential application.

Performance assessment of two-stage anaerobic digestion of kitchen wastes

This study is aimed at investigating the performance of the two-phase anaerobic digestion of kitchen wastes in a lab-scale setup. The semi-continuous experiment showed that the two-phase anaerobic digestion of kitchen wastes had a bioconversion rate of 83%, biogas yield of 338 mL·(g chemical oxygen demand (COD))−1 and total solid conversion of 63% when the entire two-phase anaerobic digestion process was subjected to an organic loading rate (OLR) of 10.7 g·(L d)−1. In the hydrolysis–acidogenesis process, the efficiency of solubilization decreased from 72.6% to 41.1%, and the acidogenesis efficiency decreased from 31.8% to 17.8% with an increase in the COD loading rate. On the other hand, the performance of the subsequent methanogenic process was not susceptible to the increase in the feeding COD loading rate in the hydrolysis–acidogenesis stage. Lactic acid was one of the main fermentation products, accounting for over 40% of the total soluble COD in the fermentation liquid. The batch experiments indicated that the lactic acid was the earliest predominant fermentation product, and distributions of fermentation products were pH dependent. Results showed that increasing the feeding OLR of kitchen wastes made the two-stage anaerobic digestion process more effective. Moreover, there was a potential improvement in the performance of anaerobic digestion of kitchen wastes with a corresponding improvement in the hydrolysis process.