Endogenous Decay Coefficient Research Articles

Testing an aerobic fluidized biofilm process to treat intermittent flows of oil polluted wastewater

An aerobic fluidized biofilm process of treating oil-polluted wastewater has been studied. A series of batch experiments were conducted using synthetic wastewater and the kinetic coefficients were evaluated. The maximum rate of substrate utilization per unit mass microorganisms (K) was 1.6 days-1, the substrate concentration at one-half the maximum growth rate (Ks) was 26 mg/L, the maximum specific growth rate (m) was 1.0 days-1, the ratio of the mass cells formed to the mass of substrate consumed (Y) was 0.61, and the endogenous decay coefficient (Kd ) was 0.044 days-1. The kinetic coefficients obtained were within the range of municipal wastewater. It was observed that up to 1500 mg/L oil (Motor oil SAE–40) could be degraded in a fluidized bed bioreactor (FBBR). The experiments, however, were limited to the oil concentration within a range of 1000-2600 mg/L. Average biofilm thickness () under specific conditions was found to be 22 m and average oil degradation rate of 0.053 mg oil/mg biomass/hour was measured in the FBBR. The results also support that the increase in the concentration of oil in the treatment process reduced significantly the degradation rate of non-oil carbon.

Kinetics of Cometabolic Transformation of 4-chlorophenol and Phenol Degradation by Pseudomonas putida Cells in Batch and Biofilm Reactors

The biodegradation kinetics of 4-chlorophenol (4-CP) and phenol and microbial growth of Pseudomonas putida (P. putida) cells were estimated in batch and biofilm reactors. The kinetic parameters of cells on phenol were determined using the Haldane formula. The maximum specific growth rate of P. putida on phenol, the half-saturation constant of phenol and the self-inhibition constant of phenol were 0.512 h−1, 78.38 mg/L and 228.5 mg/L, respectively. The yield growth of cells on phenol (YP) was 0.618 mg phenol/mg cell. The batch experimental results for the specific transformation rate of 4-CP by resting P. putida cells were fitted with Haldane kinetics to evaluate the maximum specific utilization rate of 4-CP, half-saturation constant of 4-CP, and self-inhibition constant of 4-CP, which were 0.246 h−1, 1.048 mg/L and 53.40 mg/L, respectively. The negative specific growth rates of cells on 4-CP obtained were fitted using a kinetic equation to investigate the true transformation capacity and first-order endogenous decay coefficient, which were 4.34 mg 4-CP/mg cell and 5.99 × 10−3 h−1, respectively. The competitive inhibition coefficients of phenol to 4-CP transformation and 4-CP to phenol degradation were 6.75 and 9.27 mg/L, respectively; therefore, phenol had a higher competitive inhibition of 4-CP transformation than the converse. The predicted model examining cometabolic transformation of 4-CP and phenol degradation showed good agreement with the experimental observations. The removal efficiencies for phenol and 4-CP were 94.56–98.45% and 96.09–98.85%, respectively, for steady-state performance.

Kinetics of Anaerobic Digestion of Unripe Plantain Peels

This study was carried out to investigate the biogas production obtained from anaerobic digestion of unripe plantain peels (PP) and the kinetics of the digestion process. 400 g of dried and shredded unripe plantain peels were mixed with 200 ml of water and put into 1 L digester and observed for biogas for hydraulic retention time (HRT) of 15 days by the method of downwards displacement. The cumulative biogas volume obtained after digestion was 285 ml. The COD removal efficiency of 72.5% was achieved. The kinetics of PP digestion was evaluated using first order, Monod, Contois and, Grau second-order models. Results showed that the kinetics of anaerobic digestion of PP followed the first-order model with a constant (K) of 0.095 day-1. Monod kinetics was evaluated and the maximum rate of substrate utilization (K), the half velocity constant (KS), endogenous decay coefficient (Kd), biomass growth yield (Y) and, maximum specific microorganism growth rate (µmax) obtained were 0.7615 day-1, 16.20 mg/l, 0.0047 day-1, 0.0112 mgVSS mgCOD-1 and, 0.009 day-1 respectively. These results revealed that inoculation would be required to increase the rate and volume of biogas production. Both first-order and Monod models gave a high coefficient of determination indicating that first order and Monod models can be used to model the digestion of PP. Contois model gave values of µmax and β as 0.011 day-1 and 0.644 mgCOD mgVSS-1 respectively. The result obtained has shown that the digestion of PP did not follow second-order kinetics.

Foaming control and determination of biokinetic coefficients in membrane bioreactor system under various organic loading rate and sludge retention time

This work aims to control foaming in a submerged membrane bioreactor (SMBR) by optimizing the organic loading rate (OLR) and sludge retention time (SRT) values to decrease the extracellular polymeric substance (EPS) production used for the pharmaceutical wastewater treatment. Four lab-scale SMBRs were operated for a period of more than 8 months to determine the biokinetic coefficients and optimize the SMBR systems operation under the SRT of 5, 10, 15, 20, 25 days and OLRs of 0.03-0.32 gCOD/L.day. The investigation revealed that the lowest foaming quantity was at an organic loading rate of 0.32 gCOD/L.day and a sludge retention time of 15 days related to few protein concentration of EPS. The results also showed that the foaming quality at the OLR of 0.03 gCOD/L.day was higher compared to the greater OLRs in all SRTs. It was found that the yield (Y), the endogenous decay coefficient (kd), the maximum specific growth rate (μmax), and the saturation constant (Ks) of four SMBRs were in the range of 0.073-0.310 mg/mg, 0.985-3.119 day−1, 1.249-3.672 day−1, and 2.63-106.671–232.55 mg/mg, 1–3.156 day mgCOD/L, respectively. Furthermore, the most appropriate operating condition to activated sludge among the SMBRs was the OLR of 0.1 gCOD/L.day and SRT of 15 days. Under these optimum conditions, a 92.8 % COD removal efficiency and 3.708 1/day μmax were achieved.

Aerobic cometabolism of 1,4-dioxane by isobutane-utilizing microorganisms including Rhodococcus rhodochrous strain 21198 in aquifer microcosms: Experimental and modeling study

Aerobic cometabolism of the emerging contaminant 1,4-dioxane (1,4-D) by isobutane-utilizing microorganisms was assessed in pure culture and aquifer microcosm studies. The bacterium Rhodococcus rhodochrous strain ATCC 21198 transformed low, environmentally-relevant concentrations of 1,4-D when grown on isobutane. Microcosms were constructed with aquifer solids from Fort Carson, Colorado, a site contaminated with 1,4-D and trichloroethene (TCE). Multiple additions of isobutane and 1,4-D over 300 days were transformed in microcosms biostimulated with isobutane and microcosms bioaugmented with strain 21198. Results showed that, over time and with sufficient inorganic nutrients, biostimulation of native microorganisms with isobutane was just as effective as bioaugmentation with strain 21198 to achieve 1,4-D transformation in the microcosms. The presence of TCE at 0.2 mg/L did not inhibit 1,4-D transformation, though TCE itself was not readily transformed. An iterative process was used to determine kinetic parameter values to fit Michaelis-Menten/Monod models to experimental data for simultaneous isobutane utilization, biomass growth, and cometabolic transformation of 1,4-D. Parameter optimization resulted in good model fit to the data over multiple transformations of isobutane and 1,4-D in both short- and long-term experiments. Results suggest low concentrations of 1,4-D studied in the microcosms were cometabolically transformed according to a pseudo first-order rate of 0.37 L/mg TSS/day of 21198. Isobutane consumption was modeled with a maximum rate of 2.58 mg/mg TSS/day and a half saturation constant of 0.09 mg/L. 1,4-D transformation was competitively inhibited by the presence of isobutane and transformation rates were significantly reduced when inorganic nutrients were limiting. Simulations of the repeated additions found a first-order microbial endogenous decay coefficient of 0.03 day−1 fit the alternating periods of active transformation and stagnation between isobutane and 1,4-D additions over approximately one year. The model fitting process highlighted the importance of determining kinetic parameters from data representing low concentrations typically found in the environment.

KINETIC STUDY OF PALM OIL MILL EFFLUENT (POME) TREATMENT BY ACTIVATED SLUDGE

Kinetic parameter is a basis for design and optimization of activated sludge POME treatment. In fact, most of the kinetic parameter value used in design and optimization are default values taken from municipal wastewater. The kinetic parameters for POME treatment have not been thoroughlystudied and most of the system is using the Activated Sludge Models (ASM), either in modelling or design. Thus, the kinetic study of POME treatment by activated sludge system were carried out to obtain the kinetic parameters for the POME treatment plant design calculation.In this study, POME treatment was carriedout in batch studiesinto 14 L aeration tank with activated sludge for the biological oxidation process with optimum pH at 6.5 ± 0.1, MLVSS of 2000 ± 200 mg/Lfor HRT of 48 h and feeding with 650 ± 20 mg BOD3/L of anaerobic treated POME, while SRT was controlled at a range of 10 days to 20 days with interval of 2 days for the kinetic study experiment. From this kinetic study, the kinetic parameters for COD and BOD basis had been determined for maximum yields coefficient (Y), endogenous decay coefficient (kd), maximum specific substrate utilization rate (k) and half-velocity constant (Ks) at 0.2369 mg VSS/mg COD, 0.1060 day-1, 2.2717 day 1 and 758.7705 mg/L for COD basis whilst the kinetic parameters value for BOD basis were 0.6718 mg VSS/mg BOD3, 0.0658 day-1, 1.4136 day-1 and 556.1526 mg/L, respectively. Since the BOD is one of the discharge parameters in discharge regulatory, thus kinetic parameters for BOD basis will be used for the system design of POME treatment.

Simulation of in situ biodegradation of 1,4-dioxane under metabolic and cometabolic conditions

Bioaugmentation is an option for aerobic remediation of groundwater contaminated with 1,4-dioxane. One approach uses microbes that cometabolize 1,4-dioxane following growth on a primary substrate (e.g., propane), whereas another uses microbes (e.g., Pseudonocardia dioxivorans CB1190) capable of using 1,4-dioxane as a sole substrate. The relative merits of these approaches are difficult to distinguish based on field data alone, and theoretical analyses of these processes have yet to be published. The objective of this study was to compare these remediation options using a transport model that incorporates advection, dispersion and biodegradation reactions described by multi-substrate Monod kinetics and co-inhibition effects. The transport model was coupled to an approximate steady-state air sparging simulation used to estimate gas (propane and oxygen) distribution at the field scale. The model was calibrated with field data for 1,4-dioxane and propane concentrations from a previously reported pilot study. The two remediation approaches were evaluated under different conditions that vary the initial concentration of 1,4-dioxane and the loading rates of oxygen, propane, and biomass. The metrics used to evaluate the remediation success were the time to reach an average 1,4-dioxane concentration of 1 μg L−1 and the percent of 1,4-dioxane biodegraded after 10 years of simulation. Results indicate that the initial concentration of 1,4-dioxane strongly influences which remediation approach is more effective. When initial concentrations were <10 mg L−1, propane-driven cometabolism led to faster remediation; whereas metabolic biodegradation was faster when initial concentrations were 10 mg L−1 or higher. Below 0.25 mg L−1, the viability of metabolic biodegradation improved, although cometabolism by propanotrophs still required less time to reach 1 μg L−1. Biomass injection rates had a strong effect on the rate of metabolism but not cometabolism because continuous input of primary substrate supported growth of propanotrophs. The performance of both cultures was negatively affected by a decrease in oxygen injection rate. The endogenous decay coefficient and the dispersion rate for biomass had a significant impact on cometabolic and metabolic biodegradation of 1,4-dioxane. The maximum specific rate for cometabolism of 1,4-dioxane, the dispersion rate for 1,4-dioxane, and effective porosity also had significant effects on the time to achieve remediation with propanotrophs.

Biokinetic coefficients determination of a MBR for styrene and ethylbenzene as substrate base on Andrews model

In this study, a lab-scale membrane bioreactor (MBR) was operated for a period of more than 10 months to determine the biokinetic coefficients of the system under the hydraulic retention times (HRT) of 20, 15 and 10 hrs and sludge retention times (SRT) of 5-20 days. The results revealed that the biological removal efficiency of styrene and ethylbenzene at a solid retention time of 20 day and a hydraulic retention time of 15 hr was higher compared to a SRT of 10 day and at the same HRT. The results also showed that the yield (Y), the endogenous decay coefficient (kd), the maximum specific growth rate (μmax), and the saturation constant (Ks) for styrene and ethylbenzene as substrate were 0.60 and 0.60 mg/mg, 0.25 and 0.25 day−1, 0.188 and 0.363 h-1, and 0.146 and 2.82 mg /l, respectively. Furthermore, ethylbenzene was more appropriate as a source of carbon to activated sludge in the membrane bioreactor than the styrene which had a lower μmax than ethylbenzene.

Modeling Kinetics of Anaerobic Co-Digestion of Poultry Litter and Wheat Straw Mixed with Municipal Wastewater in a Continuously Mixed Digester with Biological Solid Recycle Using Batch Experimental Data

The half-saturation rate coefficient and maximum rate constant in the Monod model, yield coefficient defined as the ratio of microbial mass to substrate mass, and endogenous decay coefficient are important kinetic parameters for design of anaerobic digestion. These parameters are usually determined from a continuous stable operation of anaerobic digestion, which is more difficult and complex than batch operation in laboratory scale. In this study, a novel method has been developed to determine those parameters from data of batch experiments. To verify this method, kinetics of batch anaerobic co-digestion of poultry litter and wheat straw mixed with municipal wastewater at three total solid (TS) levels (2, 4, and 8% TS) and 50% volatile solid (VS) of wheat straw (VSWS) were investigated. The results showed that the maximum specific methane volume (209 mL (initial g VS)−1)) was reached at 4% TS of 50% VSWS. Using the developed method, the kinetic parameters of endogenous decay coefficient, yield coefficient, maximum rate constant, and half-saturation coefficient were determined to be between 0.57 × 10−3 and 1.2 × 10−3 d−1, 0.00938 and 0.0644 g volatile suspended solid (VSS) (VS)−1, 1.394 and 13,797 d−1, and 1.6 × 10−8 and 99,996 g. The kinetic parameters obtained were used to simulate kinetic behaviors of a continuous mixed digester with biological solid recycle. The simulated results showed that the dilution rate was very significant for methane volume produced, VS and VSS concentrations in digestion operation. The maximum methane volume could be predicted to be 3071 and 4152 mL for 2 and 4% TS, respectively.

A novel salt-tolerant bacterial consortium for biodegradation of saline and recalcitrant petrochemical wastewater

Treatment of a saline petrochemical wastewater with BOD5/COD ratio of less than 0.1 was investigated using a consortium consisted of three isolated salt-tolerant bacteria namely, Kocuria turfanesis, Halomonas alkaliphila and Pseudomonas balearica. Selected bacteria were isolated from petrochemical wastewater containing mineral salt mediums of 3% salinity. A lab-scale activated sludge bioreactor was used for startup in batch mode operation and after obtaining the MLSS concentration of about 3000 mg/L, the operation was changed to continuous flow mode to determine the biokinetic coefficients under different organic loading rates of 0.33–1.21 kg CODm−3 d−1. The COD removal efficiency of 78.7%–61.5% was observed for treatment of real saline wastewater with a decreasing trend along with increasing the organic loading rate. In addition, results of kinetic investigation demonstrated that the yield(Y), endogenous decay coefficient (kd), maximum reaction rate (Kmax), maximum specific growth rate (μmax) and saturation constant (Ks) were 0.54 mg VSS mg COD−1, 0.014 day−1, 1.23 day−1, 0.66 day−1, and 1315 mg L−1, respectively.

Assessment of Kinetic Coefficients for Chrome Tannery Wastewater Treatment by Activated Sludge System

Activated sludge process is feasible and extensively method used for biological treatment of sewage and industrial wastewaters. The system is usually designed based on the simplified hydraulic related parameters. But design of biological treatment system based on hydraulic considerations is not reasonable to ensure efficient treatment due to the extensive variation in the composition of wastewater and also for complex nature of biochemical reactions occurring in the treatment processes. Hence kinetic approach can be an option for appropriate design of biological treatment systems rather than hydraulic parameters considerations. The present study is aimed to develop kinetic coefficients for the treatment of chrome-tannery wastewater using activated sludge process. A laboratory-scale treatment unit subsuming an aeration tank and a clarifier were used for this system. The treatment unit was operated continuously for 80 days by varying the hydraulic retention time from 3 to 12 days. BOD for both influent and effluent as well as mixed liquor volatile suspended solid (MLVSS) of aeration tank were determined at different retention time to yield data for kinetic coefficients. The substrate utilization rate coefficient (k) was 0.624 day−1 while the half velocity constant (KS) was 38.42 mg/L, yield coefficient (Y) was found to be 0.674 mgMLVSS/mgBOD and the endogenous decay coefficient (Kd) was found as 0.068 day-1. These coefficients can be utilized for the rational design of activated sludge system for the treatment of chrome tannery wastewater.

Determination of Kinetic Parameters in Integrated Fixed Film Activated Sludge for Amol's Industrial Park Wastewater Treatment Plant

In this study the performance of integrated fixed film activated sludge system (IFAS) in Amol industrial wastewater treatment plant (Amol, Iran) in treatment of food industrial wastewater was investigated. In addition, kinetic coefficients were evaluated for the system. The capacity of this system was 1700 cubic meters per day; that includes different process comprising physical and biological treatment, disinfection, sludge thickening, digestion and dewatering. COD removal efficiency and kinetic coefficients including yield coefficient (Y), half saturation coefficient (Ks), maximum substrate utilization rate constant (k) and endogenous decay coefficient (kd) were evaluated. The obtained results demonstrated that except Ks other coefficient were in the normal range that was frequently reported for conventional activated sludge in the literature. The COD removal efficiency was about 98 to 99 percent. The results indicated that there is a direct relationship between the variation of kd and Ks with effluent substrate concentration; while, the relationship between rate constant (k) and effluent COD is reversed. Finally, the effect of increasing sludge retention time (SRT) on COD removal was also studied. It was concluded that COD removal increased with an increase active solid retention time to a certain point, behind that point there was no significant changes observed.

A simplified stoichiometric kinetic model for estimating the concentration of reaction products in anaerobic digestion

ABSTRACTModelling the anaerobic digestion process is often complex and needs to consider many input parameters. This study simplified the modelling procedure by developing an idealized stoichiometric kinetic model that simulates the anaerobic digestion process with only a few parameters: composition coefficients (α and β), maximum substrate utilization rate (qmax), endogenous-decay coefficient (b), biodegradable fraction (fd), and temperature coefficient (Ф). We validated the model with the operating results of a pilot two-phase anaerobic digester for food wastewater disposal and calculated using the MATLAB programing software. The comparison between the experimental and model simulation results demonstrated a good agreement. The developed model correctly simulated the fate of chemicals in the anaerobic digestion process.

Biokinetic coefficients of anaerobic immersed membrane bioreactor (AnIMBR) treating dairy wastewater

In order to determine biokinetic coefficients, namely, cell yield (Y), maximum specific growth (μm), endogenous decay coefficient (kd), and saturation constant (Ks), a lab-scale anaerobic immersed membrane bioreactor (AnIMBR) was used. The AnIMBR was performed at different values of mixed liquor suspended solids (mixed liquor suspended solids (MLSS) values of 5,000, 10,000, and 15,000 mg/L) and influent chemical oxygen demand (chemical oxygen demand (COD) values of 2,000, 4,000, 6,000, and 8,000 mg/L). The results showed that Y, μm, kd, and Ks were in the ranges of 0.2022–0.427 mg/mg, 0.0334–0.1095 (1/d), 0.0009–0.0022 (1/d), and 4612–6663 (mg COD/L), respectively. Values of Y, μm, and kd were in the range of those reported in the published literature for various anaerobic processes using different substrates. However, values of Ks, obtained from the current investigation, were higher than those reported in the published literature. This can be attributed to the fact that by increasing the influent COD and decreasing the MLSS concentrations, the process removal efficiency will decrease and in turn, Ks will increase. Effluent COD at different values of MLSS was simulated and sensitivity analysis showed that the process performance was more sensitive to Ks than other biokinetic coefficients.

Kinetics of batch anaerobic co-digestion of poultry litter and wheat straw including a novel strategy of estimation of endogenous decay and yield coefficients using numerical integration

The kinetics of anaerobic co-digestion of poultry litter and wheat straw has not been widely reported in the literature. Since endogenous decay and yield coefficients are two basic parameters for the design of anaerobic digesters, they are currently estimated only by continues experiments. In this study, numerical integration was employed to develop a novel strategy to estimate endogenous decay and yield coefficients using initial and final liquid data combined with methane volumes produced over time in batch experiments. To verify this method, the kinetics of batch anaerobic co-digestion of poultry litter and wheat straw at different TS and VS levels was investigated, with the corresponding endogenous decay and (non-observed) yield coefficients in the exponential periods determined to be between 0.74×10(-3) and 6.1×10(-3)d(-1), and between 0.0259 and 0.108g VSS (gVS)(-1), respectively. A general Gompertz model developed early for bio-product could be used to simulate the methane volume profile in the co-digestion. The same model parameters obtained from the methane model combined with the corresponding yield coefficients could also be used to describe the VSS generation and VS destruction.

Anammox endogenous metabolism during long-term starvation: Impacts of intermittent and persistent modes and phosphates

Starvation of anaerobic ammonium oxidation (anammox) bacteria can occur in underloaded bioreactors or during the storage of sludge. In this study, the impacts of intermittent and persistent resting modes and phosphates on the endogenous metabolism of anammox bacteria during long-term starvation were investigated. Batch experiments were performed to evaluate the response of anammox granules to different modes of starvation (persistent-resting and intermittent-resting cells) in the presence and absence of phosphates. The endogenous decay coefficient of anammox granules (based on the decreased biomass) over a 30-d persistent starvation period was 0.0062d−1, while the intermittent starvation by means of providing substrates every 10days accelerated the biomass decay approximately twice (0.0110d−1). Moreover, the intermittent-resting cells displayed exacerbated decreases in specific anammox activity relative to the persistent-resting cells, whereas no significant difference was observed in the heme c contents. Regardless of the physiological status of the cells, the presence of low levels of phosphates may be beneficial; however, a high level of phosphates is not recommended. Although different metabolic strategies were adopted depending on the starvation mode, anammox bacteria possessed a better survival strategy via a relatively low maintenance energy requirement to ensure their survival in nutrient-limited systems. In addition, the variations in extracellular protein-like components were indicative of different intracellular metabolic regulation mechanisms. These results provide a better understanding of the endogenous metabolism of anammox bacteria.

Modeling effects of DO and SRT on activated sludge decay and production

The effect of dissolved oxygen (DO) on the endogenous decay of active heterotrophic biomass and the hydrolysis of cell debris were studied. With the inclusion of a hydrolysis process for the cell debris, mathematical models that are capable of quantifying the effects of DO and sludge retention time (SRT) on concentrations of active biomass and cell debris in activated sludge are presented. By modeling the biomass cultivated with unlimited DO, the values of endogenous decay coefficient for heterotrophic biomass, the hydrolysis constant of cell debris, and the fraction of decayed biomass that became cell debris were determined to be 0.38 d−1, 0.013 d−1, and 0.28, respectively. Results from modeling the biomass cultivated under different DO conditions suggested that the experimental low DO (∼0.2 mg/L) did not inhibit the endogenous decay of heterotrophic biomass, but significantly inhibited the hydrolysis of cell debris with a half-velocity constant value of 2.1 mg/L. Therefore, the increase in sludge production with low DO was mainly contributed by cell debris rather than the active heterotrophic biomass. Maximizing sludge production during aerobic wastewater treatment could reduce aeration energy consumption and improve biogas energy recovery potential.

Anaerobic Digestion Treatment of Soft Drink Wastewater

The aim of this study was to treat soft drink industrial wastewater by anaerobic digestion. Digestion lasted for a hydraulic retention time of 30 days. The total quantity of biogas produced was 80ml. The wastewater was characterized after digestion. The result showed that chloride, total dissolved solid, total suspended solid and chemical oxygen demand met the specifications of the world health organization for the safe disposal of wastewater into the water body. The kinetics of anaerobic digestion of the wastewater was described by first order kinetic model. The net specific growth rate of the wastewater was evaluated and observed to reduce with time. The kinetic parameters such as maximum rate of substrate utilization, half velocity or saturation constant, endogenous decay coefficient, biomass or microbial growth yield and maximum specific microorganism growth rate obtained were 0.350day−1, 204.12mg/l, 0.0222day−1, 0.194day−1 and 0.0679day−1 respectively. This revealed that inoculation would be needed for increased volume of biogas production and for an increased digestion rate to be obtained. Based on the endogenous decay coefficient and biomass yield values, a small sludge handling facility would be required in the absence of inoculation during digestion.

Kinetics of Batch Anaerobic Digestion of Vegetable Oil Wastewater

The treatment of vegetable oil industrial wastewater by anaerobic digestion was studied. A hydraulic retention time (HRT) of 35 days was used for the digestion process. The maximum volume of biogas production by downward displacement of water was 150ml. After digestion, the following parameters (chloride, total dissolved solids, total suspended solids, total solids total nitrogen, chemical oxygen demand, biological oxygen demand) fell within the limits prescribed by WHO (World Health Organization). The kinetic parameters such as maximum rate of substrate utilization (K), half velocity or saturation constant (Ks), endogenous decay coefficient (Kd), biomass or microbial growth yield (Y) and maximum specific microorganism growth rate (μmax) were determined as 0.8215 day 1, 163.31mg/l, 0.0838 day 1, 0.2813mg/mg and 0.231 day 1 respectively. The kinetics of anaerobic digestion of the wastewater was described by first order kinetic model. The net specific growth rates (μnet) for the wastewater also was observed to reduce with time. These values indicated that inoculation of the feed with microorganism would be required to increase the rate of digestion and therefore will require a large digester.

Anaerobic Digestion of Slaughterhouse Wastewater: A Kinetics Study

Anaerobic digestion was used to study the treatment of slaughterhouse industrial wastewater (SHW). Digestion period of 50 days was observed. This hydraulic retention time (HRT) was used because that was when negligible biogas production was obtained with. The gas was collected in a measuring cylinder by the use of downward displacement of water. The maximum volume of biogas produced was 537ml. Some of the characteristics of the wastewater such as chloride, total nitrogen, calcium were within the limit prescribed by WHO (world health organization). The kinetic parameters such as maximum rate of substrate utilization (K), half velocity or saturation constant (KS), endogenous decay coefficient (Kd), biomass or microbial growth yield (Y) and maximum specific microorganism growth rate (μmax) were evaluated as 31.847day 1, 25,347.77mg/l, 0.009day 1, 0.034 mg/mg and 1.073day 1 respectively. The kinetics data of anaerobic digestion of the wastewater fitted first order kinetic model. The net specific growth rates (μnet) reduced with time. The values of the kinetics parameters showed that digestion of SHW did not require inoculation of the feed with microorganism to increase the rate of digestion.