Feed COD Concentration Research Articles

Saline Wastewater Treatment By Halophile-Supplemented Activated Sludge Culture in an Aerated Rotating Biodisc Contactor

Synthetic wastewater containing 0–10% salt (NaCl) was treated in a rotating biodisc unit operating in continuous mode. Salt tolerant, Halobacter halobium-supplemented activated sludge culture was used in order to alleviate salt inactivation effects. Effects of important process variables such as inclusion of Halobacter, A/Q ratio, COD loading rate, and salt concentration on the COD removal rate and efficiency were investigated. The system performance improved with increasing A/Q ratio; however, it decreased with increasing COD loading rate and salt content. The liquid phase was aerated in order to keep suspended cells active at feed COD concentrations of 5,000 mg l −1. A mathematical model was developed to describe the system behavior. Model parameters were determined by using the experimental data. Salt inhibition was found to be significant for salt contents larger then 3% NaCl.

Anaerobic treatment of olive mill effluents

The anaerobic treatability of olive mill effluent was investigated using a laboratory scale upflow anaerobic sludge blanket reactor (UASBR) operated for about six months. The effects of various operating conditions including pH, feed strength and hydraulic retention time on the performance of the anaerobic treatment process were determined. In the first part of this study, the reactor was operated with feed COD concentrations from 5000 to 19,000 mg/l and a retention time of 1 day, giving organic loading rates from 5 to 18 kg COD/m3d. Soluble COD removal was around 75% under these conditions. In the second part of the study, feed CODs were varied from 15,000 to 22,600 mg/l while retention times ranged from 0.83 to 2 days; soluble COD removal was around 70%. A methane conversion rate of 0.35 m3 per kg COD removed was achieved during the study. The average volatile solids (VS) concentration in the reactor had increased from 12.75 g l−1 to 60 g l−1 by the end of the study. Sludge volume index (SVI) determinations performed to evaluate the settling characteristics of the anaerobic sludge in the reactor indicated excellent settleability with SVI values of generally less than 20 ml g−1. Sludge granules ranging from 3 to 8 mm in diameter were produced in the reactor. The second order substrate removal kinetics was applied by assuming that hydraulic conditions in the UASBR are approximately completely mixed and the model fitted well to the steady state operating results.

Anaerobic treatment of olive mill effluents

The anaerobic treatability of olive mill effluent was investigated using a laboratory scale upflow anaerobic sludge blanket reactor (UASBR) operated for about six months. The effects of various operating conditions including pH, feed strength and hydraulic retention time on the performance of the anaerobic treatment process were determined. In the first part of this study, the reactor was operated with feed COD concentrations from 5000 to 19,000 mg/l and a retention time of 1 day, giving organic loading rates from 5 to 18 kg COD/m 3 d. Soluble COD removal was around 75% under these conditions. In the second part of the study, feed CODs were varied from 15,000 to 22,600 mg/l while retention times ranged from 0.83 to 2 days; soluble COD removal was around 70%. A methane conversion rate of 0.35 m 3 per kg COD removed was achieved during the study. The average volatile solids (VS) concentration in the reactor had increased from 12.75 g l −1 to 60 g l −1 by the end of the study. Sludge volume index (SVI) determinations performed to evaluate the settling characteristics of the anaerobic sludge in the reactor indicated excellent settleability with SVI values of generally less than 20 ml g −1 . Sludge granules ranging from 3 to 8 mm in diameter were produced in the reactor. The second order substrate removal kinetics was applied by assuming that hydraulic conditions in the UASBR are approximately completely mixed and the model fitted well to the steady state operating results.

Effect of organic loading rate on anaerobic treatment of slaughterhouse wastewater in a fluidised-bed reactor

COD removed efficiencies in the range 75·0NDASH;98·9% were achieved in an anaerobic fluidised-bed reactor treating slaughterhouse wastewater, when evaluated at organic loading rates (OLR) of between 2·9 and 54·0 g COD/l.d, hydraulic retention times (HRT) of between 0·5 and 8 h and feed COD concentrations of between 250 and 4500 mg/l. More than 94% of feed COD could be removed up to OLR of about 27 g COD/l.d. Up to 0·320 litres of methane were produced per gram of COD removed and this methane production rate was independent of the OLR applied in this investigation. Volatile fatty acid (VFA) concentration in the reactor increased sharply at an OLR of about 30 g COD/l.d and, therefore, sufficient alkalinity should be provided to prevent pH from dropping to an undesirable level. The anaerobic fluidised-bed system can be operated at a significantly higher liquid throughput than other previously reported systems while maintaining its excellent efficiency.

Bioethanol production from dilute feedstock

Ethanol production from dilute feedstock of simulated and actual sugarcane mill wastewater was investigated by using the anaerobic entrapped yeast cell process. It was found that the ethanol productivity of 0.138×10 −4 g/liter void volume/h per unit volume of carrier could be achieved at the dilution rate 0.05 h −1 using actual sugarcane mill wastewater with the feed COD concenrations of 0.9–1.4 g/liter. Ethanol productivities of 0.225 × 10 −4 g/liter void volume/h per unit volume carrier and 2.31 × 10 −4 g/liter volume/h per unit volume of carrier could be achieved at the dilution rates of 0.075 and 0.20 h −1 with the feed COD concentrations of 2 and 6 g/liter, of simulated dilute feedstock, respectively. Based on the cost analysis of both maximum ethanol and methane productions from the dilute feedstock, the selection of the ethanol production is more beneficial than methane production for a period of longer than 8 years. The system provides an appropriate approach for pollution control, biofuel production, and treated wastewater reuse.

Palm oil refinery effluent treatment by sequencing batch reactors

With the advances made in solenoid valves, sensors and microprocessor controllers, sequencing batch treatment technology can now be further developed and conveniently applied to wastewater treatment. Sequencing batch reactors (SBR), in contrast to conventional activated sludge plants, allow the control of reaction time for bioxidation of the organic substrates and maintenance of the necessary level of biomass in the reactor to be accomplished with a single tank. Bench-scale and pilot-scale studies were carried out, using palm oil refinery effluent having BOD and COD concentrations of up to 800 mg litre −1 and 1500 mg litre −1 , respectively, to assess the treatability of palm oil refinery effluent by SBR. A microprocessor controller was used to control the various SBR operating modes. Results indicate good BOD and COD removals and process stability under wide variations of feed BOD and COD concentrations.

Performance evaluation of the anaerobic fluidised bed system: II. Biomass holdup and characteristics

AbstractThe biomass holdup and characteristics of the anareobic fluidised bed system for methane recovery from liquid wastes was examined at COD loadings of between 5.8 to 108 kg m−3 day,−1 hydraulic retention times of between 0.45 to 8h, and feed COD concentrations of between 480 to 9000 mg dm−3. Under these operating conditions, the equilibrium biomass holdups increased with increasing COD loadings and varied from 15000 to 32000 mg VSS dm−3 The distribution of biomass holdup and biofilm thickness in the reactor was relatively uniform, because of the completely mixed conditions maintained and the continuous sloughing of biofilms induced by the effervescence caused by rising methane bubbles. This continuous biofilm sloughing process also eliminated the need for intentional sludge wasting and consequently, the resulting sludge retention time in the reactor decreased with increasing COD loadings. The ability of the anaerobic fluidized bed system to retain a high biomass holdup was clearly demonstrated. As a result this system is ideal for being employed as a high‐rate system for methane recovery from liquid wastes, even at low feed COD concentrations.

Performance evaluation of the anaerobic fluidised bed system: I. Substrate utilisation and gas production

AbstractCOD removal efficiencies in the range 75 to 98% were achieved in an anaerobic fluidised bed system designed for the recovery of methane from liquid wastes, when evaluated at COD loadings of between 5.8 to 108 kg m−3 day−1, hydraulic retention times of between 4.45 to 8 h, and feed COD concentrations of beween 480 to 9 000 mg dm−3. More than 90% of feed COD could be removed up to COD loadings of about 40 kg m−3 day−1. Up to around 300 dm2 of methane were produced per kg COD removed and this methane production rate was independent of the COD loadings applied in this investigation. Volatile acid concentration in the reactor increased sharply at a COD loading of about 40 kg m−3 day−1 and therefore, sufficient alkalinity should be provided to prevent pH from dropping to the undesirable level. The anaerobic fluidised bed system can be operated at a significantly higher liquid throughputs while maintaining its excellent efficiency.