Optimum Chemical Oxygen Demand Research Articles

Treatment of olive mill wastewater by the combination of ultrafiltration and bipolar electrochemical reactor processes

The main purpose of this study was to investigate the removal of the chemical oxygen demand (COD) from olive mill wastewater (OMW) by the combination of ultrafiltration with electrocoagulation process. Ultrafiltration process equipped with CERAVER membrane was used as pre-treatment for electrochemical process. The obtained permeate from the ultrafiltration process allowed COD removal efficiency of about 96% from OMW. Obtained permeate with an average COD of about 1.1 g dm −3 was treated by electrochemical reactor equipped with a reactor with bipolar iron plate electrodes. The effect of the experimental parameters such as current density, pH, surface electrode/reactor volume ratio and NaCl concentration on COD removal was assessed. The results showed that the optimum COD removal rate was obtained at a current density of 93.3 A m −2 and pH ranging from 4.5 to 6.5. At the optimum operational parameters for the experiments, electrocoagulation process could reduce COD from 1.1 g dm −3 to 78 mg dm −3, allowing direct discharge of the treated OMW as that meets the Algerian wastewater discharge standards (<125 mg dm −3).

Organics removal from dairy wastewater by electrochemical treatment and residue disposal

Dairy industry wastewater is characterized by high chemical oxygen demand (COD) and other pollution load. In the present study, the treatment of simulated dairy wastewater (SDW) was performed by electrochemical (EC) method using iron electrode. Full factorial central composite design (CCD) with four factors namely current density ( J), dosage of sodium chloride (NaCl) ( m), electrolysis time ( t) and pH, with each factor at five levels, was used to optimize the factors for higher COD removal. Operational parameters J, m, t and pH were varied between 61.73–308.64 A/m 2, 0–2 g/l, 10–90 min and 5–11, respectively. Optimum value of J, t and pH were found 270 A/m 2, 50 min, and 7.0, respectively, while m was found to be zero. Optimum COD removal efficiency was found to be ≈70%. Physico-chemical analysis of iron electrodes and residues (scum and sludge) has been carried out to understand the EC mechanism as well as to study the disposal aspect of the residues generated during EC treatment. The mechanism of COD removal by EC seems to be a combination of electro-coagulation, electro-floatation and electro-oxidation.

Hydrogen production from glucose-containing wastewater using an anaerobic sequencing batch reactor: Effects of COD loading rate, nitrogen content, and organic acid composition

In this work, the process performance of an anaerobic sequencing batch reactor (ASBR) for the hydrogen production from glucose-containing wastewater was studied. The anaerobic sludge taken from a brewery wastewater-treating anaerobic unit was pretreated by boiling for 15 min before being added into the ASBR unit as the seeding sludge. The ASBR unit was operated at a temperature of 37 °C, a hydraulic reaction time (HRT) of 24 h, and different chemical oxygen demand (COD) loading rates from 10 to 50 kg m −3 d −1 without and with pH control at 5.5. The results showed that at the optimum COD loading rate of 40 kg m −3 d −1 and pH 5.5, the produced gas was found to contain 44% H 2 and 56% CO 2, and no methane in the produced gas was detected at all operating conditions. At these optimum conditions, the highest hydrogen yield was 1.46 mol H 2/mol glucose consumed. Additionally, the main organic components in the liquid effluent were acetic and butyric acids. Under the optimum COD-to-nitrogen (COD:N) ratio of 100:2.4, the system with pH controlled at 5.5 gave the highest specific H 2 production rate of 7.44 l H 2 l −1 d −1, corresponding to the highest butyric acid to acetic acid ratio.

EFFECTS OF SHOCK 2,4‐DICHLOROPHENOL (DCP) AND COD LOADING RATES ON THE REMOVAL OF 2,4‐DCP IN A SEQUENTIAL UPFLOW ANAEROBIC SLUDGE BLANKET/AEROBIC COMPLETELY STIRRED TANK REACTOR SYSTEM

The treatability of 2,4‐dwichlorophenol (DCP) was studied in an anaerobic/aerobic sequential reactor system. Laboratory scale upflow anaerobic sludge blanket (UASB) reactor/ completely stirred tank reactors (CSTR) were operated at constant 2,4‐DCP concentrations, and increasing chemical oxygen demand (COD) loading rates. The effect of shock organic loading rates on 2,4‐DCP, COD removal efficiencies and methane gas production were investigated in the UASB reactor. When the organic loading rate was increased from 3.6 g l−1 d−1 to 30.16 g l−1 d−1, the COD and 2,4‐DCP removal efficiencies decreased from 80 to 25% and from 99 to 60% in the UASB reactor. The optimum organic loading rates for maximum 2,4‐DCP (E=99–100%) and COD (E=65–85%) removal efficiencies were 25–30 and 8–20 g‐COD l−1 d−1, respectively. The percentage of methane of the total gas varied between 70 and 80 while the organic loadings were 18 g‐COD l−1 d−1 and 20.36 g‐COD l−1 d−1, respectively. During 80 days of operation, 2,4‐DCP concentration was found to be below 0.5 and 0.1 mg l−1 in aerobic reactor effluent resulting in 78 and 100% removal efficiencies. When the hydraulic retention time (HRT) was 18.72 h, the 2,4‐DCP removal efficiency was 97% in the aerobic reactor. The optimum COD removal efficiency was 78.83% in anaerobic reactor effluent at an influent COD loading rate of 7.238 g‐COD l−1 d−1 while 83.6% maximum COD removal efficiency was obtained in the aerobic reactor, resulting in a total COD removal efficiency of 96.83% in the whole system. The 2,4‐DCP removal efficiency was 99% in the sequential anaerobic (UASB)/aerobic (CSTR) reactor system at COD loading rates varying between 11.46 and 30.16 g‐COD l−1d−1.

Assessment of the efficiency and economic viability of various methods of treatment of sanitary landfill leachate

This study assesses the efficiency of various physico-chemical, biological and other tertiary methods for treating leachate. An evaluation study on the treatability of the leachate from methane phase bed (MPB) reactor indicated that at an optimum hydraulic retention time of 6 days, the efficiency of the reactor in terms of biological oxygen demand (BOD) and chemical oxygen demand (COD) removal was 91.29 and 82.69%, respectively. Recycling of the treated leachate through the municipal solid waste layers in the leachate recycling unit (LRU) resulted in a significant increase in the biodegradation of organics present in the leachate. Optimum BOD and COD removal efficiencies were achieved at the third recycle; additional recycling of the leachate did not produce any significant improvement. Physico-chemical treatment of the leachate demonstrated that alum and lime (Option 2) were more economical than coagulants lime and MgCO(3). A cost analysis of the economics of the various treatments revealed that the alternative treatment consisting of a MPB bed followed by a LRU and aerated lagoon is the most cost-effective treatment. However, the alternative consisting of a MPB followed by the LRU and a soil column, which is slightly more costly, would be the most appropriate treatment when adequate land is readily available.

Characterization of aerobic granules by microbial density at different COD loading rates

Aerobic granules were cultivated under temporal alternating aerobic and anoxic conditions without the presence of a carrier material in a sequencing batch reactor (SBR) with a high column height/column diameter ratio. The reactor was operated for 6 h per cycle (aerobic: 4.75 h, anoxic: 1.25 h). To determine a new parameter for the definition of aerobic granules, a protocol of 4,6-diamidino-2-phenylindole hydrochloride staining and fluorescence image processing was developed. The d tm analysis showed that the increase in the chemical oxygen demand (COD) loading rate promoted no more growth of the aerobic granules. It was inconsistent with the results of the analysis of the sludge volume index (SVI) value but matched well with the results of the COD and nitrogen removal of the SBR and the particle size distribution by LS-PSA. The optimum COD loading rate for aerobic granulation in the SBR was 2.52 kg/m 3 d. When d tm was correlated with the biomass concentration and the SVI value during the period of granule formation, d tm could be used as a more sensitive and accurate parameter for classifying aerobic granules and optimizing the operational conditions for aerobic granulation processes.

Efficiency of the Coagulation-Flocculation Method for the Treatment of Dye Mixtures Containing Disperse and Reactive Dye

Abstract The coagulation-flocculation method was used to treat aqueous solutions containing varying ratios of commercial disperse and reactive dyes. The effectiveness of this method was assessed using such coagulants as alum, polyaluminium chloride (PACl) and MgCl2, and an anionic coagulant aid. The jar test method was used to measure the effects of pH and coagulant type and dosage on colour removal and chemical oxygen demand (COD) reduction. The effect of coagulant aid on floc settling time was also measured. The results showed that the coagulant dosage needed to achieve optimum colour removal and COD reduction increased as the percentage of reactive dye in the mixture increased. Alum and PACl performed effectively in a lower pH range (pH 3.8 to 5.2), whereas MgCl2 performed effectively in a higher pH range (pH 10.4 to 10.9). PACl was more effective than MgCl2 and alum, achieving &amp;gt;99% colour removal and 96.3% COD reduction using a smaller quantity of the coagulant. The addition of coagulant aid improved floc settling time. These results show that PACl is more effective than MgCl2 and alum in removing both colour and COD in the treatment of the industrial textile wastewater samples.

Ozone disintegration of excess biomass and application to nitrogen removal.

A pilot-scale facility integrated with an ozonation unit was built to investigate the feasibility of using ozone-disintegration byproducts of wasted biomass as a carbon source for denitrification. Ozonation of biomass resulted in mass reduction by mineralization as well as by ozone-disintegrated biosolids recycling. Approximately 50% of wasted solids were recovered as available organic matter (ozonolysate), which included nonsettleable microparticles and soluble fractions. Microparticles were observed in abundance at relatively low levels of ozone doses, while soluble fractions became dominant at higher levels of ozone doses in ozone-disintegrated organics. Batch denitrification experiments showed that the ozonolysate could be used as a carbon source with a maximum denitrification rate of 3.66 mg nitrogen (N)/g volatile suspended solids (VSS) x h. Ozonolysate was also proven to enhance total nitrogen removal efficiency in the pilot-scale treatment facility. An optimal chemical oxygen demand (COD)-to-nitrogen ratio for complete denitrification was estimated as 5.13 g COD/g N. The nitrogen-removal performance of the modified intermittently decanted extended aeration process dependent on an external carbon supply could be described as a function of solids retention time.

Optimal organics removal in sand beds, treating industrial influent

Abstract Much interst has been taken during the last decade in finding methods alternative to the usual treatment method. Wastewater application on sand is often acceptable alternative. In this study, sand beds were used in treating a beer ‐ factory influent for organic content removal based upon the chemical oxygen demand(COD). Optimum COD removal percentages were found to be 90 to 96% for sand depth and applied influent COD concentrations of 61 to 82.5 cm and 1550 to 2125 mg/l, respectively. Prediction models of the bed ‐ COD removal percentage in terms of sand depth and influent concentration were determined.