Co-treatment of domestic and dairy wastewater in an activated sludge system.

This research assesses the potential for co-treatment of a dairy wastewater with a domestic wastewater in a lab-scale, continuous-flow, activated sludge system. To evaluate the influence of the dairy waste contribution, seven runs were conducted with each run being a mixture of dairy wastewater (either cheese or milk) in different ratios ranging from 1:0.01 to 1:0.30 by volume. More than 87% of the carbon was removed for both waste additions; however, while 95% ammonia-nitrogen removal was recorded for the cheese waste, only 75% removal was obtained for the milk. Kinetic studies for carbon consumption revealed a first-order model with lower kinetic constants as the cheese waste proportion increased. Specific carbon consumption rates indicated that the biomass had not reached its maximum potential to degrade carbon. The ability of the biomass to settle was hindered when the Gram negative to Gram positive filamentous bacteria ratio increased to approximately 1.5.

Treatment of a slaughterhouse wastewater: effect of internal recycle rate on chemical oxygen demand, total Kjeldahl nitrogen and total phosphorus removal.

This study investigated the ability of an anaerobic/anoxic/oxic (A2/O) system to treat a slaughterhouse wastewater. The system employed two identical continuous-flow reactors (101 total liquid volume each) running in parallel with the main operational variable, being the internal recycle (IR) rate. The chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN) and total phosphorus (TP) performance was evaluated as the IR flowrate was increased from a Q of 151d(-1) to 4Q at a system hydraulic retention time of 16 h and a solids retention time of 10 d. The COD:TKN and COD:TP ratios were 8.2:1 and 54:1, which supported both nitrogen and phosphorus removal. For all IR multiples of Q, the COD removal was in excess of 90%. The TKN removal showed a modest improvement (a 4-5% increase, depending on the dissolved oxygen (DO)) as the IR doubled from Q to 2Q, but no further increase was observed at the 4Q IR rate. The TP removal reached its optimum (around 85%-89% (again depending on the DO)) at the 2Q rate.

Treatment of four industrial wastewaters by sequencing batch reactors: evaluation of COD, TKN and TP removal.

This study investigated the ability of a sequencing batch reactor (SBR) system to treat four industrial wastewaters, namely, textile, landfill leachate, seafood and slaughterhouse effluents. The system employed three identical SBRs (10 l volume each) operating in parallel and each waste was treated one at a time. The operational variables examined included the length of the non-aerated period and the solids retention time (SRT). All four wastewaters experienced chemical oxyfen demand (COD) and total kjeldhal nitrogen (TKN) removals greater than 81%, while the TP removals were lower, ranging from 57 to 94%. The length of the non-aerated period appeared to have minimal effect on the SBR performance; however, increases in SRT reduced the percent TP removal for the textile and leachate wastes only. In addition, to investigate organic loading limits to the seafood SBR system, the COD was increased by three increments of 250 mg l(-1) starting from a baseline concentration of 1100 mg l(-1). This resulted in a reduction in both the TKN and TP removal at the higher concentrations. Finally, for the slaughterhouse wastewater, the COD:TKN ratio was tested at levels of 6:1, 8:1 and 9:1 with the result that only the TP removal was affected at the lowest ratio.

The influence of organic loading and anoxic/oxic times on the removal of carbon, nitrogen and phosphorus from a wastewater treated in a sequencing batch reactor.

In this study, 10 L sequencing batch reactors (SBRs) were operated at a 12-h cycle length (four alternating anoxic/oxic conditions) to assess the biological nutrient removal potential of a domestic wastewater treated at the Huay Kwang plant, Bangkok, Thailand. The wastewater was found to be carbon-limited (chemical oxygen demand (COD) to total Kjeldahl nitrogen (TKN) (i.e., COD:TKN) ratio of 6.4:1). This ratio was insufficient to support good phosphorus removal. Glucose was therefore added to increase the COD:TKN ratio ultimately to 10:1 and the COD, TKN and total phosphorus (TP) removals at this ratio were all in excess of 95%. An alternative carbon source from a local fruit canning industry was then added at the same COD:TKN ratio; and, in order to increase the throughput of the waste treated, the cycle length was simultaneously shortened to 8 h keeping approximately the same anoxic/oxic fractions. The COD removal remained high (> 95%), however the TKN and TP removals were substantially reduced (79% and 66%, respectively), indicating that the shortened cycle length was sub-optimum. The last phase of the research involved changing the anoxic/oxic fractions of the cycle time to maximize performance. It was found that for the conditions studied in this research, the performance improved in proportion to the increase in the first anoxic fraction, being most stable at the highest anoxic fraction of the cycle length (0.33).

Treatment of a textile dye wastewater by an electrochemical process.

This study explored the effectiveness of an electrochemical process to treat a sulfur dye wastewater from a textile industry. The treatment system included a 4.0 L reactor equipped with five steel electrode plates, and a separate sedimentation tank of equal liquid volume. The experimental part involved two distinct, sequential stages. In the first stage, the effect of initial pH and electrical charge (i.e., current times reaction time) on the treatment process was explored. Experiments were conducted in a factorial mode, involving three initial pH values (3, 4 and 5), and six electrical charges (ranging from 150 to 1,350 coulomb), respectively. Results indicated that chemical oxygen demand (COD), total suspended solids (TSS), and color removal efficiency improved with a decrease in initial pH and an increase in electrical charge. Overall, high percent removal values were observed ranging from 63% to 80% for COD, 81% to 96% for TSS, and 93% to 99% for color. During the second stage, the electrode corrosion pattern was investigated for a period of 45 days. Under stable operating conditions, electrode consumption was found to conform to Faraday's law. Moreover, process performance regarding COD, TSS, and color reduction was comparable to that obtained in the first stage of the study.