5-day Carbonaceous Biochemical Oxygen Demand Research Articles

Impact of various aeration strategies on the removal of micropollutants and biological effects in aerated horizontal flow treatment wetlands

Two aerated horizontal subsurface flow treatment wetlands were studied over two years for the removal efficacy with respect of conventional wastewater parameters, micropollutants and effect-based methods. One wetland served as control and was aerated 24 h d−1 across 100% of the fractional length of the system. The second aerated horizontal flow treatment wetland was investigated under several aeration modes: first year with a zone of 85% aeration, followed by five months with a zone of 50% aeration and six months with a zone of 35% aeration. With 85% aeration, no significant difference in the removal efficacy as compared to the fully aerated control could be observed, except for E. coli, which were removed four times better in the control. No significant difference in removal efficacy for Total Organic Carbon, 5-day Carbonaceous Biochemical Oxygen Demand, caffeine, and naproxen were observed. A 50% non-aerated zone reduced the overall removal efficacy of biological effects. The highest removal efficacy for the moderately biodegradable micropollutants benzotriazole and diclofenac was observed in the system with 50% aeration. This could be due to the sharp increase of dissolved oxygen (DO) and oxidation reduction potential at the passage from the non-aerated to the aerated zone (at 75% of the fractional length). The internal concentration profiles of caffeine, ibuprofen and naproxen varied from 12.5%, 25%, 50% to 75% fractional length due to redox shift, DO variations and other conditions. A reduction of the aerated zone to 35% of the fractional length results in reduced treatment efficacy for benzotriazole, diclofenac, acesulfame and biological effects but 50% aeration yielded as much degradation as the fully aerated control. These results indicate that less aeration could provide similar effluent water quality, depending on the pollutants of interest. E. coli and biological effects were removed best in the fully aerated system.

Assessment of a Soft Sensor Approach for Determining Influent Conditions at the MWRDGC Calumet WRP

AbstractMany older water reclamation plants (WRPs) are implementing model-based process control to satisfy increasingly stringent effluent requirements while they lower energy costs, but these methods require reliable process information. Soft sensors can help to provide such information by building on easily acquirable and historical data. In this investigation of a soft-sensor approach at a conventional WRP, many historical data were missing, which suggested that a large fraction of the information would be lost if the missing data were not well managed. This study applied an iterated stepwise multiple linear regression (ISMLR) approach to minimize the loss of data and to predict real-time influent ammonia and CBOD5 (5-day carbonaceous biochemical oxygen demand), and future influent flow at the Metropolitan Water Reclamation District of Greater Chicago (MWRDGC) Calumet WRP. Relative to a simple deletion method (which retained about 45% of the daily data), the ISMLR approach successfully retained substan...

Effect of copper on the growth of shrimps Litopenaeus vannamei: water parameters and copper budget in a recirculating system

Shrimps (Litopenaeus vannamei) were intensively cultured in a recirculating aquaculture system for 98 days to investigate effects of 0.3 mg/L Cu on its performance, Cu budget, and Cu distribution. Shrimps in Cu-treated systems had greater mean final weight (11.10 vs 10.50 g), body length (107.23 vs 106.42 mm), survival rate (67.80% vs 66.40%), and yield (6.42 vs 5.99 kg/m3), and lower feed conversion ratio (1.20 vs 1.29) than those in control systems but the differences were not significant. Vibrio numbers remained stable (104–106 colony forming units/mL) in the rearing tanks of both control and treated systems. Total ammonium-N, nitrite-N, nitrate-N, pH, chemical oxygen demand, 5-day carbonaceous biochemical oxygen demand, and total suspended solids were similar in controls and treatments. Dissolved Cu concentration in the treated systems decreased from 0.284 to 0.089 mg/L while in the control systems it increased from 0.006 2 to 0.018 mg/L. The main sources of Cu in the treated systems were the artificially added component (75.7% of total input), shrimp feed (21.0%), water (2.06%), and shrimp biomass (1.22%). The major outputs of Cu occurred via the mechanical filter (41.7%), water renewal (15.6%), and draining of the sediment trap (15.1%). The foam fractionator removed only 0.69% of total Cu input. Harvested shrimp biomass accounted for 11.68% of Cu input. The Cu concentration of shrimps in the Cu-treated systems (30.70 mg/kg wet weight) was significantly higher than that in control systems (22.02 mg/kg). Both were below the maximum permissible concentration (50 mg/kg) for Cu in seafood for human consumption in China. Therefore, recirculating systems can be used for commercial on-growing of Litopenaeus vannamei without loss of shrimp quality, even in water polluted by 0.30 mg/L Cu. The mechanical filter is the main route for Cu removal.

Combined anaerobic-aerobic and UV/H2O2 processes for the treatment of synthetic slaughterhouse wastewater

The biological treatment of a synthetic slaughterhouse wastewater (SSWW) is studied using an anaerobic baffled bioreactor (ABR) and an aerobic activated sludge (AS) at a laboratory scale in continuous mode. The total organic carbon (TOC) loading rate, the total nitrogen (TN) loading rate, and the flow rate are 0.03–1.01 g/(L.day), 0.01–0.19 g/(L.day), and 2.93–11.70 mL/min, respectively. The results reveal that combined anaerobic-aerobic processes had higher efficiency to treat SSWW than a single process. Up to 96.36% TOC, 80.53% TN, and 99.38% 5-day carbonaceous biochemical oxygen demand (CBOD5) removal from an influent concentration of 1,009 mgTOC/L, 420 mgTN/L, and 640 mgCBOD5/L at the hydraulic retention time (HRT) of 6.24 days and a flow rate of 3.75 mL/min are achieved. The UV/H2O2 process is studied to treat a secondary effluent of SSWW with TOC loadings of 65–350 mg/L. Up to 75.22% TOC and 84.38% CBOD5 removal are obtained at the HRT of 3 h with H2O2 concentration of 900 mg/L. Optimum molar ratios of 13.87 mgH2O2/mgTOCin and 4.62 mgH2O2/mgTOCin.h are also obtained. Combined anaerobic-aerobic and UV/H2O2 processes enhanced the biodegradability of the TOC, TN, and CBOD5 present in the SSWW. Up to 99.98% TOC, 82.84% TN, and 99.69% CBOD5 overall removals are obtained for an influent concentration of 1,005 mgTOC/L, 200 mgTN/L, and 640 mgCBOD5/L at the HRT of 4 days and a flow-rate of 5.90 mL/min.

Slaughterhouse wastewater treatment by combined anaerobic baffled reactor and UV/H 2O 2 processes

Combined processes of biological anaerobic baffled reactor (ABR) and UV/H 2O 2 at a laboratory scale were studied to treat a synthetic slaughterhouse wastewater. In this study, the total organic carbon (TOC) loadings of 0.2–1.1 g/(L day) were used. The results revealed that combined processes had a higher efficiency to treat the synthetic slaughterhouse wastewater. Up to 95% TOC removal was obtained for an influent concentration of 973.3 mgTOC/L at the hydraulic retention time (HRT) of 3.8 days in the ABR and 3.6 h in the UV photoreactor. Meanwhile, up to 97.7% and 96.6% removal of chemical oxygen demand (COD) and 5-day carbonaceous biochemical oxygen demand (CBOD 5) were observed in the ABR for the same influent concentration, respectively. Comparatively, for an influent concentration of 157.6 mgTOC/L, the UV/H 2O 2 process alone with the TOC loading of 0.06–1.9 g/(L h) was also studied, in which, up to 64.3%, 83.7%, and 84.3% of TOC, COD, and CBOD 5 removal were observed, respectively, at the HRT of 2.5 h with hydrogen peroxide (H 2O 2) concentration of 529 mg/L. It was found that individual ABR and UV/H 2O 2 processes enhanced the biodegradability of the treated effluent by an increased CBOD 5/COD ratio of 0.4 to 0.6. An optimum H 2O 2 dosage of 3.5 (mgH 2O 2)/(mgTOC in h) was also found for the UV/H 2O 2 process.

Effects of two commercially available low-protein diets (21% and 31%) on water and sediment quality, and on the production of Litopenaeus vannamei in an outdoor tank system with limited water discharge

Effects of feeding Litopenaeus vannamei with commercial low-protein diets on shrimp performance and on water and sediment quality were studied under high shrimp density with limited water discharge. Twelve tanks (each 10.5 m 2) were stocked with juvenile shrimp (average weight, 1.69 g) at a density of 40/m 2. Shrimp in six tanks were fed a 21% protein diet, and shrimp in the other six tanks were fed a 31% protein diet. Selected water quality parameters were monitored over a 94-day period. Shrimp growth, survival, feed conversion ratio (FCR) and selected sediment quality parameters were evaluated at harvest. Shrimp survival was significantly higher ( P=0.041) in the 31% treatment (96.2%) than in the 21% treatment (90.6%). Mean final weight of the shrimp in the 31% treatment (14.04 g) also was significantly higher ( P<0.001) than in the 21% treatment (12.17 g). The FCR of the shrimp in the 31% treatment (1.75) was significantly lower ( P<0.001) than in the 21% treatment (2.15). The gross production of the 31% treatment (540 g/m 2) was 22% higher than that of the 21% protein diet (441 g/m 2). No significant differences were found between the 21 and 31% treatments in the daily-measured water quality parameters (dissolved oxygen, temperature, pH, Secchi readings, and salinity) and the weekly-measured parameters (total ammonia-N, nitrite-N, nitrate-N, reactive and total phosphorus, 5-day carbonaceous biochemical oxygen demand (cBOD 5), chemical oxygen demand (COD), total suspended solids and volatile suspended solids (VSS)). Differences in sediment quality parameters (volume of sediment, COD, cBOD 5 and VSS) between treatments were not statistically significant. This work shows that the 31% protein diet provided better production results than the 21% protein diet, yet it did not significantly deteriorate the water or sediment quality.

Start-Up Performance of a Subsurface-Flow Constructed Wetland for Domestic Wastewater Treatment

Constructed wetlands have been shown to provide sufficient domestic wastewater treatment in temperate climates. However, the effectiveness of this technology, when subjected to severe temperature extremes during start-up conditions, is limited. Because of the growing interest in constructed wetland technology within smaller communities located in colder-climates, and the need for cost-effective treatment systems, this paper presents the performance of a constructed wetland system during the first two-years of operation under a variety of loading and operating conditions associated with northern climates. While the treatment performance of constructed wetland systems has been widely documented within the literature, documentation on performance during start-up stages has been limited. The results indicate that effective and sufficient constructed wetland seasonal removals of total suspended solids, volatile suspended solids, 5-day carbonaceous biochemical oxygen demand, chemical oxygen demand, and fecal coliform were achieved within the wetland cell during the first two-years of operation. Wastewater temperatures appeared to affect 5-day carbonaceous biochemical oxygen demand and chemical oxygen demand removal rates. Nitrogen and phosphorus reductions were not as effective and varied seasonally, as well as with wastewater temperature.

Batch coagulation of a lagoon for fecal coliform reductions

The research examined the factors affecting fecal coliform removal from lagoon wastewater by batch treatment with aluminum sulphate. Laboratory experiments based on factorial designs and jar tests were used to determine the statistically significant factors controlling the removal of fecal coliform bacteria. Temperature, chemical dose, pH, rapid mixing and flocculation were examined at two different laboratory scales. The results indicated that alum dose and pH were the only significant parameters. A design chart was developed for the wastewater tested enabling dose determination for a desired fecal coliform reduction. This chart was used to select the dose for a full scale field trial to reduce fecal coliforms to < 10 per 100 ml. The design dose was 300 mg 1 −1 Al 2(SO 4) 3·18 H 2O and a final pH of 6.4 was predicted. The field trial used liquid alum (Al 2(SO 4) 3·14.2 H 2O) delivered by tanker truck and distributed by motor boat. The treatment reduced fecal coliforms by 99.9%, total phosphorus by 97%, total suspended solids (TSS) by 90% and 5-day carbonaceous biochemical oxygen demand (CBOD 5) by 35%. The cost of treatment for labour and materials was $CDN 0.07 m −3.