Reuse and recovery of raw hospital wastewater containing ofloxacin after photocatalytic treatment with nano graphene oxide magnetite.

Inadequate treatment of hospital wastewater could result in considerable risks to public health due to its macro- and micropollutant content. In order to eliminate this problem, a new nanoparticle composite was produced under laboratory conditions and a photocatalytic degradation approach was used. Chemical oxygen demand (COD), biological oxygen demand (BOD5), total suspended solids (TSS), total Kjeldahl nitrogen (TKN), total phosphorus (TP) (macro) and oflaxin (micro) pollutant removal were investigated with the nano graphene oxide magnetite (Nano-GO/M) particles by two different processes, namely adsorption and photodegradation. Low removal efficiencies (21-60%) were obtained in the adsorption process for the parameters given above, after 90 min contact time at a pH of 7.8 with 5 g/L Nano-GO/M composite. Using the photodegradation process, higher removal efficiencies were obtained with 2 g/L Nano-GO/M composite for COD (88%), TSS (82%), TKN (95%) and oflaxin (97%), at pH 7.8 after 60 min irradiation time at a UV power of 300 W. The synthesized nanoparticle was reused for two sequential treatments of pharmaceutical wastewater with no significant losses of removal efficiencies (for oflaxin 97%-90%). The quality of the treated hospital wastewater was first class according to the Turkish Water Pollution Control Regulations criteria. This water could also be used for irrigation purposes.

Comparison of the sensitivities of fish, Microtox and Daphnia-magna bioassays to amoxycillin in anaerobic/aerobic sequential reactor systems.

In this study the anaerobic treatability of amoxycillin (AMX) was investigated in a laboratory-scale anaerobic multi-chamber bed reactor (AMCBR)/aerobic continuously stirred tank reactor (CSTR) system. The chemical oxygen demand (COD) and AMX removal efficiencies were around 94% in the AMCBR reactor at hydraulic retention times (HRTs) between 2.25 and 5.5 days. Decreasing the HRT appeared not to have a significant effect on the performance of the AMCBR up to a HRT of 1.13 days. The maximum methane production rate and methane percentage were around 1,100-1,200 mL/day and 55%, respectively, at HRTs between 2.25 and 5.5 days. The decrease in HRT to 1.5 days decreased slightly the gas productions (1,000 mL/day and 500 mL for total and methane gases) and methane percentage (45%). The AMCBR recovered back to its baseline performance within a couple of days. The acute toxicity of 150 mg/L AMX was monitored with Daphnia magna, Lepistes sp., and Vibrio fischeri acute toxicity tests. The acute toxicity removals were 98, 96 and 96% for V. fischeri, D. magna and Lepistes sp. in the effluent of the sequential system treating 150 mg/L AMX at HRTs of 2.25-5.5 days. Among the trophic organisms used in the acute toxicity tests the most sensitive organism was found to be bacteria (V. fischeri) while the most resistant organism was found to be fish (Lepistes sp.).

Effects of sludge retention time and biosurfactant on the treatment of polyaromatic hydrocarbon (PAH) in a petrochemical industry wastewater.

A laboratory-scale aerobic activated sludge reactor (AASR) system was employed to investigate the effects of sludge retention time (SRT) on the removal of three polyaromatic hydrocarbons (PAHs) with low benzene rings [(acenaphthene (ACT), fluorene (FLN) and phenanthrene (PHE)] and six PAHs with high benzene rings [(benzo[b]fluoranthene (BbF), benzo[k]fluoranthene (BkF), benzo[a]pyrene (BaP), indeno[1,2,3-cd]pyrene, dibenz[a,h]anthracene (DahA), benzo[g,h,i]perylene (BghiP)] in the presence of rhamnolipid (RD), emulsan (EM) and surfactine (SR) biosurfactants. This study showed that biosurfactants enhance the PAH biodegradation by increasing the biomass growth. RD exhibits a better performance than the other biosurfactants in the removal of the chemical oxygen demand (COD) and PAHs. At a RD concentration of 15 mg/L aerobic treatment for 25 days, SRT was enough to remove over 95% of total PAHs, and COD(dis). Under the same conditions 75% of COD originating from the inert organics (COD(inert)) and 96% of COD originating from the inert soluble microbial products (COD(imp)) were removed. At 25 days SRT and 15 mg/L RD concentration, about 88% of PAHs were biodegraded by the AASR system, 4% were accumulated in the system, 3% were released in the effluent, and 5% remained in the waste sludge.

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(-1) d(-1).

Sequential anaerobic, aerobic/anoxic treatment of simulated landfill leachate.

In this study COD, ammonia and nitrate were treated through methanogenesis, nitrification denitrification and anammox processes in anaerobic-aerobic and anaerobic/anoxic sequential in leachate samples produced from municipal solid waste in an anaerobic simulated landfilling bioreactor. The experiments were performed in an upflow anaerobic sludge blanket reactor (UASB), aerobic completely stirred tank reactor (CSTR) and upflow anaerobic/anoxic sludge blanket reactor (UA/A(N)SB). Hydraulic retention times in anaerobic, aerobic and anaerobic/anoxic stages were 1, 3.6 and 1 days, respectively, through 244 days of total operation period with 168 days of adaptation period of microorganisms to the reactors. The organic loading rates increased from 5.9 to 50 kg COD m(-3) day(-1). The total COD and TN removal efficiencies of the anaerobic-aerobic-anoxic system were 96% and 99%, respectively, at an influent OLR as high as 50 kg COD m(-3) day(-1). The maximum methane percentage in the UASB reactor was 82% while the methane percentage was zero in UA/A(N)SB reactor for the aforementioned OLR at the end of steady-state conditions. NH4-N removal efficiency of the aerobic reactor was 90% while anaerobic ammonia oxidation was measured as 99% in the anoxic reactor. The denitrification efficiency was 99% in the same reactor. Total TN removal of the whole system was 99%.

Effects of hydraulic retention time (HRT) and sludge retention time (SRT) on the treatment of nitrobenzene in AMBR/CSTR reactor systems.

The effect of hydraulic retention time (HRT) and solid retention time (SRT) on the biodegradation of a synthetic wastewater containing nitrobenzene was investigated in a sequential anaerobic migrating blanket reactor (AMBR) and aerobic completely stirred tank reactor (CSTR) system. Reactor performance was evaluated at six different HRTs (1,1.5,2,2.5,3.5,5.19 and 10.38 days) and at six different SRTs (32,53,76,217,415 and 932 days). The influent COD and nitrobenzene concentration were kept constant at 3000 mg l(-1) and 60 mg l(-1), respectively, during continuous operation. The maximum COD removal efficiency was found to be 92% at a HRT of 10.38 days and a SRT of 932 days in AMBR reactor. However, nitrobenzene removal efficiencies were found to be 99.9% through all HRTs and SRTs in AMBR reactor. Most of the influent COD and nitrobenzene concentrations were removed in first compartment of AMBR. The total and methane gas production rates increased from 2760 ml day(-1) to 11760 ml day(-1) and from 1300 ml day(-1) to 3331 ml day(-1), respectively, as the HRT was decreased from 10.38 to 1 day in AMBR. However, methane percentage decreased from 47% to 28% with decreased HRTs and SRTs. The methanogens inhibition was observed at lower HRTs. pH values in the compartments and the effluent of AMBR was between optimum values. TVFA concentrations in effluent of AMBR were measured as zero until a HRT of 3.5 days. In the aerobic CSTR reactor, the COD removal efficiency decreased from 79% to 68% with decreased HRT from 6.79 to 0.67 days. It was found that the nitrobenzene transformed to aniline under anaerobic phase, and then the aniline mineralized in the oxidative stage, with efficiencies varying between 79% to 99.9%, in anaerobic/aerobic reactor system.

Simultaneous toxicity and nutrient removals in simulated DEPHANOX (anaerobic/anoxic/oxic sequentials) process treating dinitrotoluene and trichlorotoluene.

A modified DEPHANOX process including two upflow sludge blanket reactors (USB) (anaerobic-upflow sludge blanket -UASB and anoxic-upflow anoxic sludge blanket -UA(N)SB) and one completely stirred tank reactor (CSTR) system was simulated in order to detect the simultaneous removal of dinitrotoulene (DNT), trichlorotoluene (TCT), and nutrients. The phosphorus uptake and nitrification was excessively determined in aerobic CSTR reactor. Influent DNT was transformed to toluene, NH4-N and total aromatic amines (TAA) while TCT was transformed to toluene and dichlorotoluene (DCT) under anaerobic and anoxic conditions. Increasing the volumetric loading rate of DNT and TCT from 18 mg/L x day and 0.35 g/L x day to 60 mg/L x day and 1.2 g/L x day, respectively, resulted in higher COD conversion (70-80%) rates and methane productions (250-300 ml/day) in anaerobic reactor. 90% NO3-N and 87% PO4-P were achieved in anoxic and aerobic reactors at DNT and TCT loading rates as high as 40-60 mg/L x day and 0.8-1.2 g/L x day, respectively. The TAA produced under anaerobic and anoxic conditions were ultimately removed under the aerobic stage. The UASB and anoxic UASB reactor effluents were less toxic relative to the influent when analyzed by anaerobic toxicity tests and specific methanogenic activity tests, indicating that such anaerobic/anoxic aerobic sequential treatments could be able to reduce toxic organics together with nutrient removal.

Ultimate azo dye degradation in anaerobic/aerobic sequential processes.

The treatability of Remazol Black-5 was studied in an anaerobic/aerobic sequential process. Laboratory scale UASB/CSTR reactors were used and operated at different organic loadings and HRTs to investigate the COD, color removal, and methane gas production efficiencies. The effect of both sludge age and HRT on the color and COD removal efficiencies were also investigated. The reactive dye used in this study contains the groups N=N, -SO3, S=O and is in use in some of the textile industries in Turkey. The studies were carried out in continuous mode and the effluent of the UASB reactor was used as feed in the CSTR reactor. COD removal efficiencies decreased from 56 to 27% with increases in COD loadings from 5 kg COD/m3.day and 25 kg COD/m3.day in the anaerobic UASB reactor. The color removals were 92 and 87%, respectively, for the aforementioned organic loadings. The methane percentages were found to be 50 and 76% at organic loading rates of 2.49 kg COD/m3.day and 14.8 kg COD/m3.day, respectively. 28, 42, and 90% COD removal efficiencies were obtained at sludge retention times of 1.7, 5.7 and 11 days in the aerobic CSTR reactor. Optimum sludge age was 11 days in aerobic reactor and 67 and 28% COD removal efficiencies were obtained at F/M ratios of 0.05-0.17 and 0.30-1.4 kg COD/kg MLSS.day. 90-95% color and 40-60% COD removal efficiencies were obtained depending on the applied organic loadings in the UASB reactor. The remaining COD was removed with a treatment efficiency of 85-90% in the aerobic CSTR reactor.

Incorporation of toxicity tests into the Turkish industrial discharge monitoring systems.

A toxicity evaluation is an important parameter in wastewater quality and in the monitoring of discharged effluents. Some organic and inorganic compounds at toxic levels have been detected in industrial discharges, resulting in plant upsets and discharge permit violations. In some cases, even though the effluent does not exceed the chemical-specific discharge limits, the results of toxicity tests show potential toxicity. Knowledge of the toxicity of effluents can benefit treatment plant operators in optimizing plant operation, protecting receiving water quality, and establishing sewer discharge permits. In the Turkish regulations only toxicity dilution factor with fish is part of the toxicity monitoring program of permissible wastewater discharge. This study investigated the acute toxicity of pulp-paper, leather, and petrochemical industry wastewaters by traditional and enrichment toxicity tests and emphasized the importance of toxicity tests in wastewater discharge regulations. The enrichment toxicity tests are novel applications indicating whether there is potential toxicity or stimulation conditions. Different organisms were used, including bacteria (Floc and Coliform bacteria) algae (Chlorella sp.), fish (Lepistes sp.), and protozoan species (Vorticella sp.) to represent four trophic levels. The toxicity test results were compared with chemical analyses to identify the pollutants responsible for the toxicity in the effluent wastewater samples. Toxicity of the effluents could not be explained by using physicochemical analyses in five cases for the leather and four cases for the pulp-paper and petrochemical industries. The results clearly showed that the use of bioassay tests produce additional information about the toxicity potential of industrial discharges and effluents.