Biological treatability of m-aminophenol plant wastewater containing structural isomers of benzene with different substituents

Bench scale studies on treatability of combined wastewater from an m-aminophenol (m-AP) manufacturing plant using acclimated activated sludge and an organic loading of 0.12 kg BOD kg MLVSS⁻¹ day⁻¹ resulted in removal of around 96% BOD and 59% TOC. Analysis of raw and treated wastewaters by HPLC revealed that resorcinol and m-AP present in the wastewater were completely removed, while m-nitrobenzene sulphonate (m-NBS) removal was only partial. However, in a batch system, preferential utilization of m-NBS was observed when a mixture of m-NBS and resorcinol was fed to m-NBS acclimated activated sludge. Electrolytic respirometric studies showed that oxygen uptake rate of m-NBS acclimated activated sludge with m-NBS as the substrate was not affected in the presence of resorcinol. Also m-AP and metanilic acid (m-AA) had no effect on either resorcinol or m-NBS removal by respective acclimated activated sludges. The incomplete removal of m-NBS from combined wastewater may probably be attributed to the metabolic interaction between m-NBS and an unidentified compound which appeared in the HPLC chromatograms of the raw and treated wastewaters.     

Removal of nitrogen, phosphorus and COD from waste water using sand filtration system with Phragmites Australis

The removal efficiencies of nitrogen, phosphorus and COD from waste water were examined using sand filtration systems with Phragmites australis (Cav.) Trin. ex. Steudel. The quality of effluent waters from the system with plant were far better than those from the one without plant, implying Phragmites could incorporate nitrogen and phosphorus into its tissues and promote phosphorus absorption onto the sand by the release of oxygen from the roots. The P-pot provided with the influent containing 198 mg l^- of total nitrogen and 21 mg l^-1 of total phosphorus had the highest biomass of Phragmites. Harvestable above-ground biomass accounted for about 3.5 kg m^-2 and removable nitrogen and phosphorus accounted for 69 and 6 g m^-2 respectively.The removal rates of total nitrogen and phosphorus in the system with Phragmites receiving variable amounts of COD were almost at the same level and also much better than those of the systems without plant, implying that the different COD concentrations in the influent media do not impair the removal efficiencies of nitrogen and phosphorus. Also Phragmites was found to resist COD concentration as high as 128 mg l^-1, and signs of clogging were not detected in this system throughout the experiment.     

High nitrate denitrification in continuous flow-stirred reactors

Continuous flow stirred reactors were used to evaluate the maximum denitrification specific removal rates for influent solutions made from NH₄NO₃, CaNO₃, KNO₃ and UO₂ fuel fabrication waste water. Nitrate substrate concentrations ranged from 0.01 to 20 kg NO₃/m³. Values for U_max (maximum specific substrate removal rate per unit mass of microorganisms per unit time, days⁻¹) were determined using graphical solutions to the Lineweaver-Burk equations. For NH₄NO₃ solutions at nitrate substrate concentrations <6 kg NO₃/m³ the value for U_max was found to be 1.73 days⁻¹. At nitrate substrate concentrations >6 kg NO₃/m³ a nonlinear relationship was observed in the Lineweaver-Burk plots indicating nitrate substrate inhibition. Specific removal rates at nitrate concentrations >6 kg NO₃/m³ averaged <1.0 days⁻¹. Ammonia toxicity may also have occurred as the pH of the mixed liquor was near 8. Methanol concentrations as high as 11.6 kg CH₃OH/m³ did not inhibit denitrification rates. The highest specific removal rates recorded (3.13 ± 0.56 days⁻¹) were with influents made from UO₂ fuel fabrication waste water.     

Non‐steroidal anti‐inflammatory pharmaceutical wastewater treatment using a two‐chambered microbial fuel cell

The two‐chambered microbial fuel cell (MFC) was designed and used for studying the efficiency of the real wastewater treatment from a non‐steroidal anti‐inflammatory pharmaceutical plant as well as from synthetic wastewater containing diclofenac sodium (DS). The removal of the contaminants was expressed regarding chemical oxygen demand (COD) removal, as measured by spectrophotometry experiments. Moreover, the effect of two different types of the cathode on current characteristics and COD removal was investigated. This research showed that the Pt‐coated Ti cathode could lead to higher efficiency of both power density and COD removal. In this case, the results indicated that the maximum power density (P_max) was 20.5 and 6.5 W/m³ and the maximum COD removal was 93 and 78% for MFCs using real and synthetic wastewater, respectively.     

Removal of asbestos fibres from potable water by coagulation and filtration

There is growing concern that asbestos-like fibres in drinking water could be a potential health hazard. Methods are described for removing asbestiform fibres from potable water based on modifications to conventional water treatment techniques. These include simple sand filtration, diatomaceous earth filtration, chemical coagulation or combinations of these depending on the degree of removal required. The most effective method, involving chemical coagulation with iron salts and polyelectrolytes followed by filtration, resulted in better than 99·8% fibre removal from water containing 12 x 10⁶ fibres 1⁻¹.     

Removal of arsenic from water: Effect of calcium ions on As(III) removal in the KMnO4–Fe(II) process

A novel KMnO₄–Fe(II) process was developed in this study for As(III) removal. The optimum As(III) removal was achieved at a permanganate dosage of 18.6 μM. At the optimum dosage of permanganate, the KMnO₄–Fe(II) process was much more efficient than the KMnO₄–Fe(III) process for As(III) removal by 15–38% at pH 5–9. The great difference in As(III) removal in these two processes was not ascribed to the uptake of arsenic by the MnO₂ formed in situ but to the different properties of conventional Fe(III) and the Fe(III) formed in situ. It was found that the presence of Ca²⁺ had limited effects on As(III) removal under acidic conditions but resulted in a significant increase in As(III) removal under neutral and alkaline conditions in the KMnO₄–Fe(II) process. Moreover, the effects of Ca²⁺ on As(III) removal in the KMnO₄–Fe(II) process were greater at lower permanganate dosage when Fe(II) was not completely oxidized by permanganate. This study revealed that the improvement of As(III) removal at pH 7–9 in the KMnO₄–Fe(II) process by Ca²⁺ was associated with three reasons: (1) the specific adsorption of Ca²⁺ increased the surface charge; (2) the formation of amorphous calcium carbonate and calcite precipitate that could co-precipitate arsenate; (3) the introduction of calcium resulted in more precipitated ferrous hydroxide or ferric hydroxide. On the other hand, the enhancement of arsenic removal by Ca²⁺ under acidic conditions was ascribed to the increase of Fe retained in the precipitate. FTIR tests demonstrated that As(III) was removed as arsenate by forming monodentate complex with Fe(III) formed in situ in the KMnO₄–Fe(II) process when KMnO₄ was applied at 18.6 μM. The strength of the “non-surface complexed” As–O bonds of the precipitated arsenate species was enhanced by the presence of Ca²⁺ and the complexation reactions of arsenate with Fe(III) formed in situ in the presence or absence of Ca²⁺ were proposed.     

Removal of metribuzin by sulfate radical‐based photooxidation: multi‐objective optimization by central composite design

The objective of this study was to optimize the experimental conditions for maximum removal efficiency and minimum operating cost for removal of metribuzin pesticide from aqueous solution. Central Composite Design model was applied as Response Surface Design. In the model, independent parameters were ultraviolet irradiation time, persulfate anion dosage, TiO₂ dosage, pH and response parameters were metribuzin removal (%) and operation cost. Analysis of variance (ANOVA) was used to describe the significance level of factors on the multiple performance characteristics considered. It has been found that the most suitable model is the quadratic model to explain the both responses and the correlation coefficient (R²) of the relationship between the actual metribuzin removal and the predicted removal was calculated as 0.9518. As a result of multi‐optimization, removal efficiency of 84.59 (%) and operation cost of 4.44 (€/g) were obtained at ultraviolet irradiation time at 12.03 min, persulfate anion concentration at 4.909 g/L, TiO₂ concentration at 0.197 g/L and pH at 4.     

Algae removal by fine sand/silt filtration

A laboratory scale study was undertaken to determine the potential of a method of filtering algae from water using fine sand/silt as the filter media. Five median sand sizes (0.064–0.335 mm) and four bed depths (3.175–12.700 mm) were examined in constant head experiments with the algae Scenedesmus quadricauda. A total of 46 experiments were conducted with continuous measurements of filtration rate, head loss and effluent quality. All media with median sand sizes at or below 0.200 mm gave consistently high algae removal rates. The average removal was 97.27% (based on fluorescence) with a low average initial head loss across the filter media of 7.3 cm (median grain size diameter of 0.200 mm with the bed depth of 3.175 mm). Initial filtration rates obtained in the experimental apparatus were as high as 226 m³ m⁻²–day⁻¹ (3.84 gpm ft⁻²), comparable to conventional sand units. Run times were short due to surface clogging of the media. No chemical addition was required to obtain high removal levels.     

Palm oil refinery wastes treatment

Effluent from the refining of crude palm oil was subjected to physical-chemical and biological treatment. An inclined corrugated parallel plates oil separator spaced at 25 mm was used with hydraulic loading rates of 0.2, 0.5 and 1 m³ m⁻²-h. 91% oil and grease removal could be achieved at 0.2 m³ m⁻²-h. Coagulation and flocculation carried out on batch samples after oil and grease separation revealed that with 100 mg l⁻¹ alum addition BOD was reduced from 3500 to 450 mg l⁻¹ and COD from 8600 to 750 mg l⁻¹ after 30 min settling. Higher doses of alum and doses of polyelectrolyte, activated carbon and sodium hypochloride did not yield significant additional reductions in BOD and COD. Batch dissolved air flotation (DAF) removed 90% of the suspended solids with 2.7% solids in the thickened sludge at an A/S ratio of 0.014. This method yielded the similar effluent quality as the inclined corrugated plates oil and grease separator. Field data from a DAF plant compare closely with data achieved in this study. Activated sludge treatment on the effluent from the oil separator yielded a BOD of 46 mg l⁻¹ with a loading rate of 0.3 g BOD (g MLVSS)⁻¹-day. Total dissolved solids (TDS) remained high and removal through coagulation and chemical oxidation brought the COD level down to around 180 mg l⁻¹. Biokinetic coefficients Y, k_dK and K₃ were found to be 0.85 g VSS (g BOD)⁻¹, 0.016 day⁻¹, 0.12 g BOD (g VSS)⁻¹-day and 510 mg l⁻¹ BOD respectively.     

The response of activated sludge to a polychlorinated biphenyl (KC-500)

A kind of polychlorinated biphenyl, Kanechlor 500, was selected as a representative industrial toxicant, and its effects on biochemical characteristics of the activated sludge and its behavior in the biological treatment process were observed at concentrations of 0, 1.5 and 10 μg l⁻¹.The presence of PCB in synthetic sewage resulted in changes in the microflora and aldolase activity of the activated sludge even at low concentration of PCB such as to be 1 μg l⁻¹, and it was also demonstrated that dosing PCB caused remarkable increase of the oxygen uptake activity. Furthermore, PCB was not found to undergo degradation to any appreciable extent during the aeration process nor as the result of anaerobic digestion, although low concentrations did not exert an influence on COD and BOD removal efficiency in the process. In synthetic sewage PCB was shown to undergo mobilization from the aqueous phase to the activated sludge as evidenced by a concentration factor on the order of 10³–10⁴.     

Ammonia removal from aqueous solution by membrane distillation

Environmental regulation, increased pressure on water resources and rising cost for wastewater discharges make wastewater treatment for recycling an essential investment for many industries. Ammonia is a major pollutant in many industrial and agricultural wastewaters, and its elimination is essential for wastewater to be reused or meeting local discharge standards. In this study, the removal of ammonia from dilute aqueous solution has been investigated using sweep gas and vacuum membrane distillation (SGMD and VMD). Factors that affect the separation process such as feed and air flow rates, vacuum degree and feed temperature have been investigated. Overall, mass transfer coefficients (K_ov) were calculated, and the results indicated that K_ov for VMD is higher than that for SGMD under similar operation. Overall, ammonia mass transfer coefficient up to 12.06 × 10^?5 and 5.63 × 10^?5 m/s can be achieved for VMD and SGMD, respectively. The ammonia removal efficiency was enhanced by increasing sweep gas flow rate or by decreasing downstream pressure.     

Continuous cultivation of Debaryomyces hansenii (LAF-3 10 U) on dodecane in synthetic desalter effluent at varying dilution rates on dodecane

Desalter effluent (DE) is typically discharged into a petroleum wastewater treatment plant, but its high salt concentration deteriorates the biological treatment. This study used various dilution rates to investigate the treatment of a synthetic DE containing dodecane under saline conditions using a halotolerant yeast, Debaryomyces hansenii, to determine the optimum substrate concentration for use in continuous stirred-tank reactors (CSTRs). A literature review indicated that this study was the first to examine the biological treatment of DE using D. hansenii in a CSTR system. At a low dodecane substrate concentration, DE did not inhibit D. hansenii growth, and the experimental data approached the Monod model, with μ_max and K_s selected as 0.08 h⁻¹ and 1575 mg L⁻¹, respectively. The optimum removal of chemical oxygen demand (95.7% and 85%) was obtained at dilution rates of 0.007 and 0.026 d⁻¹. Using D. hansenii in a CSTR system appeared to be a sustainable approach for the biological treatment of DE. Scale-up of these laboratory findings to the industrial scale is required to confirm that petroleum DE can be treated using equalization and filtration tanks as a continuous bioreactor. Adjusting the dilution rate can provide sufficient time for biodegradation and hydrocarbon removal from high salt DE by halotolerant yeasts like D. hansenii.     

Role of aquatic plants in wastewater treatment by artificial wetlands

This report describes investigations using artificial wetlands which quantitatively assess the role of each of three higher aquatic plant types, Scirpus validus (bulrush), Phragmites communis (common reed) and Typha latifola (cattail), in the removal of nitrogen (via sequential nitrification-denitrification), BOD and TSS from primary municipal wastewaters. During the period August 1983–December 1984, the mean ammonia concentration of 24.7 mg l⁻¹ in the primary wastewater inflow (hydraulic application rate = 4.7 cm day⁻¹) was reduced to mean effluent levels of 1.4 mg l⁻¹ for the bulrush bed, 5.3 mg l⁻¹ for the reed bed and 17.7 mg l⁻¹ for the cattail bed, as compared to a mean value of 22.1 mg l⁻¹ for the unvegetated (control) bed. For all three vegetated beds, the mean effluent ammonia values were significantly below that for the unvegetated bed and for the inflow. The bulrushes and reeds (in that order) proved to be superior at removing ammonia, both with mean effluent levels significantly below that for the cattail bed. The high ammonia-N (and total N) removal efficiencies shown by the bulrush and reed beds are attributed to the ability of these plants to translocate O₂ from the shoots to the roots. The oxidized rhizosphere so formed stimulates sequential nitrification-denitrification. Similarly BOD removal efficiencies were highest in the bulrush and reed beds, both with mean effluent BOD levels (5.3 and 22.2 mg l⁻¹, respectively) significantly below that for the unvegetated bed (36.4 mg l⁻¹) and equal to or better than secondary treatment quality (30 mg l⁻¹). Our results demonstrate that higher aquatic plants can indeed play a significant role in secondary and advanced (N removal) wastewater treatment by wetland systems, a role that is completely distinct from that associated with their pollutant uptake capacity.     

Surface mass transfer processes during colour removal from effluent using silica

The effects of several variables on the initial rate of Astrazone Blue (Basic) dye removal have been investigated. The surface mass transfer coefficients have been determined and correlated as the dimensionless mass transfer term Sh/Sc^0.33, as a function of agitation, initial dye concentration, silica particle size and temperature.     

Biodegradation of monoaromatic hydrocarbons in aquifer columns amended with hydrogen peroxide and nitrate

The ability of indigenous microorganisms to degrade benzene, toluene, ethylbenzene and xylenes (BTEX) in laboratory scale flow-through aquifer columns was tested separately with hydrogen peroxide (110 mg/l) and nitrate (330 mg/l as NO₃⁻) amendments to air-saturated influent nutrient solution. The continuous removal of individual components from all columns relative to the sterile controls provided evidence for biodegradation. In the presence of hydrogen peroxide, the indigeneous microorganisms degraded benzene and toluene (> 95%), meta- plus para-xylene (80%) and ortho-xylene (70%). Nitrate addition resulted in 90% removal of toluene and 25% removal of ortho-xylene. However, benzene, ethylbenzene, meta- and para-xylene concentrations were not significantly reduced after 42 days of operation. Following this experiment, low dissolved oxygen (< 1 mg/l) conditions were initiated with the nitrate-amended column influent in order to mimic contaminated groundwater conditions distal from a nutrient injection well. Toluene continued to be effectively degraded (> 90%), and more than 25% of the benzene, 40% of the ethylbenzene, 50% of the meta- plus para-xylenes and 60% of the ortho-xylene were removed after several months of operation.     

Removal of leachate pollutants using flocculation method at simultaneous factors of optimum pH and Tacca leontopetaloides biopolymer flocculant (TBPF) dosage via face-centred central composite design

The effect of the interaction factor between pH and dosage is important in leachate wastewater treatment. This study aims to remove leachate pollutants such as turbidity, total suspended solid (TSS), chemical oxygen demand (COD) and colour using simultaneous factors of plant-based Tacca leontopetaloides biopolymer flocculant (TBPF) dosage and leachate pH. The flocculation process was carried out through jar test by applying the perikinetic theory and statical analysis (face-centred central composite design). The results found that the optimum leachate pH and TBPF dosage were pH 3 and 150 mg/L, respectively. The highest removal of leachate pollutants reached up to 69% with a second-order perikinetic model; R² = 0.9545 and k = 9 × 10⁻⁶ L/mg/min were obtained. Simultaneous interaction factors between leachate pH and TBPF dosage on turbidity and TSS removal were found significant and hence can be applied in the actual leachate wastewater treatment industry, particularly at the primary stage using the proposed model.     

Removal of nitrogen from industrial wastewaters with the use of algal rotating disks and denitrification packed bed reactor

An attempt was made to use an algal rotating disk system in a two-step biological purification of nitrogen fertilizer industry wastewaters. The proposed method involved the removal of ammonium by Stichococcus bacillaris growing on the rotating disk and of oxidized forms of nitrogen by denitrifying bacteria. The use of a rotating algal disk followed by denitrification bed as the second step of biological treatment removed about 90% of nitrogen from the wastewater. A change of purification sequence resulted in the appearance of NO ⁻₃ and NO⁻₂ in the purified wastewater caused by the activity of nitrifying bacteria accompanying algae in the biological film on the disk. It was found that methanol used as a carbon source for denitrifying bacteria could be replaced by organic matter of algal origin.     

The removal of chromium(VI) from dilute aqueous solution by activated carbon

The removal of chromium(VI) by activated carbon, filtrasorb 400, is brought by two major interfacial reactions: adsorption and reduction. Chemical factors such as pH and total Cr(VI) that affect the magnitude of Cr(VI) adsorption were investigated. The adsorption of Cr(VI) exhibits a peak value at pH 5–6. The particle size of carbon and the presence of cyanide species do not change the magnitude of chromium removal. The reduced Cr(VI), e.g. Cr(III) is less adsorbable than Cr(VI).The free energy of specific chemical interaction, ΔG^chem was computed by the Gouy-Chapman-Stern-Grahame model. The average values of ΔG^chem are −5.57 RT and −5.81RT, respectively, for Cr(VI) and CN. These values are significant enough to influence the overall magnitude of Cr(VI) and CN adsorption. Results also indicate that HCrO⁻₄ and Cr₂O²⁻₇ are the major Cr(VI) species involved in surface association.     

Treatment of chromium‐bearing wastewaters with constructed wetlands

Chromium can have detrimental effects on most organisms, including humans. The present study focused on the effect of treating chromium‐bearing, organic‐rich wastewater on constructed wetland performance. Eight laboratory‐scale systems were used to study organic matter and chromium removals, with three features tested in duplicate: media with proven chromium sorption capacity, vegetation presence and intermittent influent loading. A set of two wetlands acted as the base design. Average BOD₅ and chromium removal rates were 13.4 g/m² day and 135 mg Cr/m² day, respectively. From an influent chromium concentration of 5 mg/L, <0.5 mg/L could be detected at the outlet during the study in all systems. Chromium removal efficiencies were statistically different for all systems (P<0.01), except when comparing the base design against the intermittent feed systems (P>0.05). Overall treatment performance of all systems was remarkably good in spite of significant chromium content and salinity.     

A comprehensive study on the biological treatabilities of phenol and methanol—I. Analysis of bacterial growth and substrate removal kinetics by a statistical method

An unbiassed statistical method was developed to evaluate kinetic parameters in the biological oxidation of wastewaters. Through the statistical analyses of the biological oxidation kinetics, it was shown that the kinetic equations satisfactorily described the bacterial growth and substrate removal kinetics where X is biomass concentration, S is substrate concentration, t is time, a is cell yield coefficient, k_d is cell decay coefficient, K_s is Michaelis-Menten constant, and k is substrate removal rate coefficient. The coefficients K_s and a changed with temperature insignificantly while k and k_d were closely related to it. The temperature independent coefficients K_s and a were estimated to be 236 mg 1⁻¹ (standard deviation, σ = 70 mg 1⁻¹) and 1.21 (σ = 0.06) respectively for phenol, and 2330 mg 1⁻¹ (σ = 1410 mg 1⁻¹) and 1.25 (σ = 0.45) respectively for methanol based on total organic carbon (TOC) and volatile suspended solids (VSS). The oxygen utilization rate can be formulated as where Rr is the oxygen utilization rate (mg 1⁻¹ O₂ time⁻¹), as′ is a coefficient designating oxygen requirement per substrate utilized, and b′ is a coefficient designating oxygen requirement per biomass for endogeneous respiration. The coefficient a′ was 1.39 for phenol and 2.23 for methanol, and b′ was 1.42 k_d for both substances based on TOC and VSS.