Biological lagooning of phenols-containing oil shale ash heaps leachate

In the course of the present study the biological treatment of leachate from oil shale semicoke ash heaps in a wastewater lagoon was investigated. The lagooning process was simulated by laboratory-scale batch processes and a lagoon, by applying different aeration conditions at 20°C.

Treatment in the lagoon significantly reduced chemical oxygen demand (COD), biochemical oxygen demand (BOD) and phenols in the leachate. A removal of 55–64% of COD was achieved. The removal of phenols, estimated on the basis of identified phenolic compounds, was 80–88%. The best removal of COD, up to 70%, was achieved in the intermittently aerated batch, while in the non-aerated batch the removal was 41%. In the intermittently aerated batch the removals of phenol, methylphenols and dimethylphenols were on the average from 95 to over 99%. All the tested systems showed lower removals of resorcinols compared to those of monohydric phenols.

This study indicates that leachate from oil shale semicoke ash heaps could be treated in an aerated lagooning system, and that the biological treatment of the high pH leachate is feasible without pH adjustment.     

Combined γ-ray irradiation-activated sludge treatment of humic acid solution from landfill leachate

Humic acid, which is a typical microbially refractory organic substance, was extracted from a landfill leachate. The humic acid solution (COD = 367 mg 1⁻¹; TOC = 293 mg 1⁻¹; BOD = 27 mg 1⁻¹) was applied to a batch scale activated sludge treatment after the modification of its biodegradability by γ-ray irradiation. The BOD increased to 64 mg 1⁻¹ by irradiation of 15 kGy (1.5 Mrad), while the COD and TOC decreased to 231 and 230 mg 1⁻¹, respectively. When the irradiated sample was treated with an activated sludge, the BOD decreased rapidly in 2–3 h to about 15 mg 1⁻¹ which was a similar value as the unirradiated sample was treated. The elimination efficiency of TOC by the sludge treatment was approximately equal to that obtained by irradiation of 15 kGy. These facts suggest a utility of applying microbial processes after radiation treatment of microbially refractory wastewaters.     

Stabilized leachates: ozone-activated carbon treatment and kinetics

Ozone has been used as a pre-oxidation step for the treatment of stabilized leachates. Given the refractory nature of this type of effluents, the conversion of some wastewater quality parameters has been moderate after 1 h of ozonation (i.e. 30% chemical oxygen demand (COD) depletion). Ozone uptake was calculated in the interval 1.3–1.5 g of ozone per gram of COD degraded. An optimum dose of ozone has been experienced in terms of biodegradability of the processed effluent (60 min of treatment, 1×10⁻³ molL⁻¹ ozone inlet feeding concentration and 50 Lh⁻¹ gas flow-rate). pH and other typical hydroxyl radical generator systems exerted no influence on the efficiency of the process, suggesting the negligible role played by the indirect route of oxidation (generation of hydroxyl radicals). The ozonated effluent was thereafter treated in a second adsorption stage by using a commercial activated carbon. Removal levels up to 90% of COD in approximately 120 h were experienced for adsorbent dosages of 30 gL⁻¹. Both steps, the single ozonation and the adsorption stage have been modelled by using different pseudoempirical models.     

Aerobic treatment of piggery waste

The operating characteristics of laboratory waste treatment systems were studied during the aerobic degradation of pig excrement at different loading rates and temperatures. The treatment systems were of two types: one was operated with floc formation and gravity separation of liquid and suspended solid effluents; and a second was operated without floc formation or separation of the effluent into liquid and solid fractions.

With an operating temperature of 15°C the parameters most affected by loading rate were (1) the concentrations of suspended solids and chemical oxygen demand in the liquid effluent; (2) the pH value of the mixed liquor; (3) nitrification; (4) the BOD of the supernatant from the mixed liquor; and (5) output of suspended solids as a percentage of input.

The concentrations of suspended solids and chemical oxygen demand in the liquid effluents were little affected by loading rates in the range 0·05-0·15 g SS g MLSS⁻¹ d⁻¹ (0·02-0·06 g BOD g MLSS⁻¹ d⁻¹) but increased with increasing loading rate in the range 0·15-0·30 (0·06-0·12 BOD). At loading rates below about 0·17 g SS g MLSS⁻¹ d⁻¹ (0·07 g BOD g MLSS⁻¹ d⁻¹) the mixed liquors were acidic, with pH values down to 5·2, whereas at loading rates above about 0·80 (0·32 BOD) they were alkaline, with pH values up to 8·9. At intermediate loading rates the mixed liquor pH value was more variable though in general the higher the loading rate the higher also the pH value of the mixed liquor. Acidic conditions in the mixed liquors were attributed to the occurrence of nitrification, while in the absence of nitrification the mixed liquors remained alkaline. The concentration of BOD₅ in the supernatant from the mixed liquors increased with increasing loading rate from about 35 mg 1⁻¹ at a loading rate of 0·17 g SS g MLSS⁻¹ d⁻¹ (0·07 g BOD g MLSS⁻¹ d⁻¹) to about 250 mg 1⁻¹ at a loading rate of 1·30 (0·52 BOD). The output of suspended solids from the treatment systems represented about 70 per cent of input suspended solids at loading rates of about 0·15 g SS g MLSS⁻¹ d⁻¹ (0·06 g BOD g MLSS⁻¹ d⁻¹) and increased to about 100 per cent at loading rates of 0·80 (0·32 BOD). Output of chemical oxygen demand was about 60 per cent of input at the lower loading rates and 80–90 per cent at the higher ones.

Operation of treatment units at temperatures of 5 and 10°C instead of 15°C had little effect on the efficiency of degradation at loading rates in the range 0·085-0·20 g SS g MLSS⁻¹ d⁻¹ (0·034-0·08 g BOD g MLSS⁻¹ d⁻¹), but nitrification was prevented at 5°C. At loading rates of 0·77 (0·31 BOD) and 1·46 (0·58 BOD) operation at 25°C appeared to increase the amount of degradation as compared with that achieved at 15°C.

The practical implications of the results and possible future approaches to the aerobic treatment of farm wastes are discussed.     

An appraisal of the effect of biological treatment on the environmental quality of high-yield mechanical pulping effluents

Before biological treatment, the effluents from one CTMP (chemi-thermomechanical pulping) and three TMP (thermomechanical pulping) mills were acutely lethal to fathead minnows (Pimephales promelas) and the water flea Ceriodaphnia with 48-h LC₅₀ values of 2.2 to > 50%. The effluents also caused chronic effects at concentrations of 0.01–5.3%. After biological treatment, effluents from the three TMP mills were not acutely lethal to either test species. Biotreated effluents from the CTMP mill were also not acutely lethal to minnows but were lethal to Ceriodaphnia (48-h LC₅₀: 54–80%). The chronic effects of biotreated effluents occurred at concentrations of 47 to > 100% for fathead minnows and at 5–37% for Ceriodaphnia. Biological treatment also reduced the levels of BOD (>80%), COD (>60%) and wood extractives (>99%).     

Combined biological and ozone treatment of log yard run-off

Batch biological treatment of log yard run-off reduced biochemical oxygen demand (BOD), chemical oxygen demand (COD) and tannin and lignin (TL) concentration by 99%, 80%, and 90%, respectively. Acute (Microtox) toxicity was decreased over treatment, from an initial EC50 of 1.83% to a value of 50.4% after 48 h of treatment. Kinetics of biodegradation were determined using respirometry and fitted using the Monod and Tessier model. For the Monod model the maximum substrate uptake rate, and Ks values determined were 0.0038 mg BOD/mgVSS min, and 1.4 mg/L, respectively. The efficacy of ozone as a pre- and post- biological treatment stage was also assessed. During ozone pretreatment, TL concentration and acute toxicity were rapidly reduced by 70% and 71%, respectively. Pre-ozonation reduced BOD and COD concentration by < 10%, however a larger fraction of residual COD was non biodegradable after ozonation. Biologically treated effluent was subjected to ozonation to determine whether further improvements in effluent quality could be achieved. A reduction in COD and TL concentration was observed during ozonation, however no further improvement in toxicity was observed. Ozonation increased BOD by 38%, due to conversion of COD to BOD.     

Pre-acidification in anaerobic sludge bed process treating brewery wastewater

The effect of pre-acidification on anaerobic granule bed processes treating brewery wastewater was the focus of a comparison study employing two configurations, (a) a single stage upflow anaerobic sludge bed (UASB) and (b) an upflow acidification reactor in series with a methanogenic UASB. The pre-acidification reactor achieved 20±4% SCOD removal and 0.08±0.003 L of methane produced per gram of SCOD removal at a hydraulic retention time (HRT) of 0.75–4 h. Butyric acid was not detected and short chain fatty acids (SCFAs) were mainly acetic and propionic acids. The acidification ratio was about 0.42±0.02 g SCFAs as COD/g of influent COD.

Both systems’ critical loading rate to achieve 80% COD removal was established at 34–39 kg COD/m³ of total sludge bed volume per day. SCOD removal efficiency of 90±3% was achieved by both systems at an organic loading rate of 25±1 kg COD/m³ of total sludge bed volume per day, indicating that the installation of an acidification reactor had no effect in terms of the maximum granular activity, biomass granulation and the settleability of granules. At an organic loading rate of 67 kg COD/m³ of total sludge bed volume per day at an HRT of 1 h, the series system outperformed the single UASB by a removal of 62 compared to 57%.     

Involvement of protozoa in anaerobic wastewater treatment process

It is only very rarely recognised in literature that anaerobic reactors may contain protozoa in addition to various bacterial and archeal groups. The role of protozoa in anaerobic degradation was studied in anaerobic continuous stirred tank reactors (CSTR) and batch tests. Anaerobic protozoa, especially the ciliated protozoa, have direct influence on the performance of CSTR at all organic loading rates (1–2 g COD l⁻¹ d⁻¹) and retention times (5–10 days). The studies revealed that chemical oxygen demand (COD) removal is strongly correlated to ciliate density in CSTR fed with oleate (suspended COD) and acetate (soluble COD). There was no significant difference in COD removal between reactors fed suspended COD and those fed soluble COD. However, the diversity and number of ciliates is greater in CSTR fed with particulate feed. The mixed liquor suspended solids (MLSS) representing biomass was significantly lower (16–34%) in CSTR with protozoa. In batch tests, increased COD removal and methane production was observed in sludge having ciliates as compared with sludge without protozoa. Methane production increased linearly with number of ciliates (R²=0.96) in batch tests with protozoa. Direct utilization of COD by flagellates and ciliates was observed in bacteria-suppressed cultures. The technological importance of these results is that reactors with protozoa-rich sludge can enhance the rate of mineralization of complex wastewater, especially wastewater containing particulate COD.     

Lagooned, secondary effluents as water source for extended agricultural purposes

Chlorination of trickling filter effluents at 40 mg l⁻¹ chlorine for 4 h and 20 mg l⁻¹ for 4 and 6 h showed very limited coliform survival. The number of viruses decreased from a few hundred in 100 ml before chlorination to 0 after chlorination. A 70,000 m³ pond (4 m deep) was used for holding non-chlorinated secondary effluents for 73 days. Bacterial and viral counts were performed every few days. In addition BOD, TC, pH and solar radiation were monitored. After this, the water was pumped out and chlorinated in a pipeline with 8 or 20 mg l⁻¹ chlorine. After chlorination the coliform count was reduced by from 3 to 5 orders of magnitude. After storage for 43 days the non-chlorinated secondary effluents viral count was nil. After chlorination these effluents were also virus-free.

In the second experiment, secondary effluents chlorinated with 20 mg l⁻¹ chlorine with a contact period of 2 h. They were then introduced to the pond. No viruses were found in the incoming water, neither during holding nor after the second chlorination, Coliform regrowth was very slow because of the temperature of the water was only 18–20°C. Identification of the M. Endo membrane filter grown isolated colonies proved that E. coli I disappeared, and all the coliforms were of non-fecal origin or that other growths were non-coliform organisms growing on the MF.

The third experiment was a repetition of the first, in spring, after the temperatures rose. The results confirmed the findings in the first experiment. Therefore, it is thought that 70 days holding of wastewater would permit its extensive agricultural use. For safety, the addition of 20 mg l⁻¹ chlorine to effluents and a short storage could be adequate from a public health point of view.     

Electrochemical treatment of cigarette industry wastewater: feasibility study

The electrochemical treatability of wastewater from the cigarette industry has been investigated in this paper using cast iron electrode. The treatment efficiency was monitored in terms of COD, BOD and suspended solids concentration. The cast iron anode was found effective in treatment of the above-mentioned wastewater. About 56% of COD and 84% of BOD removal was observed at 3.5 A current for 5 h of electrolysis. The effect of increase in surface area of anode reduces electrolysis time and also energy consumption per kg of COD removal. The treated effluent was subjected to chemical coagulation studies using Ca(OH)2 as coagulant. The final treated effluent was found to confirm the stipulated standards for safe disposal into surface water bodies (Indian Standards). It was concluded that the electrochemical treatment followed by chemical coagulation could be opted as an alternate treatment scheme for the present industry.     

The treatment of leachates from domestic wastes in landfills—I: Aerobic biological treatment of a medium-strength leachate

A medium-strength leachate from domestic solid wastes in a landfill (COD 5000 mg l⁻¹, BOD 3000 mg l⁻¹ was treated using aerobic biological processes in continuous-flow, laboratory-scale reactors at low temperatures. Each unit was completely mixed, and mixed liquor was wasted such that solids retention time (SRT) was equal to the hydraulic retention period.At 10 C with addition of phosphate (COD:P less than 100:1) SRT values of 10 days were required to obtained well-clarified effluents, and high removal of BOD (>;98%) and COD (>;92%). Reduction of temperature to 5°C resulted in adverse effects on settling of sludges from units with SRT values of less than 10 days, but in other units good removal of organic materials could still be obtained. These units operated successfully with concentrations of mixed liquor volatile suspended solids (MLVSS) of 1450 mg l⁻¹, equivalent to a ratio of F/M of 0.21 kg BOD kg⁻¹ MLVSS day⁻¹ or less. Removal of ammoniacal nitrogen which took place (influent concentration 80 mg l⁻¹ as N) resulted from incorporation in biomass, and at SRT values of 10 days no nitrification took place at 5 or 10 C. Higher concentrations of ammonia in influent leachates resulted in ammonia in effluents when the ratio of BOD:N was less than about 100:3.6. Increasing the SRT of units to 20 days resulted in erratic conversion to nitrite, but reduced pH-values and possible simultaneous denitrification caused floating sludges and poorly-clarified effluents. Removal of ammonia is identified as a major problem when treating leachates, and further research is recommended.     

A coupled photocatalytic-biological process for degradation of 1-amino-8-naphthol-3, 6-disulfonic acid (H-acid)

 There has been growing emphasis on the development of coupled treatment systems (e.g., advanced oxidation–biological) for treating poorly biodegradable wastewater. An attempt has been made in the present study to couple photocatalytic (TiO₂/UV) pretreatment with conventional activated sludge process to achieve improvement in the biodegradation of H-acid. The combination of titanium dioxide and UV light has been known to generate strong oxidants that degrade several organic pollutants into carbon dioxide via the formation of some intermediates. The intermediates formed may undergo biodegradation readily. Accordingly, photodegradation experiments were carried out initially at an optimized TiO₂ dose and the minimum pretreatment time required for transforming H-acid was identified. For this purpose, UV–vis spectrophotometry and high-performance liquid chromatography (HPLC) were extensively used. Subsequently, it was attempted to biodegrade untreated and pretreated H-acid using activated sludge from the textile industry acclimatized to H-acid. It was found that photocatalytic pretreatment of H-acid for 30 min, during which period approximately 8–10% chemical oxygen demand (COD) removal occurred, can be coupled to second-stage biological treatment for achieving enhanced biodegradation of H-acid.     

Sorption of copper by olive mill residues

A study on olive mill residues (OMR) as copper adsorbing material is reported in this work. A rough characterization of this waste material has been performed, by microanalysis and SEM pictures. Sorption tests with suspended OMR evidenced copper removal from solution, of about 60% in the investigated experimental conditions. The COD release in solution was also monitored during biosorption. Considering that it was significant, OMR washings with water were performed before biosorption. In this case the COD release in solution was reduced to less than 600 mg/L after two washings, while the OMR metal sorption properties did not change. Regenerated residues by acid solutions gave a copper removal of about 40%, in the same experimental conditions of the first adsorption test: regeneration with EDTA at different concentrations suggested that it presents a damage of adsorption active sites. On the other hand, the use of HCl and CaCl₂ led to completely regenerate the biosorbent material. Tests were also performed with a column filled with 80 g of OMR and the breakpoint was demonstrated to take place after that about 1 L solution was treated in the investigated experimental conditions. Regeneration tests permitted to demonstrate that a concentration factor of about 2 can be obtained in no-optimized conditions, highlighting the possibility of using OMR for the treatment of metal bearing effluents. The main advantage of the process would be the ‘‘low cost’’ biosorbing material, considering that it represents a waste in the olive oil production.     

Treatment of raw domestic sewage in an UASB reactor

The treatment of raw domestic sewage at ambient temperatures in an upflow anaerobic sludge blanket (UASB) reactor with a volume of 120 l. and a height of 1.92 m was studied. The sewage had an average BOD₅ of 357 mg l⁻¹ and COD of 627 mg l⁻¹. Approximately 75% of the organic materials were in the suspended fraction. The sewage temperature ranged from 18 to 28°C during the experimental period. The reactor operated continuously for 9 months and assessed self-inoculation and raw domestic sewage purification. The unit was started without inoculum and ran during the entire experimental period with a hydraulic retention time of 4 h. During the experiment, a sludge bed build-up was observed. At the end of the experimental period, the predominance of spherical granular particles up to 6–8 mm in diameter was evident.

After a 4-month operation, it was observed that the inoculation/acclimatization steps had been concluded. Removal efficiencies of BOD₅ = 78%, COD = 74% and TSS = 72% were obtained. A typical gas production factor of 80 l kg⁻¹ COD added was observed and the CH₄ content of the biogas was 69%.     

Automated fluorometric method for determination of boron in waters, detergents and sewage effluents

An automated method for the determination of boron in natural waters, detergents and sewage effluents is described. The method is based on the reaction of 4'-chloro-2-hydroxy-4-methoxybenzophenone (CHMB) with boron to produce fluorescent species, in a 90% sulfuric acid medium. The method has been made specific to remove any interferences from all major and minor ions and other organic compounds normally present in water. The method is capable of measuring different chemical forms of boron such as boric acid, borax, sodium perborate and tetraphenyl boron. The method analyses 10 samples per hour, in the 5–100 μg 1⁻¹ boron range. The rate of sample analysis can be increased to 20 per hour at higher concentration ranges. The limit of detection is 1 μg 1⁻¹ boron.     

Water purification by fluidized bed technique

Composite samples of wastewater obtained from a Nigerian Institution were clarified with a 10% solution of commercial alum and then filtered through a sand bed. The optimum dosage for the clarification was 400 mg 1⁻¹. Considerable reductions in colour, turbidity, suspended solids (SS), biochemical oxygen demand (BOD), chemical oxygen demand (COD), detergents of alkyl benzene sulphonate (ABS) base and total coliform bacteria were achieved in the samples.The samples were further purified by adsorption of their impurities by powered activated carbon (PAC) in a fluidized bed. The purification was done by two modes: fluidization with no beads added and fluidization with beads added. With 200 mg 1⁻¹ PAC and fluidization for 10 min, 92.8% COD reduction was achieved with no beads added while 98.5% COD reduction was achieved with 4% (v/v) glass beads added. Fresh surface water samples obtained from a dam were filtered through sand bed and similarly treated with 200 mg 1⁻¹ PAC in the fluidized bed. The qualities of the final effluents obtained from the two types of samples were comparable with the WHO standards for purified water/wastewater meant for recycling purposes.     

Transformation of organic matter and bank filtration from a polluted stream

A case study of the examination of the changes of organic matter in a small, highly polluted stream and the adjacent alluvial aquifer is presented. The investigated stream was actually a collector of effluents from baker's yeast and pharmaceutical industries. The stream was characterized by a COD of several thousands of mg O₂ l⁻¹, most of which was biodegradable organic matter. Biodegradation processes took place in the surface water, with consequent oxygen depletion in the stream. The organic matter content of the river sediment was more than 10% of its dry weight. Bank filtration of organic substances was investigated in a number of observation wells at distances of 5–150 m from the river (under different hydrological conditions). The infiltration of organic matter from the polluted stream into the aquifer was found to be significant only at hydrological conditions where the water level exceeds the altitude of the stream bed. The organic matter present in groundwater samples was mainly a humic/fulvic type, and was not degraded during the 64 days of the laboratory biodegradation experiment.     

Coupling of sequencing batch reactor and mesh filtration: operational parameters and wastewater treatment performance

Wastewater treatment performance of the combined process of sequencing batch reactor (SBR) and mesh filtration bio-reactor was investigated with a synthetic wastewater. In this system, the filtration was performed only by the water level difference between the reactor and the effluent port, with the help of a sludge layer which accumulated on the mesh filter.

A half volume of the mixed liquor was filtrated for ca. 1 h, and the filtration time was not affected by the initial pressure within the range of 0.5–2.0 m-H₂O. Since the mesh filter could effectively reject the biomasses in the reactor, the effluents contained SS of less than 1 mg/L and BOD of less than 10 mg/L under continuous or intermittent aeration conditions. Nitrogen was also removed effectively with the adjustment of aeration time under the intermittent aeration conditions.

The results obtained in this work indicate that mesh filtration could be effectively combined with SBR and improve the performance of SBR.

In addition, it was shown that the performance of the mesh filtration such as filtration time and solids separation was influenced significantly by the saccharide content in the exocellular polymer of the activated sludge.     

Optimization of electro-oxidation and electro-Fenton techniques for the treatment of oilfield produced water

Electrochemical advanced oxidation processes are the most promising methods for destroying and degrading organic and inorganic pollutants present in produced water effluents. This study presents the electro-oxidation process using graphite electrodes and electro-Fenton process using iron electrodes for the treatment of real produced water. The effect of operating parameters such as current density on chemical oxygen demand (COD) removal efficiency was addressed. The result showed that electro-Fenton process was more efficient than electro-oxidation process where it gave 98% as maximum COD removal efficiency with energy consumption of 1.9 kWh/dm³ at H₂O₂ concentration of 12 mM, current density of 10 mA/cm², temperature of 25°C, pH of 3, and treatment time of 80 min compared with 96.9% as maximum COD removal efficiency with energy consumption of 3 kWh/dm³ at pH of 6, current density of 10 mA/cm², temperature of 40°C, and reaction time of 80 min when using electro-oxidation process. These results demonstrated that electrochemical technologies are very promising methods for the treatment of produced water from oil/gas industry, so it can be safely disposed of or effectively reused for injection and irrigation.     

Influence of hydraulic shock loads and TDS on the performance of large-scale CETPs treating textile effluents in India

The present study relates to the influence of hydraulic shock loads and total dissolved solids (TDS) on the performance of three large-scale common effluent treatment plants (CETPs) treating textile effluents, which is generated from clusters of small-scale industries in the state of Rajasthan in India. Of the three CETPs, two having capacities 7.0 and 9.0 million liters per day (mld) are located in Pali and one of capacity 6.0 mld in Balotra, District Barmer. Wastewater from about one thousand small-scale industries is treated in these CETPs. The effects of hydraulic shock loads and TDS on effluent data from secondary clarifier for parameters biochemical oxygen demand (BOD) and suspended solids (SS) for CETPs at Pali, and chemical oxygen demand (COD) and SS for the CETP at Balotra were studied. It was observed that the effluent BOD and SS remained within the prescribed limits for CETP Pali at 30% increased flow rate, whereas effluent COD and SS at 30% increased flow rate for CETP Balotra exceeded the prescribed limits and the CETP could sustain 20% increased flow rate. The shock loading analysis revealed that CETP Balotra had reduced capacity to sustain shock loads by 10% as compared to CETP Pali due to the presence of high TDS (15,000-20,000 mg/l). High TDS interfered with the oxygen transfer necessary for biological metabolism, thereby affected the efficiency of activated sludge process. Hence, activated sludge process treating high TDS effluents are more sensitive to hydraulic shock loads and prone to process upsets.