The removal of color and COD from wastewater containing water base color by coagulation process

In this study acrylic water base color was removed from synthetic wastewater using coagulation process. Experiments were conducted on the sample containing 100 mg/L and 400 mg/L of acrylic water base color. Destruction of color by means of coagulation/flocculation techniques using ferrous sulfate, alum, lime and polyelectrolyte (cationic, anionic and non ionic). The study was performed in a systematic approach searching optimum values of alum and FeSO₄ concentration, pH and temperature. All the experiments were run in a laboratory scale.The obtained results show that treatment with alum and ferrous sulfate alone proved to be very effective in removing the color (> 99 %) and part of COD (60–70 %) from aqueous solution. Lime alone did not significant change on COD and color removal.     

Phosphate removal using compounds prepared from paper sludge and fly ash

Using waste as a resource to control phosphate pollution is a rising trend. This study describes the use of paper sludge (PS) and fly ash (FA), industrial solid wastes, to prepare materials with high phosphate uptake efficiency. The process consisted of pretreatment (mechanical milling), calcination, acidification (HCl), and post-treatment (aging, drying and grinding). The maximal phosphate uptake (>92 %) was achieved using PS together with FA either at PS/FA = 0.5 g/g or at PS/FA = 2.0 g/g, both calcined at 900 °C for 2 h and stirred with HCl (HCl/FA = 3 mL/g) for 1 h. With increasing calcination temperature and decreasing acid, the crystallinity of samples declined, and phosphate uptake (PU) increased. The PU process could be well described by the pseudo-second order kinetic model, while equilibrium state could be reasonably modeled by Langmuir isotherm. Neutral and weak alkaline pH promoted the PU efficiency, and 0.3 g sample/100 mL was the cost-effective dosage under the experimental conditions. The enhanced phosphate uptake of PS and FA provides alternative materials for phosphate removal from wastewater by the use of solid wastes in paper-making industries.     

Water treatment for color and COD removal by electrochemical oxidation on boron-doped diamond anode

The electrochemical oxidation of synthetic wastewater which contains biazo dye [amido black (AB)] on boron-doped diamond anode, “BDD anode,” was experimentally investigated to determine the influence of several operative parameters on the performance of the process. The study focalized on the effect of studied parameters on discoloration process and the degradation of the aromatic part of the dye molecule. Two distinct pathways with two different kinetics were observed. The decrease of pH improves the discoloration rate and the degradation of aromatic by-products after 90 min of electrolysis. The increase of current density has a considerable effect on discoloration and a little less effect on the aromatic derivative degradation. Hypochlorite electrogenerated from chloride addition exceptionally accelerates the discoloration, but it does not degrade aromatic derivatives as efficiently. It was observed that nitrates addition generates under electrolysis other derivates of AB as different colors than the dye one. The current efficiency depends very little on the initial pH; however, higher energy consumptions are obtained.     

Innovative anaerobic upflow sludge blanket filtration combined bioreactor for nitrogen removal from municipal wastewater

In this research, a novel laboratory scale anaerobic/upflow sludge blanket filtration combined bioreactor was designed and operated to improve the efficiency of the upflow sludge blanket filtration process for the simultaneous removal of phosphorus and nitrogen from wastewater. The anaerobic/upflow sludge blanket filtration technique was developed by adding an anaerobic reactor to its influent and operated by varying the main process parameters in order to gain the optimum conditions. The results showed that biological removal efficiency of nitrogen and preservation of sludge blanket strongly depend on wastewater characteristics, hydraulic retention time, sludge age and process controlling parameters. The combined bioreactor performed a total nitrogen removal efficiency of 96.6 % with the sludge age of 25 days, total hydraulic retention time of 24 h and optimum “chemical oxygen demand/nitrogen/phosphorus” ratio of 100/ 5/1. This ratio also improved the compaction quality of sludge blanket in the upflow sludge blanket filtration clarifier. The average specific nitrification and denitrification rates occurred during the process can be expressed as 4.43 mg NO_x-N produced/g VSS.d and 5.50 mg NOx-N removed/g VSS.d at the optimum ratio, respectively. To avoid sludge rising due to denitrification process, the optimum total hydraulic retention time of 16 to 24 h was achieved based on the effluent quality. This study suggested that the anaerobic/upflow sludge blanket filtration bioreactor at the optimum operational conditions can be an effective process for removal of nutrients from municipal wastewater.     

纸浆渣烧结灰基本特性及其在污泥固化中的试验研究

国内每年产生大量的污泥,其无害化处理、废物重新利用的技术是解决疏浚污泥污染问题的必由之路,而污泥固化技术是其重要的途径。纸浆渣烧结灰自身所具有的吸水性和自硬性是一种研制廉价污泥固化剂配方的重要成分,是把造纸产业废弃物和生产废弃物同时再利用的环保工法,具有现实的研究价值。对纸浆渣烧结灰基本特性进行了试验研究,并在此基础上进行了污泥固化的试验研究,主要包括纸浆渣烧结灰酸碱度试验、吸水率试验、微观结构试验、抗剪强度试验和污泥固化土的无侧限抗压强度试验,结果表明,纸浆渣烧结灰呈弱碱性;吸水性随着压力的增大而减小,存在一个最小吸水率;抗剪强度随含水率的增加而减小,且具有自硬性。纸浆渣烧结灰可提高水泥固化污泥的无侧限抗压强度,并且水泥的掺入含量越高,其强度的提高越显著。     

Pb and Co removal from paint industries effluent using wood ash

The release of heavy metals into the environment is a worldwide major concern. Different studies have demonstrated that natural agents have a high removal capacity for divalent heavy metal ions. Wood ash is a natural adsorbent and, in comparison with others, has a very low price. In this study, the removal of heavy metals (Pb and Co) from Binalood paint industry (Kerman, Iran) effluent was investigated in batch condition. Pb and Co measurement in samples were done with atomic absorption equipment and test methods were adapted from standard methods for the examination of water and wastewater. The effect of pH and the amount of adsorbent was determined and different adsorption isotherms were also obtained. This study shows that the adsorption process follows the adsorption Langmuir isotherm. The amount of wood ash has a great role in the adsorption rate and adsorption rate increased as wood ash increased. In the study, the reactions reached equilibrium in 3 h contact time. The maximum Pb removal efficiency was 96.1 % at pH 2 with a contact time of 3 h and 100 g/L wood ash and the maximum Co removal efficiency was 99 % at pH 2 with a contact time of 3 h and 100 g/L wood ash. According to the results, wood ash is recommended as a low cost and available adsorbent to remove Pb and Co from municipal and industrial wastewaters.     

Treatability of landfill leachate by combined upflow anaerobic sludge blanket reactor and aerated lagoon

Continuous upflow anaerobic sludge blanket reactor performs more favorably at the higher organic loading rate than other anaerobic treatment. The treatment of municipal landfill leachate of Shiraz??s city investigated using continuous flow anaerobic reactor and subsequently aerated lagoon. Landfill leachate has chemical oxygen demand of 45,000?C90,000?mg/L and ammonia nitrogen at 1,000?C2,500 and heavy metals that can impact biological treatments. Capacity of anaerobic and aerobic reactors is 10 and 20?L that operated at detention time of 2 and 4?days, respectively. Organic loading rate of upflow anaerobic sludge blanket is between 0.5?C20?g chemical oxygen demand/L/day. Chemical oxygen demand removal efficiencies are between 57?C87, 35?C70 and 66?C94% in the anaerobic, aerobic and whole system, respectively. As the entry, leachate organic loading rate increased from 1 to 20?g/L/day, the chemical oxygen demand removal efficiency reached a maximum of 71% and 84% in the anaerobic reactor and whole system, respectively, at high organic loading rate. Ammonium removal efficiency was about 54% after the aerobic stage.     

Biosorption of 4-chlorophenol by dried anaerobic digested sludge: artificial neural network modeling,equilibrium isotherm,and kinetic study

In this study, dried anaerobic digested sludge (DADS) was utilized to remove 4-chlorophenol (4-CP) from aqueous solutions. Batch biosorption experiments were carried out to investigate the effects of physicochemical parameters such as pH, contact time, biosorbent dosage, and initial concentration. Artificial neural network (ANN) was then used to predict the removal efficiency of the process. The comparison between predicted and experimental results provided a high degree of determination coefficient (R² = 0.98), indicating that the model could predict the biosorption efficiency with reasonable accuracy. Biosorption data were successfully described by the Freundlich isotherm and pseudofirst-order model. The Weber–Morris kinetic model indicated that intraparticle diffusion was not the only rate-controlling step, and other mechanisms may be involved in the biosorption process. The optimum pH was detected to be 3 for DADS. By increasing contact time and biosorbent dosage, the removal efficiency of 4-CP increased. Also, a decreasing trend was observed when initial concentrations were increased. The findings suggested that the results predicted by ANN are very close to the experimental values, and DADS as an available adsorbent can efficiently remove 4-CP from aqueous solutions.     

Nutrient removal from activated sludge mixed liquor by wastewater protozoa in a laboratory scale batch reactor

The aim of the study was to investigate the nutrient removal rate of three wastewater protozoan isolates. The study was carried out in a laboratory-scale batch reactor for a period of 120 h. in a four batch study. Aliquot samples were withdrawn from the reactor every 24 h. for the analysis of phosphate, nitrate, nitrite, ammonia, chemical oxygen demand, dissolved oxygen and pH, using standard methods. The results obtained in the different batches among the three isolates showed PO₄ ^2? removal rate ranging from 0.04 to 0.52 mg-PO₄ ^2?/L/h. while NO₃ ^? nitrate removal rates ranged from 0.08 to 0.16 mg-NO₃ ^?/L /h. Also NO₂- and NH₃ rates were observed to range between 0.022 and 0.087 mg-NO₂ ^?/L /h. 0.05 and 0.16 mg-NH₃ ^?/L /h, respectively. For the physicochemical parameters, there was no observed COD decrease; rather there was an increase and this was irrespective of isolates and experimental batches. However, dissolved oxygen concentration decreased drastically (below 1 mg/L) at the end of each batch while pH show a decrease after an initial 24 h. period and thereafter increased. This trend was also irrespective of isolates and experimental batches. Overall, the study has been able to show the effect of the test isolates on nutrient removal rates and other physicochemical parameters (COD, DO and pH) in activated sludge mixed liquor.     

反硝化菌的耐砷驯化及其对水铁矿吸附态砷迁移转化的影响

采集缺氧活性污泥进行室内微生物驯化,培养耐砷反硝化菌。把耐砷反硝化菌、营养液和吸附As(V)的水铁矿在厌氧条件下培养,研究反硝化菌代谢作用下,系统中Fe、Mn、NO3-和As形态的动态变化。结果表明,缺氧活性污泥中的反硝化菌具有一定的耐砷能力。在砷含量500μg/L以内,其反硝化强度基本不受砷的影响。在吸附有砷的水铁矿体系中,反硝化菌所产生的反硝化作用可导致溶液中NO3-含量的降低、Fe含量的升高、As含量降低,且As(III)所占比例增加。这说明,体系中水铁矿的还原性溶解和As(V)的还原性解吸已经发生。As含量降低的原因是,在培养体系中水铁矿的含量高,Fe的释放量只占很小比例,表层水铁矿被还原后,在次表层形成新的水铁矿吸附位,这种新吸附位不仅可以吸附溶液中已经存在的As,而且能够再吸附由于还原性溶解和解吸所释放出的As。     

Preservation of thermophilic mixed culture for anaerobic palm oil mill effluent treatment by convective drying methods

The generation of huge amount of liquid waste known as palm oil mill effluent is a major problem in oil palm industry. Meanwhile, anaerobic biodegradation of such organic effluent at thermophilic condition is a promising treatment technology due to its high efficiency. However, storage and transportation of thermophilic mixed culture sludge are challenging due to constant biogas generation and heating requirement. Hence, drying of thermophilic sludge was conducted to obtain dormant thermophiles and thus enables easier handling. In this study, thermophilic sludge was dried using heat pump at 22 and 32 °C as well as hot air oven at 40, 50, 60, and 70 °C. Subsequently, quality of dried sludge was examined based on most probable number enumeration, chemical oxygen demand, and methane yield. Average drying rate was found to increase from 3.21 to 17.84 g H₂O/m² min as drying temperatures increases while average moisture diffusivity values ranges from 5.07 × 10^?9 to 4.34 × 10^?8 m²/s. Oven drying of thermophilic mixed culture resulted in highest chemical oxygen demand removal and lowest log reduction of anaerobes at 53.41% and 2.16, respectively, while heat pump drying resulted in the highest methane yield and lowest log reduction of methanogens at 53.4 ml CH₄/g COD and 2.09, respectively. To conclude, heat pump at 22 °C was most suitable drying technique for thermophilic mixed culture as the original methane-producing capability was largely retained after drying, at a slightly lower yet still comparable chemical oxygen demand removal when palm oil mill effluent was treated with the rehydrated culture.     

Value addition of paper coating grade kaolins by the removal of ultrafine coloring impurities

Two kaolin samples from the southern part of Kerala (A and B) have been characterised. The colouring impurities present were found to be carbonaceous and ferruginous, being also present in ultrafine size ranges. Modern beneficiation techniques such as ultra flotation and high gradient magnetic separation (HGMS) have been carried out to reduce the level of these contaminants and to increase the brightness of the product clays. The results showed that nearly 70% of the ultrafine carbonaceous matter in A, which originally contains 0.13% carbon (as fixed carbon), could be removed by shear floc-flotation. HGMS treatment could remove ∼ 45% of the iron minerals (feed assay 0.58% Fe₂O₃). Sample B contained 0.32% Fe₂O₃ and 0.19% carbon. The shear floc-flotation was found to be the only effective method by which ∼ 75% of the carbon could be floated out. This sample did not respond to HGMS which may be because of the ‘structural’ nature of the iron present. Both the kaolins, after processing, were found suitable for paper coating. Another important aspect of this work is the establishment of maximum permissible level for carbon in paper coating grade clays since the standard specifications do not give any limiting value.     

Adsorption kinetic studies for removal of methylene blue using activated carbon prepared from sugar beet pulp

Sugar beet pulp is an abundant, renewable and low-cost precursor for production of activated carbon. In the present study, sugar beet pulp based activated carbon was prepared by using phosphoric acid as activating agent for adsorption of methylene blue. The conditions of preparation process had a significant influence on the adsorption of methylene blue, and the optimal preparation conditions were obtained as follows: liquid-to-solid ratio of 5, temperature of 450 °C and phosphoric acid concentration of 3 mol/L. The properties of sugar beet pulp based activated carbon were characterized by nitrogen adsorption isotherm. The adsorption increases as the increase of contact time, adsorption temperature and pH, and initial concentration of methylene blue. Batch kinetic studies showed that an equilibrium time of 100 min was needed for the adsorption, and the adsorbance of methylene blue is 244.76 mg/g at equilibration. Kinetic models, Weber’s pore diffusion model and Boyd’s equation were applied to the experimental data to study the mechanism of adsorption and the controlled step. The results showed that the adsorption kinetics followed the pseudo-second-order type kinetic model, intraparticle diffusion was not the rate-limiting mechanism and adsorption process was controlled by film diffusion.     

A safe haven of SARS-CoV-2 in the environment: Prevalence and potential transmission risks in the effluent,sludge, and biosolids

The novel coronavirus, SARS-CoV-2, which has caused millions of death globally is recognized to be unstable and recalcitrant in the environment, especially in the way it has been evolving to form new and highly transmissible variants. Of particular concerns are human-environment interactions and the handling and reusing the environmental materials, such as effluents, sludge, or biosolids laden with the SARS-CoV-2 without adequate treatments, thereby suggesting potential transmission and health risks. This study assesses the prevalence of SARS-CoV-2 RNA in effluents, sludge, and biosolids. Further, we evaluate the environmental, ecological, and health risks of reusing these environmental materials by wastewater/sludge workers and farmers. A systematic review of literature from the Scopus database resulted in a total of 21 articles (11 for effluents, 8 for sludge, and 2 for biosolids) that met the criteria for meta-analysis, which are then subdivided into 30 meta-analyzed studies. The prevalence of SAR-CoV-2 RNA in effluent and sludge based on random-effect models are 27.51 and 10^12.25, respectively, with a 95% CI between 6.14 and 48.89 for the effluent, and 10^4.78 and 10^19.71 for the sludge. However, the prevalence of SARS-CoV-2 RNA in the biosolids based on the fixed-effect model is 30.59, with a 95% CI between 10.10 and 51.08. The prevalence of SARS-CoV-2 RNA in environmental materials indicates the inefficiency in some of the treatment systems currently deployed to inactivate and remove the novel virus, which could be a potential health risk concern to vulnerable wastewater workers in particular, and the environmental and ecological issues for the population at large. This timely review portends the associated risks in handling and reusing environmental materials without proper and adequate treatments.     

Physical protection of lignin by organic matter and clay minerals from chemical oxidation

The role of organic matter (OM) concentration, structure and composition and how these relate to mineral protection is important for the understanding of long term soil OM dynamics. Various OM–clay complexes were constructed by sequential sorption of lignin and dodecanoic acid to montmorillonite. Humic acid–montmorillonite complexes were prepared at pH 4 and 7 to vary OM conformation prior to sorption. Results obtained with constructed OM–clay complexes were tested with isolated mineral fractions from two soils. Oxidation with an acidic NaClO₂ solution was used to chemically oxidize lignin in the OM–clay complexes, sand-, silt- and clay-size soil fractions to test whether or not it can be protected from chemical attack. Gas chromatography–mass spectrometry was used to analyze lignin-derived phenols, cutin OH–acid (after CuO oxidation), fatty acid and n-alkanol concentrations and composition. We found that carbon content was not solely responsible for lignin stability against chemical oxidation. Lignin was protected from chemical oxidation through coating with dodecanoic acid and sorption of humic acid to clay minerals in a stretched conformation at pH 7. Therefore, interactions between OM constituents as well as OM conformation are important factors that protect lignin from chemical oxidation. Lignin-derived phenol dimers in the Grassland-Forest Transition soil fractions were protected from chemical oxidation to a greater extent compared to those in Grassland soil fractions. Therefore, although lignin was protected from degradation through mineral association, the extent of this protection was also related to OM content and the specific stability of lignin components.     

Utilization of palm oil mill effluent for polyhydroxyalkanoate production and nutrient removal using statistical design

The optimization for poly-β-hydroxyalkanoate production was carried out with nutrient removal efficiency for total organic carbon (TOC), phosphate, and nitrate from palm oil mill effluent waste. The experiment was conducted in a fabricated fed-batch reactor and the data obtained was analyzed using central composite rotatable design and factorial design for response surface methodology as a systematic approach for designing the experiment statistically to obtain valid results with minimum effort, time, and resources. The analysis of numerical optimization with propagation of error showed that 66 % of poly-β-hydroxyalkanoate production can be obtained with nutrient removal of TOC and nitrate by 19 and 3 %, respectively. However, phosphate removal efficiency was not found to be much effective. More over, the chemical oxygen demand: nitrogen phosphate (509 g/g N), chemical oxygen demand: phosphate (200 g/g P), air flow rate (0.59 L/min), substrate feeding rate (20 mL/min), and cycle length (20 h) were the optimized variables for maximum poly-β-hydroxyalkanoate production and nutrient removal.     

Historical variations in the stable isotope composition of mercury in a sediment core from a riverine lake: Effects of dams,pulp and paper mill wastes,and mercury from a chlor-alkali plant

The Wabigoon River (Ontario, Canada) was affected by dams starting in 1898 and was polluted with pulp and paper mill wastes starting in 1913 and mercury from a chlor-alkali plant from 1962 to 1975. A dated sediment core from a riverine lake was analysed to investigate resultant changes in the biogeochemistry of mercury as revealed by variations in mercury isotope ratios and sediment chemistry. A total mercury maximum formed by the mercury pollution coincided with minimums in the δ-values of the ¹⁹⁸Hg/²⁰²Hg, ¹⁹⁹Hg/²⁰²Hg, ²⁰⁰Hg/²⁰²Hg, and ²⁰¹Hg/²⁰²Hg ratios, and the δ-values decreased in the order δ²⁰¹Hg > δ²⁰⁰Hg > δ¹⁹⁹Hg > δ¹⁹⁸Hg. Thus, mass-dependent fractionation caused depletion in lighter isotopes, implying evaporation of Hg(0) and pollution of the atmosphere as well as the river-lake system. Concurrently, mass-independent fractionation caused ¹⁹⁹Hg enrichment, possibly reflecting an independently documented upsurge in methylmercury production, and ²⁰¹Hg depletion, suggesting removal of methylmercury with anomalously high ²⁰¹Hg/¹⁹⁹Hg ratios by aquatic organisms and accumulation of ²⁰¹Hg-depleted inorganic Hg(II) in sediments. The δ²⁰¹Hg/δ¹⁹⁹Hg ratio rose abruptly when mercury pollution began, reflecting the resultant increase in methylmercury production, and remained high but gradually declined as the pollution abated, paralleling trends shown by methylmercury in aquatic organisms. The δ²⁰¹Hg/δ¹⁹⁹Hg ratio of pre-1962 background mercury increased ca. 1898 and ca. 1913–1929, suggesting accelerated methylmercury production due to stimulation of microbial activities by the damming of the river and the input of pulp and paper mill wastes, respectively. Other variations were linked to economic and technological factors that affected pulp and paper manufacture.     

Evaluation of mineral substrates for in situ iron removal from groundwater

Calcium carbonate-based materials (CCBM) have been found to remove Fe(II) and other divalent metal cations from aqueous solution and thus have the potential for incorporation into remediation systems to remove Fe(II) from groundwater at landfills. Research was conducted to examine the ability of a range of CCBM to remove Fe(II) and assess the mechanism of removal. Different CCBM (limestone, concrete, dolomite, marble), as well as gypsum, witherite, and quartz sand, were tested for their ability to remove Fe(II) from water using batch tests conducted under anaerobic conditions. Limestone (specific surface area of approximately 0.46 m²/g) was found to have the best removal effectiveness, and the final Fe(II) concentration was reduced from 50 to <0.01 mg/L. Kinetics experiments conducted over a 72 h period indicated that the removal process of Fe(II) by CCBM was a two-step process. The first step is rapid sorption of Fe(II) onto the CCBM surfaces within the first hour, and the second step is relatively slow co-precipitation of iron-containing solids formed through various chemical reactions. The two best performing CCBM (limestone and concrete) were evaluated for their removal ability based on media particle size (diameters of 3–5, 7–10, 15–25, and 40–50 mm) and revealed statistically significant (p < 0.01) increases in Fe(II) removal for each particle size class examined. SEM analysis of reacted materials revealed visible precipitates on the reactive material surface; XRD analysis was not able to detect crystalline Fe minerals on limestone surface.     

Accumulation of lead, cadmium, manganese, copper and zinc by sludge worms; Tubifex tubifex in sewage sludge

Tubifex tubifex has been shown to survive in organic polluted environments, however, not much has been done on its inorganic pollution tolerance. Samples of T. tubifex and their respective sewage sludge were taken from Soche wastewater treatment plant in Blantyre City, Malawi during July 2007 to November 2008. The total number of sludge samples taken was fifty one which was made into seventeen composite samples. A total of seventeen T. Tubifex samples were also collected. The samples were analyzed for copper, lead, manganese, zinc and cadmium using standard methods from American Public Health Association and Association of Official Analytical Chemists. The concentrations of metals in sewage sludge and T. tubifex were on dry weight basis and the metals determined were acid extractable. In general, heavy metals concentration was lower in T. tubifex than in sewage sludge. The range of heavy metals concentrations were (in sludge and (T. tubifex)): zinc 275.3–361.5 mg/kg (45.0–82.2 mg/kg), manganese 293.7–230.1 mg/kg (1.21–3.69 mg/kg), copper 86.5–120.1 mg/kg (1.6–4.7 mg/kg), lead 11.2–22.4 mg/kg (Below detection limit–0.95 ) and cadmium 1.12–2.31 mg/kg (1.08–2.18 mg/kg). The results showed significant differences between the concentrations of manganese, copper, lead and zinc in sewage sludge and T. tubifex (p < 0.05). However there was no significant difference between the concentrations of cadmium in sewage sludge and T. tubifex (p > 0.05). T. tubifex did not show the ability to accumulate heavy metals (attributed to its high defecation and metabolic rate) except for cadmium hence cannot be used as a bioindicator for heavy metal pollution in sludge.