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Arsenic-polluted water is a global concern and puts millions of people at risk of developing cancer. The improvement of aqueous solution coexisting with arsenite and arsenate using iron mixed porous clay pellets was investigated in batch and fixed-bed column systems. Batch studies showed that the removal rate occurred in two main phases with an equilibrium time of 52 h. The pseudo-second-order model well described the experimental data. Isotherm data were well fitted by the Langmuir–Freundlich model. The removal efficiency was significantly reduced in alkaline solution and the presence of phosphate ions. The column study revealed that the breakthrough time and saturation time increased with lower feeding flow rate, higher bed height, and lower initial adsorbate concentration. The Thomas model provided good performance for predicting the column experimental data.

Many people in Cambodia consume groundwater with arsenic concentrations above the WHO guideline. In this study, an iron-mixed porous pellet adsorbent was put into a lightweight bio-sand filter to treat arsenic. The filter was intermittently charged daily with 30 L influent water until the effluent arsenic concentration exceeded 10 μg/L. The results indicated that the Morrill Dispersion Index was less than 2.0, implying that the filter had preferential plug flow. Head loss accumulation led to flow rate reduction over a period of 30 days. Arsenic removal efficiency was between 97 and 99% for the influent concentration, being in the range 355 to 587 μg/L. No significant leaching of iron or organic carbon was observed. The high dissolved oxygen concentration is likely to have contributed to the aerobic conditions in the filter bed. The filter removed arsenic more efficiently than was achieved in some previous studies and might be suitable to provide household-scale, arsenic-safe drinking water.

The excess sludge problem from a wastewater treatment plant is a great concerned due to the high cost of sludge management accounting for about 20% to 50% of the total operating cost. Therefore, sludge reduction is critical. Currently, aerobic and/or anaerobic sludge digestions are widely used in the industries for treating the excess sludge. The objective of this research was to study the effects of aeration rate and temperature on the excess sludge reduction by using the aerobic-anaerobic digestion system in the laboratory. The aeration rates of 1.0, 0.5, and 0.1 volume air per volume slurry per minute (vvm) at the room temperature and the thermophilic temperature (55 ± 2°C) were investigated. The results showed that the highest removal efficiency of aerobic sludge digestion was obtained at the thermophilic temperature and aeration rate of 1.0 vvm. The removal efficiency of organic matter in terms of COD, total solids (TS) and volatile solids (VS) were 34.76%, 33.01% and 43.45%, respectively. Consequently, the highest specific growth rate of microorganisms was 0.39 per hour and the substrate removal rate was 0.55 milligram CODremoved per milligram VSS per hour. Furthermore, slowly biodegradable organic matter was hydrolyzed to readily biodegradable organic matter and inert soluble organic matter. When the sludge effluent from aerobic sludge digestion was feed to the anaerobic sludge digestion, the removal efficiency of organic matter in terms of COD, TS and VS were increased by 25%, 17% and 28%, respectively. Moreover, the obtained methane production rate in the anaerobic sludge digestion was approximate 0.234 m3/kg COD removed.

Textile wastewater is a considerable source of environmental contamination due to its strong color, high pH and chemical oxygen demand (COD), and low biodegradability. The discharge of textile wastewater not only has diverse aesthetic effects, but such discharge can be carcinogenic, mutagenic and generally detrimental to our environment. Thus, textile wastewater should be removed completely before they are discharged into received water. Many methods have been reported for treating textile wastewater, among which coagulation and adsorption are widely used processes due to their relatively simple operation and low costand suitable for household industry. The aim of this study was using the combination coagulation and adsorption processes to treat textile wastewater in household-scale industry. Coagulation performance and removal efficiencies in COD and color from four varies sources of textile wastewaters were investigated. The effluent from coagulation was treated with adsorption. The adsorption isotherm and removal efficiencies were investigated. The results showed the combination processes had the overall COD were in the range of 72.9-93.8% and color removal efficiencies were in the range of 70.6-98.5%. The results of coagulation study were found that in some cases of wastewater were effective in color removal but failed in COD removal, in another case, had failed in color but were effective in COD removal efficiencies. The results showed varies of pH had much affected on color removal efficiencies more than COD removal efficiencies. The further experiments should be carried out to improve the combination removal efficiencies for application as suitable for textile household industry.

Natural clay combing with iron oxide and iron particle was developed to be iron-mixed mesoporous pellet that was packed in a fixed-bed column for removing arsenic from water. The performance of the column in terms of breakthrough curve analysis was investigated with the variations of influent flow rate, adsorbent bed height, initial solution pH, and initial adsorbate concentration. The results indicated that increasing in the flow rate decreased the removal capacities of the adsorbent. A relatively low bed height provided a better and beneficial performance. Higher adsorption capacity was observed with an increase of initial adsorbate concentration. At higher initial solution pH, the repulsive process occurred between adsorbate species and the surface charge of the adsorbent, resulting in a poor performance of the column. The Thomas model fitted very well to the experimental data for all cases. Estimated from the model, the highest adsorption capacity for arsenite and arsenate was found to be about 509 and 430 μg/g, respectively. The Adam-Bohart model provided only a relatively satisfactory fit to the initial part of the experimental data. From a practical view, the new developed pellet could be used as the effective and efficient adsorbent to treat elevated arsenic contaminated groundwater.

In this study, natural clay, iron oxide, and iron powder were combined to develop low-cost iron mixed porous pellet adsorbent for arsenate and arsenite removal from aqueous solution in batch experiments. The augmented simplex centroid mixture design was applied to obtain the optimum proportion of each constituent. Higher correlation coefficient of the models (R2 > 0.95), good distribution of residuals, and lower values of p value ( 9). Kinetic and isotherm experimental data of both arsenate and arsenite were well described by the pseudo-second order and Sips models, respectively. The maximum adsorption capacity of arsenate and arsenite derived from Sips model were 13.33 and 19.06 mg/g, respectively. The separation and heterogeneity factors showed that both arsenate and arsenite were favorably adsorbed. Among coexisting anions, phosphate significantly showed negative effect on the adsorption of either arsenate or arsenite. The adsorbent could be effectively reused for several times after its regeneration and was considered as non-hazardous material after adsorption.

Millions of people in more than 70 countries are at risk of developing arsenicosis and otherhealth issues due to consuming elevated arsenic contaminated water. The present study aimed to use naturalclays heated at high temperature and treated with ferrous and ferric solutions through a simple coatingtechnique enhanced by moderate temperature for arsenate uptake from water. BET, XRF, XRD and SEMmethods were applied for the adsorbent characterization. Adsorption experiments were conducted in a seriesof batch systems in terms of contact time, solution pH, initial concentration and the presence of coexistinganions. The results indicated that the adsorption kinetics was better described by the pseudo-second order ratemodel for all adsorbents. All adsorbents exhibited higher arsenate uptake efficiency in the acidic condition.Langmuir model provided the maximum arsenate adsorption capacity of 250µg/g, 429.74µg/g and747.38µg/g for calcined clay (MC), ferric calcined clay (MC-FeIII) and ferrous calcined clay (MC-FeII),respectively. Among added coexisting anions, phosphate (PO3-) significantly decreased the arsenateadsorption capacity of all adsorbents. Overall, regarded to a wide availability of raw materials, simplicity ofthe modification and improvement of arsenate adsorption capacity, modified natural clay adsorbents,especially MC-FeII, could be considered to be effective and low-cost to remove arsenate from water.

Slow degradation of waste activated sludge (WAS) is a disadvantage of anaerobic digestion leading to high sludge retention time in conventional digesters. So, this study was proposed to increase biodegradability of WAS by alkaline pretreatment, and effect of pretreatment on the performance of anaerobic digestion and treatment efficiency was evaluated under both ambient and thermophilic condition. The soluble chemical oxygen demand (SCOD) and biochemical oxygen demand (BOD) fractions increased when pH values were increased. The solubilization had the highest increase in the pH range of 11 to 12 and gradually increased in the pH range of 8-11. However, the BOD 20 /COD ratios decreased for adjusted pH 10 and pH 11, and biodegradation was limited at pH 12. And pH 8 was the optimal value this alkaline pretreatment on anaerobic digestion. In alkaline pretreatment thermophilic anaerobic condition (PTAN), the result remove were 42.16%, 43.15% and 50.64% for TS, VS and COD removal, respectively, which are higher efficiency and gas production when compared to other conditions.

Broken mesoporous ceramic filter was reutilized by coating with ferric solution through a simple loading method enhanced with heating at a moderate temperature for arsenate uptake from aqueous solution. BET, XRF, XRD, and SEM methods were applied for the adsorbent characterization. The adsorption study was conducted in a batch mode to investigate kinetics, isotherms, and the effect of solution pH and co-existing anions. The pseudo-second order kinetic model well fitted the experimental data (R2 = 0.9997). The maximum arsenate adsorption capacity (2.27 mg/g) was derived from the better described Langmuir isotherm model (R2 = 0.9992). The adsorbent expressed high arsenate adsorption capacity over a pH range of 4-10. The uptake behavior is a favorable and physical adsorption process based on the value of separation factor and mean sorption energy. The presence of co-existing anions decreased the arsenate adsorption capacity in the following order: NO3-< SO42- < PO43-. The new ferric-coated mesoporous ceramic adsorbent could be an effective and low-cost adsorbent for arsenate removal from water.

This study is aimed at a performance evaluation of downflow hanging sponge (DHS) systems using mixed fungal and bacterial cultures for posttreatment of upflow anaerobic sludge blanket (UASB) effluents of tapioca starch wastewater. The effects of sludge composition on the microbial activity and effluent organic matter were also investigated. The whole experiment consisted of RUN I and RUN II with hydraulic retention times (HRTs) of 7 and 1 h, respectively, and the organic loading rates (OLR) ranged from 2.0 to 6.0 kg COD/m3 day-1 . The organic removal efficiencies were higher in RUN II, in the 94–96% range for both DHS systems. Under steady-state conditions, the volatile suspended solids (VSS) concentration in the sludge retained in the fungal downflow hanging sponge (FDHS) system showed little change, indicating a balance between the degradation of old biomass and the accumulation of the fresh biomass. Also, there was no significant removal of nitrogen in the FDHS system. However, the nitrogen was reduce...