No abstract

No abstract

No abstract

No abstract

This study focuses on the dynamic behavior of ammonium ion uptake during continuous operation with respect to liquid by means of ion exchange with a natural zeolite in fluidized and segregated fluidized beds. The major operating variables affecting the performance in both types of fluidized beds are particle size, bed expansion, and flow rate. Use of particles of about 300 μm size in monodispersed fluidized beds resulted in breakthrough capacities of about 0.5 meq/g or higher, with contact times in the order of 0.7À5.5 min. The column efficiencies in terms of breakthrough capacity/total capacity were in the order of 0.42À0.61. The segregated fluidized bed, as achieved by using two nonmixing particle size fractions, is a hybrid fluidized bed consisting of an expanded bed with reduced mixing which is topped by a regular fluidized bed. Segregation increased the column efficiency to 0.69 when a combination of 250À300 and 500À600 μm sized particles were fluidized with a contact time of 1 min. The breakthrough capacities for the segregated fluidized beds with the finer particle size combination were 0.60À0.89 meq/g. A new representation of the breakthrough curves in terms of C/C 0 versus a dimensionless time t/t f suggests that these plots are a valuable tool for comparing performances for a wide variety of experimental conditions. The results of this study indicate that fluidization can well be applied to ion exchange operations to accommodate high influent flow rates.

Crushed recycled glass as a filter medium and comparison with silica sandThe objective of this work was to evaluate crushed recycled glass as a medium for rapid filtration. In the first part of this work, physical and hydraulic characteristics of the glass medium were studied. In the second part, pilot scale inline filtration experiments were carried out using raw waters from three different water sources. Two physically identical filter columns were operated in parallel in all the experiments. One filter contained a silica sand medium that is widely used in Turkey, whereas the other filter contained crushed recycled glass. Experiments were repeated five times as follows: (i) Without the use of a coagulant, (ii-iii) with 5 mg/L and 10 mg/L of alum, and (iv-v) with 5 mg/L and 10 mg/L of ferric chloride. Turbidity, particle counts, and head losses were measured and compared as functions of time. The following were observed: (1) Provided that a coagulant was used, the filter containing crushed glass produced effluent turbidities and particle counts similar to those obtained with the sand filter. (2) The crushed glass medium generated both a smaller clean-bed head loss and smaller clogging head losses than those of the sand filter. It is concluded that crushed glass shows significant promise as an alternative to silica sand in rapid filtration.

Crushed recycled glass was evaluated as an alternative to silica sand in dual‐media filters. Pilot scale inline filtration experiments were carried out using raw waters from three different water sources with turbidities between 6.0 and 14.0 NTU. Two physically identical filter columns were operated in parallel in the experiments. One filter consisted of 62.5 cm silica sand and 41.5 cm anthracite coal, whereas the other filter contained 62.5 cm crushed recycled glass plus 41.5 cm anthracite coal. The total bed depth was 104 cm for both filters. The properties of the media were as follows: Glass effective size = 0.77 mm, uniformity coefficient = 1.41. Sand effective size = 0.79 mm, uniformity coefficient = 1.33. Coal effective size = 1.45 mm, uniformity coefficient = 1.39. Experiments were repeated five times as follows: (i) Without the use of a coagulant, (ii–iii) with 5 and 10 mg/L of alum, and (iv–v) with 5 and 10 mg/L of ferric chloride. The filtration rate used was 11.5 m/h. Turbidity, particle counts, and head losses were measured and compared as functions of time. The following were observed: (i) Effluent turbidities and particle counts of the two filters were very close, i.e., essentially the same effluent quality was obtained when crushed glass was used instead of silica sand. (ii) In the majority of the tests, the filter with crushed glass generated both a smaller clean‐bed head loss and smaller clogging head losses than those of the filter containing sand. It is concluded that crushed glass may be a good alternative to silica sand in dual‐media filtration.

The influences of pH and ammonia on methane production in the anaerobic treatment of an acetic-propionic-butyric acid mixture in batch reactors operated at 37 degrees C were investigated. Two independent sets of experiments were carried out using seeds from two different full-scale industrial anaerobic treatment reactors. One of the seeds ("Sludge A") was obtained from an upflow anaerobic sludge-blanket (UASB) reactor treating the waste from a potato chips production plant. The second sludge seed ("Sludge B") was from an expanded granular sludge-blanket (EGSB) reactor treating a corn processing waste. Experiments were carried out at four different pH values (6.8, 7.4, 7.8, 8.4) and with six different TAN (Total Ammonia Nitrogen) values (262mg/L (control), 1000, 1500, 2000, 2500, 3000). Three vials (triple runs) were used for each pH and TAN value. The sludge seeds used in the inhibition tests were not exposed to high levels of ammonia at any stage before the tests. For each vial, cumulative methane production was monitored for a period long enough for the termination of biogas production. Although neither sludge was acclimated to ammonia, the lag-phase times were less than 2 days for Sludge A and essentially zero for Sludge B for all TAN and pH values. At certain high pH and high TAN values, however, methanogenic activity ceased within about 1-3 months; and then activity restarted and methane formation rate reached its maximum values after this period. If the experiments had not been continued following this period, this reactivation phenomenon would not have been detected.