Biomedical subjects

K V Lo

Publications and source records attributed to K V Lo.

12 recordsLinked to original sources

PubMed2006

Production and basic morphology of struvite crystals from a pilot-scale crystallization process.

A pilot-scale, struvite crystallization process was operated using anaerobic digester supernatants from two, full-scale, treatment plants as influent. It was found that the produced struvite crystals were easily separated from the process and were composed of very pure struvite (91.2 % to 94.1 % purity), with small amounts of calcium and carbonate, and traces of iron and aluminum. Most of the harvested struvite crystals, which were an aggregation of numerous fine crystals, were round, hard and larger than 1.5 mm in mean diameter. The crystal retention time in the reactor and the magnesium dosage in the supernatant appeared to have a significant effect on the crystal size, hardness and morphology.

Crystallization↗

PubMed2005

Rapid determination of total Kjeldahl nitrogen using microwave digestion.

A closed-vessel microwave digestion process for the determination of total Kjeldahl nitrogen (TKN) has been developed for sewage and wastewater. TKN values obtained from the microwave digestion method were in excellent agreement with those of the thermal digestion method. The accuracy of both analytical methods is comparable. In comparison to the conventional thermal digestion, the microwave method shortened the time required for complete digestion from 4 h to 25 min, and also decreased the maximum digestion temperature from 380 degrees C to 200 degrees C. This developed method may contribute to a significant reduction in sample digestion time, resulting in an increase in analytical throughput. The microwave digestion method developed in this study could be a rapid and efficient means for TKN determination for sewage wastewater and sludge.

Hot Temperature↗

PubMed2001

Activated sludge immobilization using the PVA-alginate-borate method.

The PVA-alginate-borate method was used successfully to immobilize activated sludge. The optimum polyvinyl alcohol (PVA) concentration in the immobilized sludge was determined to be 10-12.5%. A minimal alginate of 1% in the beads was needed to prevent bead agglomeration. If the pH of the saturated boric acid was adjusted to 7.0 prior to allowing droplets of the mixture of PVA, alginate and sludge to enter the solution, a high level of sludge activity could be maintained in the beads formed. During the continuous operation of a fluidized bed reactor, with hydraulic retention time (HRT) in the range of 24-3 h (BOD loading from 0.176 to 0.766 kg/d/m3) and an aeration rate at 1.0 L/min, more than 90% of BOD5, NH4(+)-N and TKN were removed. The immobilized sludge exhibited satisfactory mechanical stability without apparent breakage.

Alginates↗

PubMed2001

Domestic wastewater treatment using immobilized sludge fluidized-bed reactors.

Bench-scale fluidized-bed reactors using the immobilized activated sludge process were studied for the treatment of domestic wastewater. Different intermittent aeration patterns were investigated in order to improve the total nitrogen (TN) removal. The best TN removal at 74.4% was achieved at an HRT of 6 hours (with corresponding BOD loading rate of 0.766 kg/m3/d) and an aeration-pattern of 1,3 (the hours of aeration and non-aeration time cycle). The removal efficiencies for organic carbon, NH4(+)-N, TKN and TSS were not affected and remained at more than 90%. Simultaneous organic carbon and nitrogen removal was accomplished in a single immobilized sludge reactor. The impact of various influent feed patterns on the treatment was examined. The continuous feed pattern was recommended as it ensured good TN removal without any adverse impacts on the removal of organic carbon, NH4(+)-N, TKN and TSS. The immobilized sludge beads exhibited satisfactory mechanical stability without apparent breakage over the 180-day experiment period.

Bioreactors↗

PubMed2001

Biological treatment of pulp mill wastewater using sequencing batch reactors.

Lab-scale sequencing batch reactors were used to treat chemithermomechanical pulping wastewater that had chemical oxygen demand (COD) and biochemical oxygen demand (BOD) in the range of 5,980-8,990 mg/L, and 2,240-3,190 mg/L, respectively. A cycle time of 24 hour, with a hydraulic retention time of 34.3 hours was used. With 1 hour of settling, COD and BOD reductions of 30-41% and 67-78% were observed. However, with a 4-hour settling, COD and BOD reductions of 53-62% and 88-94% were achieved, respectively. Most of the oxygen demand reductions occurred within the first 16 hours of aeration. Adjustment of pH did not result in significant improvement in COD removal. Resin acids and fatty acids concentrations in the CTMP wastewater were reduced in the SBR process; however, they were still not fully detoxified in the effluent.

Biodegradation, Environmental↗

PubMed2001

Ammonia removal from composting leachate using zeolite. I. Characterization of the zeolite.

The effects of ammonium concentrations, contact time, and zeolite particle sizes on the ammonium adsorption capacities of a Canadian zeolite were studied using batch experiments. Both the rates and capacities of ammonium adsorption increased with increased concentrations of ammonium in solution. Ammonium adsorption increased significantly with decreasing zeolite particle size for all tests and the adsorption capacities ranged from 14.35-17.81 mg N/g. Also, ammonia adsorption increased with contact time, and it occurred rapidly at the beginning of contact, and then gradually decreased as time progressed. Langmuir isotherm best describes the equilibrium of ammonia adsorption on zeolite. Particle diffusion was the rate-controlling mechanism for the first 4 h of contact. In spite of competition potassium ions, zeolite has shown a great potential for ammonia removal from composting leachates.

Adsorption↗

PubMed2001

Ammonia removal from compost leachate using zeolite. III. Regeneration of zeolite columns.

The effects of hydraulic reteneration time (HRT), and the strength of the regenerating solution on the ammonia adsorption capacity and the zeolite regeneration were studied using bench-scale packed zeolite columns. A 0.6 M NaCl solution fed at a HRT of I h was preferred for the regeneration process, and more than 95% of adsorbed ammonium ions were recovered after using 7-8 bed volumes (BV) of the regenerating solution. The adsorption-regeneration time ratio was approximately 5:1. High concentration of potassium ions in the composting leachate competed with NH4+ ions for the exchange sites, resulting in a reduction in the efficiencies of ammonia removal and zeolite column regeneration. However, Zeolite still proved to have a great potential as a medium for ammonia removal in treating composting leachate.

Adsorption↗

PubMed2001

Treatment of greenhouse wastewater using constructed wetlands.

Five wetland designs, based on conventional surface flow (SF) and subsurface flow (SSF) approaches, were assessed for nitrogen and phosphorus removal from greenhouse wastewater. Results indicated none of the individual designs assessed was capable of providing the highest treatment effect for all nutrients of concern; however, the SF wetland emerged as the most appropriate design for the treatment of greenhouse wastewater. The highest mean phosphorus reduction of 65% was observed in the unplanted SF wetlands. Peak nitrate reductions of 54% were observed in the 15-cm deep SF wetlands and ammonia removal of 74% was achieved in the unplanted SF wetlands. Nitrate concentration in the greenhouse effluent can be reduced to acceptable levels for the protection of freshwater aquatic life (i.e., less then 40 ppm) using a loading rate of 1.65 g NO3-N/m2/day and a design water depth of 30 cm or greater. Based on available literature and the results of this research project, a multistage design, consisting of an unplanted pre-treatment basin followed by a 25 to 35 cm deep surface flow marsh with open water components, is recommended.

Agriculture↗

PubMed2001

Swine wastewater treatment using attached-growth and suspended-growth two stage sequencing batch reactors with real-time control.

Two two-stage sequencing batch reactors (TSSBR), one attached-growth and one suspended-growth, were operated under three levels of wastewater concentration (approximately 4,000, 2,000 and 500 TOC mg/L), respectively, to compare the pH and ORP (oxidation-reduction potential) patterns and system performance. In both TSSBR systems, the pH and ORP profiles varied with organic loading yet exhibited consistent patterns with distinctive features suitable for real-time control. For all runs at the three levels of influent, both systems achieved similar levels of treatment for BOD5, TOC and TSS of over 97.5, 93.4, and 97.3%, respectively. The attached-growth system out performed the suspended-growth system in achieving the same levels of treatment at much shorter aeration cycle times. The treatment efficiency for NO3(-)-N and PO4(-3) was greatly affected by the carbon content in the wastewater, and the best treatment was achieved during the TOC approximately 4,000 mg/L runs with final effluent at 4.0 and 21.3 mg/L, respectively.

Animals↗

PubMed2001

Ammonia removal from compost leachate using zeolite. II. A study using continuous flow packed columns.

Bench-scale packed zeolite columns were set up and operated to investigate the continuous removal of ammonium ions from compost leachate. The effects of hydraulic retention time (HRT), and particle size of the zeolite on the ammonia adsorption capacity were studied. For both the coarse particle and the powdered zeolite columns, higher ammonia removal efficiencies were achieved with longer HRT (i.e., lower influent flow rate) tests. At the same HRT, ammonia removal efficiencies from tests with powdered zeolite were generally 20% higher than tests with the coarse particle zeolite. A HRT of 6 hours was found appropriate for efficient ammonia removal, and an operating capacity of 1.31 mg N/g zeolite was obtained. Over 98% of the ammonia input from the influent was consistently removed for over 5 bed volumes (BV) of compost leachate flowing through the zeolite column. Zeolite proved to have a great potential as a medium for ammonia removal in treating composting leachate.

Adsorption↗

PubMed2000

Swine wastewater treatment in a two stage sequencing batch reactor using real-time control.

A laboratory scale two-stage sequencing batch reactor (TSSBR) was used to study the effectiveness of pH as a real-time control parameter in swine wastewater treatment. A Ringlace media was inserted into the A/O (Anoxic/Oxic) reactor for bacteria immobilization. The TSSBR was subjected to three levels of organic loading. The pH and ORP (Oxidation Reduction Potential) patterns obtained were consistent with distinct features, enabling the real-time control strategy to effectively set a flexible aeration time pending on influent concentration, hence resulting in flexible cycle time and HRT (Hydraulic Retention Time) for the system. The real-time process ensured a removal efficiency of over 99% and 95%, respectively, for ammonia and TOC (Total Organic Carbon). For NO3(-)-N and PO4(-3), the run with influent TOC = 4,000 mg/L yielded the most efficient removal of 61% and 95%, respectively. Test results suggest that pH can be a viable tool for on-line real-time control of a biological treatment process.

Agriculture↗

PubMed1999

Ultrafiltration tests for the reutilization of greenhouse wastewater.

A lab-scale experiment was performed using two different pore-size ultrafiltration membranes to investigate the removal efficiency of Tomato Mosaic Virus (ToMV), retainability of pollutant and nutrients, and flow characteristics. From the experiment, it may be concluded that ultrafiltration can be used effectively to eliminate ToMV. Tests with a 30K pore-size ultrafiltration membrane achieved 99% virus removal efficiency and a 5K membrane practically removed 100% of the virus in greenhouse wastewater. Nutrient analysis indicated that all the essential nutrients could be retained and re-utilized.

Membranes, Artificial↗