Biomedical subjects

A P Annachhatre

Publications and source records attributed to A P Annachhatre.

10 recordsLinked to original sources

PubMed2005

Bioremediation of sediments from intensive aquaculture shrimp farms by using calcium peroxide as slow oxygen release agent.

A viable treatment procedure was developed in this research with calcium peroxide (CaO2) as a slow oxygen (O2) release agent for bioremediation of polluted sediments from intensive shrimp farms containing high organic carbon, nitrogen and phosphorus. Experiments with sediment treatment by CaO2 were carried out with, as well as without, biomass seeding at pH ranging from 6.5 to 8.5. The sediment treatment applying CaO2 without seeding yielded a BOD5, organic-C and organic-N removal up to 95%, 17.6% and 75%, respectively compared to the removal of 66%, 8.6% and 57%, respectively in the controlled treatment without CaO, addition. The investigations were also carried out with CaO2 dosage with biomass seeding at different food-to-microorganisms (F/M) ratio between 0.1 and 0.25. The BOD, organic-C and organic-N removal up to 92%, 17.6% and 73%, were achieved for a F/M ratio 0.1. The experimental results indicated complete organic-P removal within 5-7 days of treatment without seeding and within the initial 2 days of treatment with seeding. The present research revealed that, the application of CaO2 could enhance the degradation of organic-C, organic-N and organic-P during the treatment of polluted sediment.

Animals↗

PubMed2004

Anaerobic ponds treatment of starch wastewater: case study in Thailand.

Anaerobic ponds are particularly effective in treating high-strength wastewater containing biodegradable solids as they achieve the dual purpose of particulate settlement and organic removal. Performance of an anaerobic pond system for treatment of starch wastewater containing high organic carbon, biodegradable starch particulate matter and cyanide was assessed under tropical climate conditions. Approximately 5000 m3/d of wastewater from starch industry was treated in a series of anaerobic ponds with a total area of 7.39 ha followed by facultative ponds with an area of 29.11 ha. Overall COD and TSS removal of over 90% and CN removal of 51% was observed. Active biomass obtained from the anaerobic ponds sediments and bulk liquid layer exhibited specific methanogenic activity of 20.7 and 11.3 ml CH4/g VSS d, respectively. The cyanide degradability of sludge at initial cyanide concentration of 10 and 20 mg/l were determined to be 0.43 and 0.84 mg CN-/g VSS d, respectively. A separate settling column experiment with starch wastewater revealed that a settling time of approximately 120 min is sufficient to remove 90-95% of the influent TSS.

Anaerobiosis↗

PubMed2004

Nitrogen removal during leachate treatment: comparison of simple and sophisticated systems.

Membrane bioreactors (MBR) have become common in treating municipal wastewaters. Applied to leachates treatment MBR were also successful with pilot scale experiments and full-scale facilities as well. We succeeded previously in designing an efficient nitrification-denitrification process with an ethylene glycol byproduct as carbon source for denitrification. Moreover, an unexpectedly high inert COD removal efficiency was also observed in the full-scale MBR facility thereby making it possible to increase the operating time of the final GAC (Granulated Activated Carbon) adsorber. Since MBR are very sophisticated systems. Simpler and "lower" cost systems can also be considered. For example it is possible to nitrify leachates from sanitary landfill using a simple infiltration-percolation technique with a low energy cost. To validate previously published laboratory experiments, a semi industrial-scale pilot installation was installed at the Montzen landfill site (Belgium). The process is based on infiltration-percolation through a granular bed. This well known process was modified to increase the load, notably by changing the support medium, adding an electric fan that is run intermittently and maintaining temperatures greater than 15 degrees C. The new material is a type of granular calcium carbonate with a large specific surface area. These technical improvements enabled the system to nitrify up to 0.4 kg NH4+-N/m3 of reactor bed per day at a hydraulic load of 0.35 m.d(-1), with an ammonia removal rate in the range of 80 to 95%. Despite the high ammonia nitrogen inlet concentrations, this system exhibits remarkable nitrification efficiency. Moreover, these performances are achieved in a batch mode system without recirculation or dilution processes. If complete nitrification is needed, it can be obtained in a second in series of bioreactors. The system can be classified as a low cost process. An international patent is pending. Possible performances of those systems were compared with the usual methods for leachates treatment.

Ammonia↗

PubMed2004

Modeling response of nitrifying biofilm to inhibitory shock loads.

To study the response of nitrifying biofilm to inhibitory shock loads, a lab-scale nitrifying biofilm reactor was operated in ambient conditions. Shock loads of various concentrations of inhibitory compound were applied to the biofilm. Aniline was used as an inhibitory compound. The experimental results were utilized to develop a model for predicting the variation of effluent nitrate concentration from the biofilm reactor for given shock loads of aniline concentration and exposure time both in exposure as well as in recovery phase. Close agreement between model and experimental observation of bulk aniline concentration and effluent nitrate concentration was obtained which indicates the usefulness of the model to estimate bulk aniline concentration and to predict the response of inhibitory shock loads on nitrifying biofilm.

Aniline Compounds↗

PubMed2004

Nitrogen removal in a fluidized bed bioreactor by using mixed culture under oxygen-limited conditions.

Nitrogen removal involving nitrification and denitrification was investigated in a fluidized bed bioreactor by using mixed culture sludge under oxygen-limited conditions. Methane was used as a sole carbon source for denitrification. In this study, optimal nitrification and denitrification rates were examined by varying methane and oxygen gas dissolution flow rates, 90 ml/min, 400 ml/min and 650 ml/min, in each. Simultaneously nitrification and denitrification was achieved. The total nitrogen removal rate was 15-mg N/g VSS. d, 21-mg N/g VSS. d and 26.4-mg N/g VSS. d at gas dissolution flow rate 90 ml/min, 400 ml/min and 650 ml/min, respectively. No significant accumulation of nitrite was found in this experiment. Nitrogen removal rates depend on gas dissolution flow rates. DO concentration was at 0.5-2 mg/L.

Bioreactors↗

PubMed2001

Biological sulfide oxidation in a fluidized bed reactor.

Feasibility of a laboratory scale fluidized bed process for biological sulfide oxidation to elemental sulfur and the formation of well-settleable sulfur sludge is demonstrated. Sulfide oxidation strongly depends upon oxygen concentration, sulfide loading rate and upflow velocity. At reactor dissolved oxygen concentrations (DOr) higher than 0.1 mg l(-1), sulfate was the main product of sulfide oxidation Upon increasing the sulfide loading rate, the sulfate production rate decreased as sulfide oxidation to sulfur showed marked increase. Low formation of sulfate could mean that sulfide was inhibitory to sulfate producing bacteria or that conversion of sulfide to sulfur was more favorable than sulfate production. Sulfide conversions higher than 90% were obtained at sulfide loading rates of 0.13-1.6 kgS mr(-3) d(-1). At DOr less than 0.1 mg l(-1), sulfur was the major end product of the sulfide oxidation. Upflow velocity in the range of 16-26 m h(-1) and sulfide loading rate of 0.9-1.6 kgS mr(-3) d(-1) were necessary for generation of biogranules containing 65-76% of elemental sulfur. The elemental sulfur production of 76% was obtained at upflow velocity of 17 m h(-1) with sulfide loading rate up to 1.6 kgS mr(3)d(-1). Morphological examination of the biogranules showed elemental sulfur deposition in the sludge granule and outside the bacterial cells.

Biomass↗

PubMed1996

Biodegradation of chlorinated phenolic compounds.

Chlorophenolic compounds are generated from a number of industrial manufacturing processes including pulp and paper manufacture. These compounds are found to be toxic and recalcitrant and hence their discharge into the environment must be regulated. Slow and partial degradation of chlorophenols under aerobic and anaerobic natural environment has been observed. Aerobic biodegradation of chlorophenols proceeds through the formation of catechols while under anaerobic conditions, reductive dehalogenation is the preferred metabolic pathway. Number and position of chlorine substituents on the phenolic ring has influence on the rate and extent of biodegradation of chlorophenols. In engineered systems, acclimatization of biomass to chlorophenols markedly enhances the biodegradation ability by reducing the initial lag phase and by countering inhibition. Partial removal of chlorophenols between 40-60% is usually observed in aerobic and anaerobic processes. Removal can be enhanced by a combination of aerobic and anaerobic operations.

Journal Article↗

PubMed1992

Microbial attachment and growth in fixed-film reactors: process startup considerations.

Optimal steady-state performance of any biofilm reactor requires a fully developed and mature biofilm. During fixed-film reactor startup phase, biofilm is in process of development and accordingly, process performance is difficult to quantify. Environmental, cellular and surface factors greatly influence the process of biofilm formation during reactor startup. Improved knowledge of nutritional, toxicological and environmental requirements of wastewater degrading microorganisms has helped define optimal microbial growth conditions. In case of anaerobic fixed film reactors the startup is hindered by low microbial growth rates, strict environmental requirements and limited ability of methanogens to adhere and form fixed biofilms. These obstacles could be overcome by proper support media selection and formulation of appropriate inoculation procedures and startup strategies.

Journal Article↗

PubMedDate not supplied

Biological sulfate reduction using molasses as a carbon source.

The feasibility of using a laboratory-scale upflow anaerobic sludge blanket process for sulfate reduction with molasses as a carbon source was demonstrated. Competition between methane-producing bacteria (MPB) and sulfate-reducing bacteria (SRB) was influenced by the chemical oxygen demand-to-sulfur (COD:S) ratio in the feed. Sulfate removal greater than 80% could be achieved at COD:S greater than 10 when MPB predominated. Activity of MPB and SRB was inhibited at a dissolved sulfide concentration of approximately 200 mg/L. Competition between MPB and SRB was intense as the COD:S was reduced from 5 to 2. Further reduction in the COD:S to 0.7 led to the formation of sulfidogenic granules. The COD removal decreased to approximately 30% at a COD:S less than 2 because of accumulation of sulfurous precipitates and the nonbiodegradable portion of molasses in the sludge. Reduced gas production rates further imposed limitations on diffusion of the organic substrate into granules. Sulfidogenic process operation yielded sulfate removal as great as 70% at a COD:S of approximately 3.5.

Bacteria, Anaerobic↗

PubMedDate not supplied

Upflow anaerobic sludge blanket treatment of starch wastewater containing cyanide.

Treatment of tapioca starch wastewater containing cyanide using an upflow anaerobic sludge blanket (UASB) process was investigated. Sludge from an anaerobic lagoon treating tapioca starch wastewater was used as seed. Performance of the UASB reactor with influent cyanide concentrations up to 25 mg/L was assessed. The inhibitory effects of cyanide were temporary and reversible. The process required longer recovery period for higher cyanide dosage. For 25 mg/L of cyanide concentration in the feed, the reactor required 15 days for complete recovery. Process performance was sensitive to operating parameters such as upflow velocity, cyanide loading rate, and chemical oxygen demand (COD) loading rate. A maximum cyanide loading rate of 0.38 kg/m3 x d was achieved in the process at a COD loading rate of 50 kg COD/m3 x d. Experiments with tapioca starch wastewater containing up to 10 mg/L of cyanide yielded satisfactory cyanide removal of approximately 93 to 98% and gas productivity of 7.5 m3/m3 x d with a COD loading rate of 30 to 40 kg COD/m3 x d.

Bacteria, Anaerobic↗