Environmental Technology

Pala, A. I.; Sponza, D. T.

doi: 10.1080/09593331708616434pmid: N/A

Pseudomonas sp. isolated from the activated sludge of a petrochemical industry treatment plant was harvested and used as an inoculum culture for biological treatment of petrochemical wastewaters. The objective was the comparison of biological treatment efficiencies between Pseudomonas sp. added activated sludge and normal activated sludge taken from the full scale treatment plant. Experiments were carried out both in batch and continuous operations using a laboratory scale activated sludge system. Monod kinetic was used to determine kinetic coefficients from the experimental data of continuous operations. The maximum COD utilization rate constant (k), saturation constant (Ks), microbial decay rate (kd), yield coefficient (Y) and maximum specific growth rate (μmax) were determined to be 0.95 1/day, 199 mgCOD/L, 0.10 1/day, 0.30 mgMLSS/mgCOD and 0.285 1/day for normal activated sludge, respectively. These coefficients were also determined for Pseudomonas sp. added activated sludge system as 2.75 1/day, 1035 mgCOD/L, 0.08 1/day, 0.32 mgMLSS/mgCOD and 0.88 1/day, respectively. Removal efficiencies of COD, TN and phenol for lower sludge ages were found higher for the Pseudomonas sp. added activated sludge system than that of the activated sludge system. Treatment efficiencies were found to be almost the same for both systems at high sludge ages.

Fdz-Polanco, F.; García, P.; Villaverde, S.

doi: 10.1080/09593331708616435pmid: N/A

The influence of adsorption and diffusion phenomena on the hydrodynamics of a submerged aerated filter was studied by using stimulus-response techniques. Two tracers, lithium chloride and blue-dextran, and two packing materials, sepiolite and puzzolane, were used. The RTD obtained were analyzed by using two theoretical models: the CSTR's (Completely Stirred Tank Reactor) in series model and the CSTR's with dead zone in series model. Experimental results confirmed that the influence of tracer adsorption on the liquid phase hydrodynamics is much smaller than the influence of its diffusion into the packing material. The use of different tracers brought about different results, which were interpreted according to their different diffusional behaviour. In all the experiments, the flow pattern approached to plug-flow. The results obtained from the RTD analysis with both models differed in less than 25% for the experiments done with lithium and sepiolite.

Sylvestre, S.; Lessard, P.; de la Noüe, J.

doi: 10.1080/09593330.1996.9618395pmid: N/A

The use of solar biotechnology could prove interesting for the removal of nutrients found in domestic wastewaters. A culture of cyanobacteria, P. bohneri, was grown on synthetic and wastewater media to study the removal performance of that process, and also to look at the dynamic behaviour of nitrogen and phosphate. Eight experiments were performed during the summer of 1993 using small batch reactors of 24 liters. Each experiment lasted between two and five days. Very good removal efficiencies were observed for all pollutants (N,P). Stripping of ammonia and precipitation of phosphate were found to be very important phenomena in the removal mechanisms, i.e. between 50 and 60% of the total removal.

De Laat, J.; Maouala-Makata, P.; Dore, M.

doi: 10.1080/09593330.1996.9618396pmid: N/A

Second-order rate constants for the reactions of molecular ozone and of hydroxyl radicals with some nitrogenous herbicides (phenyl-ureas and acetamides) have been measured in water at 20 °C using absolute and relative rate methods. Molecular ozone oxidation was carried out at acidic pH and in the presence of hydroxyl radical scavenger (tert-butanol). Hydroxyl radicals were generated from the aqueous decomposition of ozone by hydroxyde ions or by hydrogen peroxide. The order of kinetic rate constants for molecular ozone with the herbicides was found to be as follows: Isoproturon >> Chlortoluron > Diuron > Linuron ≈ Metolachlor ≈ Alachlor > Propachlor. Rate constants for the reactions of hydroxyl radicals with these herbicides were in the range of 4.3 109 – 5.2 109 l mol−1 s−1.

Beler-Baykal, B.; Oldenburg, M.; Sekoulov, I.

doi: 10.1080/09593331708616438pmid: N/A

The potential of ammonia removal through ion exchange with clinoptilolite was investigated under constant and variable loads. Clinoptilolite, by itself and in combination with a filter with biological activity was studied. Special attention was given to peak loads of ammonia. It has been demonstrated that ion exchange is a very promising tool for this purpose both for new plants to be designed and as upgrades in existing facilities.

Anderson, B. C.; Mavinic, D. S.; Oleszkiewicz, J. A.

doi: 10.1080/09593331708616439pmid: N/A

Pilot-scale research was conducted to quantify the effects of stabilizing combined wastewater sludges in side by side continuous aeration or cycled aeration (anoxic-aerobic) digestion operation at ambient temperatures. Varying ratios of raw primary sludge (RPS) and biological nutrient removal waste activated sludge (WAS) were digested at a number of fixed solids residence times (SRTs); digester operational efficiency was assessed on the basis of the amount and rate of volatile mass reduction, and the need and amount of required chemical for mixed liquor pH (MLpH) control. Volatile mass reduction efficiencies ranged from 30–55%, and depending on operational variables SRT, MLpH and WAS:RPS ratio, some of these values exceeded those from comparable WAS-only aerobic digesters. The WAS:RPS ratio had a significant effect on digester conditions and subsequent digestion behaviour and efficiency; the 60:40 WAS:RPS ratio reactors consistently outperformed the 80:20 ratio units. It is proposed that this was due to the RPS serving as external substrate to the digester biomass, allowing the organisms to maintain higher levels of activity, which resulted in better mass reduction at decreased SRT, and resistance to nitrification-induced MLpH decreases. It is suggested that some cost savings may be realised with this system, through possible digester downsizing and reduced chemical use, when operating in either configuration; however, site-specific examination is required to ensure operational compliance.

Khan, A. R.; Forster, C. F.

doi: 10.1080/09593331708616440pmid: N/A

Batch growth studies of Rhodococcus rubra on different substrates using 3.34% Czapek medium supplemented with 0.2% sodium propionate, nutrient broth, starch and ammonium sulphate respectively were investigated. A 3.34% Czapek medium supplemented with a range of concentrations (0–1%) of yeast extract were also investigated in order to maximise the biomass concentration and the surface activity related to the cells. Results suggest that both the biomass concentration and the amount of surface active materials which are produced during growth are dependent upon the quantity and the nature of the substrate. Results using starch as a nutrient source suggest the production of a potent biosurfactant whose surface activity can bring a marked decrease in surface tension. In addition, high growth does not necessarily impart greater surface activity to the cells. Growth inhibition studies using sodium laurate were carried out and the results suggest that R. rubra cannot be grown in a broth containing 50mg l−1 of this chemical. This was substantiated by pH measurements which were made during the work.

Canziani, R.; Pollice, A.; Ragazzi, M.

doi: 10.1080/09593331708616441pmid: N/A

Wastewater readily-biodegradable COD concentration is a critical parameter affecting biological nutrient removal efficiencies. Primary sludge hydrolysis has been recognized as a viable alternative to increase suspended solids degradability and provide biomasses with an extra load of available substrate. However, fermentation performance strongly depends on both feed sludge characteristics and process conditions. The aim of this paper is to evaluate the applicability of the process to real wastewater treatment plants operating under psychrophilic conditions. After a short review of previous research, some results of an experimental work are reported in order to explain some of the assumptions made. Then, a simple design procedure for primary fermentation systems is outlined and applied to a general situation. Results indicate that primary sludge hydrolysis at low temperatures (16–20°C) and recirculation of the separated liquid supernatant allows for little improvements in denitrification efficiencies. Maximum increase in nitrate reduction was estimated to be less than 3% as referred to the total influent nitrogen.

Yang, Y.; Zhang, D.

doi: 10.1080/09593331708616442pmid: N/A

A simple chemical - reduced method and then a modified rinse procedure were used to prepare finely divided silver powder without Raman background. When small amount of humic samples were diluted in a large excess of the silver powder and the mixtures were prepared as compacted discs, the Raman scattering signals of many humic samples could be reliably measured while the problems in the conventional Raman measurements of humic substances such as strong fluorescence and self - adsorption of the Raman scattered radiation were solved. The results revealed the graphite-like structures of the humic samples.

Garcia, R.; Maiz, I.; Millan, E.

doi: 10.1080/09593331708616443pmid: N/A

Superficial soil samples and grasses from different locations close to roads varying traffic flow and distance were analysed. The heavy elements: Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn were determined by atomic absorption spectrometry. The most notorious point was located near to A-8 highway; in that location Zn, Pb and Cu showed higher levels than critical soil concentrations. For Cd, Cu, Pb and Zn highly significant correlations between total contents in soils and DTPA extractable levels were found. Also, for these metals, significant correlations between metal levels in soils and contents in grass were obtained. Factor analysis was applied to heavy metal data and the association among Cd, Pb and Zn seem to have the same origin pollution source, motorized traffic.