Strategies to improve the efficiency of tertiary nitrifying trickling filters

2000 ◽  
Vol 41 (4-5) ◽  
pp. 477-485 ◽  
Author(s):  
T. Wilk
Keyword(s):  
Biofilm Reactor ◽  
Trickling Filter ◽  
Long Term Effects ◽  
Filter Model ◽  
Trickling Filters ◽  
Biofilm Model ◽  
In Series ◽  
Flow Through ◽  
Operating Strategies

The long term effects of the conditions for a biofilm reactor are governed by slow microbial processes, such as the growth and decay of the bacteria. Simulations of a trickling filter model based on a multi species dynamic biofilm model and data from an experiment, where an NTF had been alternatingly fed unnitrified and completely nitrified wastewater, agree fairly well. Two different operating strategies of NTFs are studied by simulation: periodically inversing the order of two NTFs in series and varying the flow through NTFs operating in parallel. The simulations indicate that both strategies have a potential of increasing the nitrifying capacity of filters operating at low ammonium load, provided the influent concentrations of organic matter are low. However, to what extent the capacity is increased depends on the specific death rate of the nitrifiers, which needs to be further studied.

Biological removal of algae in an integrated pond system

1995 ◽  
Vol 31 (12) ◽  
pp. 21-31 ◽  
Author(s):  
P. G. J. Meiring ◽  
R. A. Oellermann
Keyword(s):  
Adsorptive Capacity ◽  
Trickling Filter ◽  
Laboratory Findings ◽  
Oxidation Pond ◽  
Trickling Filters ◽  
Biological Removal ◽  
In Series ◽  
The Media ◽  
Oxidation Ponds ◽  
Dark Green

A system of oxidation ponds in series with a biological trickling filter is described. It was known that this arrangement was incapable of reducing effectively the levels of algae present in the pond liquid even though nitrification was effected because of autotrophic conditions prevailing in the trickling filters. This very low trophic level explained the lack of adsorptive capacity present. By shortcircuiting less than 10 percent of the effluent from a fully loaded primary facultative oxidation pond to the trickling filter, the autotrophuc nature or the film in the trickling filter was sufficiently shifted towards a heterotrophic state that had sufficient adsorptive capacity to retain the majority of the algae. It is concluded that the algae, although being absorbed, stay alive on the film and do not contribute significantly to the carbonaceous load on the trickling filter. Further more the algae, although secluded from all sunlight, actually partake in the purification process, producing an effluent which, unlike a normal humus tank effluent, is surprisingly sparkling clear. This significant observation appears to be in line with laboratory findings by others who, when they artificially immobilised certain species of algae and passed water over them, concluded that the algae retained the potential to remove certain compounds from the water. Conglomerates of biologically flocculated dark-green algae are scoured off the film (or sloughed off as part of the film) and, having been photosynthetically inactive for some days, tend not to float, but settle very rapidly. A very significantly aspect of this development is the great potential it has for practical application in developing countries. The algae sloughed off the media are easily thickened and available for ultimate recovery from the water phase without the addition of chemicals.

Dynamic simulation of a low loaded trickling filter for nitrification

1999 ◽  
Vol 39 (4) ◽  
pp. 163-168 ◽  
Author(s):  
K. Seggelke ◽  
F. Obenaus ◽  
K.-H. Rosenwinkel
Keyword(s):  
Dynamic Simulation ◽  
Weather Conditions ◽  
Full Scale ◽  
Trickling Filter ◽  
Examination Period ◽  
Trickling Filters ◽  
Biofilm Model ◽  
Measuring Campaign

For this report, an existing biofilm model was examined in regard to its suitability for the simulation of full scale trickling filter for nitrification. The system was calibrated using the results ascertained in a measuring campaign under dry weather conditions. The verification was done using the results of a second examination period which included spells of stormwater input. It was possible for all periods to satisfactorily illustrate the degradation performance of the simulated trickling filters in regard to dynamics and quantity.

Long-term effects of selected xenobiotica on freshwater green algae: development of a flow-through test system

1993 ◽  
Vol 134 ◽  
pp. 735-740 ◽  
Author(s):  
H. Schäfer ◽  
A. Wenzel ◽  
U. Fritsche ◽  
G. Röderer ◽  
W. Traunspurger
Keyword(s):  
Green Algae ◽  
Test System ◽  
Long Term Effects ◽  
Flow Through

scholarly journals Long-term effects of the antibacterial agent triclosan on marine periphyton communities

2014 ◽  
Author(s):  
Martin Eriksson ◽  
Henrik Johansson ◽  
Viktor Fihlman ◽  
Alexander Grehn ◽  
Kemal Sanli ◽  
...  
Keyword(s):  
Microbial Communities ◽  
Antibacterial Agent ◽  
Control Level ◽  
Pulse Amplitude ◽  
Long Term Effects ◽  
Carbon Utilization ◽  
Short Term ◽  
Flow Through ◽  
Community Tolerance

Triclosan (TCS) is a widely used antibacterial agent that has become a ubiquitous contaminant in freshwater, estuary and marine environments. Concerns for potential adverse effects of TCS have been described in several recent risk assessments. Effects on freshwater microbial communities have been quite well studied but studies addressing effects on marine microbial communities are scarce. Here we describe short- and long-term effects of TCS on marine periphyton (microbial biofilm) communities. Short-term effects on photosynthesis were estimated after 60 – 210 minutes exposure. Long-term effects on photosynthesis, chlorophyll fluorescence, pigment content, community tolerance and bacterial carbon utilization were studied after exposing periphyton for 17 days in flow-through microcosms to 0.316 - 10 000 nM TCS. Results from the short-term studies show that TCS is toxic to periphyton photosynthesis. EC50 values of 1080 and 3000 nM were estimated using 14CO2-incorporation and Pulse Amplitude Modulation (PAM), respectively. After long-term TCS exposure in flow-through microcosms photosynthesis estimated using PAM was, however, not inhibited by TCS concentrations up to 1000 nM, but instead increased with increasing TCS concentration. Similarly, the amount of photosynthetic pigments increased after an exposure of 31.6 nM TCS and higher; at 316 nM TCS the pigment amounts reached between 140 and 190% of the control level. Pollution-Induced Community Tolerance (PICT) was observed for algae and cyanobacteria at 100 nM TCS and higher. In spite of the widespread use of TCS as an antibacterial agent, the compound did not have any effects on bacterial carbon utilization after long-term exposure.

Effect of Upper arm Brachial Basilic and Prosthetic Forearm Arteriovenous Fistula on Left Ventricular Hypertrophy

2007 ◽  
Vol 8 (4) ◽  
pp. 296-301 ◽  
Author(s):  
X.H.A. Keuter ◽  
J.P. Kooman ◽  
J. Habets ◽  
F.M. Van Der Sande ◽  
A.G.H. Kessels ◽  
...  
Keyword(s):  
Left Ventricular Hypertrophy ◽  
Arteriovenous Fistula ◽  
Ventricular Hypertrophy ◽  
Relative Increase ◽  
Left Ventricular ◽  
Long Term Effects ◽  
Echocardiographic Examination ◽  
Flow Through

Background Creation of an arteriovenous fistula (AVF) may increase left ventricular hypertrophy in the hemodialysis population. Aim of this study was to compare the effects of a brachial-basilic (BB) AVF and the prosthetic brachial-antecubital forearm loop access (PTFE) on cardiac performance. Methods Patients were randomized to receive BB-AVF or prosthetic brachial-antecubital forearm loop access. Before and three months after AVF creation patients underwent an echocardiographic examination. Mann-Whitney U-test was used to compare relative increase between the measured cardiac parameters for the two groups. Results Twenty-seven patients participated in the study. The relative increase in left ventricular parameters was not significantly different between the two groups. Only left ventricular end-diastolic diameter tended to be of significance. Mean blood flow through the brachial artery was 1680±156 and 1450±221 mL/min three months after surgery for the PTFE and the BB-AVF group, respectively. Conclusion After three months of follow-up, changes in cardiac structure were comparable between patients with BB and PTFE AVFs. Also access flow was comparable at this time. In general, the effects of creation of a fistula on LV structure were limited. Longer follow up time may be needed to explore the long term effects of different vascular accesses on cardiac function.

scholarly journals Long-term effects of the antibacterial agent triclosan on marine periphyton communities

2014 ◽  
Author(s):  
Martin Eriksson ◽  
Henrik Johansson ◽  
Viktor Fihlman ◽  
Alexander Grehn ◽  
Kemal Sanli ◽  
...  
Keyword(s):  
Microbial Communities ◽  
Antibacterial Agent ◽  
Control Level ◽  
Pulse Amplitude ◽  
Long Term Effects ◽  
Carbon Utilization ◽  
Short Term ◽  
Flow Through ◽  
Community Tolerance

Triclosan (TCS) is a widely used antibacterial agent that has become a ubiquitous contaminant in freshwater, estuary and marine environments. Concerns for potential adverse effects of TCS have been described in several recent risk assessments. Effects on freshwater microbial communities have been quite well studied but studies addressing effects on marine microbial communities are scarce. Here we describe short- and long-term effects of TCS on marine periphyton (microbial biofilm) communities. Short-term effects on photosynthesis were estimated after 60 – 210 minutes exposure. Long-term effects on photosynthesis, chlorophyll fluorescence, pigment content, community tolerance and bacterial carbon utilization were studied after exposing periphyton for 17 days in flow-through microcosms to 0.316 - 10 000 nM TCS. Results from the short-term studies show that TCS is toxic to periphyton photosynthesis. EC50 values of 1080 and 3000 nM were estimated using 14CO2-incorporation and Pulse Amplitude Modulation (PAM), respectively. After long-term TCS exposure in flow-through microcosms photosynthesis estimated using PAM was, however, not inhibited by TCS concentrations up to 1000 nM, but instead increased with increasing TCS concentration. Similarly, the amount of photosynthetic pigments increased after an exposure of 31.6 nM TCS and higher; at 316 nM TCS the pigment amounts reached between 140 and 190% of the control level. Pollution-Induced Community Tolerance (PICT) was observed for algae and cyanobacteria at 100 nM TCS and higher. In spite of the widespread use of TCS as an antibacterial agent, the compound did not have any effects on bacterial carbon utilization after long-term exposure.

Validity of an Ecotoxicological Test System: Short-Term and Long-Term Effects of Arsenate on Marine Periphyton Communities in Laboratory Systems

1988 ◽  
Vol 45 (10) ◽  
pp. 1807-1815 ◽  
Author(s):  
Hans Blanck ◽  
Sten-Åke Wängberg
Keyword(s):  
Relevant Information ◽  
Test System ◽  
Physiological Parameter ◽  
Long Term Effects ◽  
Short Term ◽  
Ecotoxicological Test ◽  
Arsenate Stress ◽  
Flow Through ◽  
Chlorophyll A Content

Periphyton communities were established on glass substratum in the Gullmar Fjord (Sweden) and their sensitivity to arsenate was determined with short-term photosynthesis experiments. The study was done in May 1984 when phosphate levels were low. A 1-h exposure to arsenate gave IC20 (concentration required to inhibit photosynthesis by 20%) values of 0.4 μM. Communities established indoors in a flow-through aquaria system were substantially different from the fjord communities in terms of structure and biomass, although photosynthesis showed a similar sensitivity (IC20 = 0.6 μM). To explore the validity of this short-term ecotoxicological test system, we used a set of indoor, flow-through aquaria to study long-term effects (3 wk) on communities established under arsenate stress. Arsenate was added continuously at 0.1–10 μM above background levels (7 nM). Species composition as well as carbon, nitrogen, and chlorophyll a content of the communities were affected at 0.2–0.8 μM (IC20). This is in good agreement with the sensitivity of the short-term test. We conclude that inhibition of the physiological parameter photosynthesis is relevant information for the understanding of ecological events caused by arsenate stress in the periphyton communities. At least for effects of arsenate, the short-term metabolic test system can be used for valid predictions of gross changes in periphyton community structure and production. Comparison with arsenic levels in polluted coastal areas of Sweden lead to the conclusion that periphyton communities may be affected, particularly when phosphorus levels are low.

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