Water quality. Toxicity test for assessing the inhibition of nitrification of activated sludge microorganisms

2006 ◽  
Keyword(s):  
Water Quality ◽  
Activated Sludge ◽  
Toxicity Test ◽  
Inhibition Of Nitrification

Management of toxicity effects in a large wastewater treatment plant

1997 ◽  
Vol 36 (2-3) ◽  
pp. 1-8 ◽  
Author(s):  
P. Grau ◽  
B. P. Da-Rin
Keyword(s):  
Wastewater Treatment ◽  
Activated Sludge ◽  
Wastewater Treatment Plant ◽  
Treatment Plant ◽  
Severe Case ◽  
Treatment Efficiency ◽  
Filamentous Bulking ◽  
Biological Phenomena ◽  
Inhibition Of Nitrification ◽  
Toxicity Effects

An unusually severe case of toxicity accompanied by activated sludge filamentous bulking was observed at the wastewater treatment plant Sao Paulo-Barueri. Treatment efficiency of the plant, operated without major problems for more than five years before, was significantly hindered for almost six months. Occurrence of toxic shocks was confirmed partly directly but mostly indirectly by inhibition of nitrification and biological phenomena related to toxicity. Several measures adopted, including the recycled activated sludge chlorination, are described in the paper.

Changes in waste stabilisation pond performance resulting from the retrofit of activated sludge treatment upstream: part I – water quality issues

2005 ◽  
Vol 51 (12) ◽  
pp. 11-16 ◽  
Author(s):  
N.J. Cromar ◽  
D.G. Sweeney ◽  
M.J. O'Brien ◽  
H.J. Fallowfield
Keyword(s):  
Water Quality ◽  
Dissolved Oxygen ◽  
Activated Sludge ◽  
Algal Biomass ◽  
Inorganic Nitrogen ◽  
Treatment Plant ◽  
South Australia ◽  
N:P Ratio ◽  
Waste Stabilisation Ponds ◽  
Trickling Filters

This paper describes changes in effluent quality occurring before and after an upgrade to the Bolivar Wastewater Treatment Plant in South Australia. Trickling filters (TF) were replaced with an activated sludge (AS) plant, prior to tertiary treatment using waste stabilisation ponds (WSPs). The water quality in the WSPs following the upgrade was significantly improved. Reductions in total and soluble BOD, COD, TKN, suspended solids and organic nitrogen were recorded and the predominant form of inorganic nitrogen changed from NH4-N to NO2/NO3-N. The reduction in ammonium and potentially toxic free ammonia removed a control upon the growth of zooplankton, which may have contributed to decreases in algal biomass in the final ponds and consequently lower dissolved oxygen. Additionally, changes in inorganic nitrogen speciation contributed to a slightly elevated pH which reduced numbers of faecal coliforms in WSPs. The AS pretreated influent recorded significantly lower inorganic molar N:P ratio (10–4:1) compared to those fed with TF effluent (17–13:1). Algae within the WSPs may now be nitrogen limited, a condition which may favour the growth of nitrogen-fixing cyanobacteria. The decrease in algal biomass and in dissolved oxygen levels may enhance sedimentary denitrification, further driving the system towards nitrogen limitation.

An ecosystem modelling approach for deriving water quality criteria

2007 ◽  
Vol 56 (6) ◽  
pp. 19-27 ◽  
Author(s):  
F. De Laender ◽  
K.A.C. De Schamphelaere ◽  
C.R. Janssen ◽  
P.A. Vanrolleghem
Keyword(s):  
Water Quality ◽  
Toxicity Test ◽  
Quality Criteria ◽  
Single Species ◽  
Water Quality Criteria ◽  
Ecological Interactions ◽  
Ecosystem Modelling ◽  
Test Results ◽  
Data Set ◽  
Modelling Approach

Ecological effects of chemicals on ecosystems are the result of direct effects of the chemical, determined in single-species toxicity testing, and indirect effects due to ecological interactions between species. Current experimental methods to account for such interactions are expensive. Hence, mathematical models of ecosystems have been proposed as an alternative. The use of these models often requires extensive calibration, which hampers their use as a general tool in ecological effect assessments. Here we present a novel ecosystem modelling approach which assesses effects of chemicals on ecosystems by integrating single-species toxicity test results and ecological interactions, without the need for calibration on case-specific data. The methodology is validated by comparing predicted ecological effects of copper in a freshwater planktonic ecosystem with an experimental ecosystem data set. Two main effects reflected by this data set (a decrease of cladocerans and an increase of small phytoplankton) which were unpredictable from single-species toxicity test results alone, were predicted accurately by the developed model. Effects on populations which don't interact directly with other populations, were predicted equally well by single-species toxicity test results as by the ecosystem model. The small amount of required data and the high predictive capacity can make this ecosystem modelling approach an efficient tool in water quality criteria derivation for chemicals.

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