scholarly journals Impact of an Extreme Winter Storm Event on the Coagulation/Flocculation Processes in a Prototype Surface Water Treatment Plant: Causes and Mitigating Measures

Author(s):  
Fuguo Qiu ◽  
Huadong Lv ◽  
Xiao Zhao ◽  
Dongye Zhao

Climate change has often caused failure in water treatment operations. In this study, we report a real case study at a major surface water treatment plant in Alabama, USA. Following a severe winter storm, the effluent water turbidity surged to >15.00 Nephelometric Turbidity Units (NTU), far exceeding the 0.30 NTU standard. As a result, the plant operation had to be shut down for three days, causing millions of dollars of losses and affecting tens of thousands of people. Systematic jar tests were carried out with sediment samples from 22 upstream locations. The coagulation and settleability of sediment particles were tested under simulated storm weather conditions, i.e., low temperature (7 °C) and in the presence of various types and concentrations of natural organic matter (NOM) that was extracted from the local sediments. Experimental results proved that elevated NOM (6.14 mg·L−1 as Total Organic Carbon, TOC) in raw water was the root cause for the failure of the plant while the low temperature played a minor but significant role. Pre-oxidation with permanganate and/or elevated coagulant dosage were found effective to remove TOC in raw water and to prevent similar treatment failure. Moreover, we recommend that chemical dosages should be adjusted based on the TOC level in raw water, and a reference dosage of 0.29 kg-NaMnO4/kg-TOC and 19 kg- polyaluminum chloride (PACl) /kg-TOC would be appropriate to cope with future storm water impacts. To facilitate timely adjustment of the chemical dosages, the real time key water quality parameters should be monitored, such as turbidity, TOC, Ultraviolet (UV) absorbance, pH, and color. The findings can guide other treatment operators to deal with shock changes in the raw water quality resulting from severe weather or other operating conditions.

2014 ◽  
Vol 71 (4) ◽  
pp. 638-644 ◽  
Author(s):  
Alina Pruss

A technological investigation was carried out over a period of 2 years to evaluate surface water treatment technology. The study was performed in Poland, in three stages. From November 2011 to July 2012, for the first stage, flow tests with a capacity of 0.1–1.5 m3/h were performed simultaneously in three types of technical installations differing by coagulation modules. The outcome of the first stage was the choice of the technology for further investigation. The second stage was performed between September 2012 and March 2013 on a full-scale water treatment plant. Three large technical installations, operated in parallel, were analysed: coagulation with sludge flotation, micro-sand ballasted coagulation with sedimentation, coagulation with sedimentation and sludge recirculation. The capacity of the installations ranged from 10 to 40 m3/h. The third stage was also performed in a full-scale water treatment plant and was aimed at optimising the selected technology. This article presents the results of the second stage of the full-scale investigation. The critical treatment process, for the analysed water, was the coagulation in an acidic environment (6.5 < pH < 7.0) carried out in a system with rapid mixing, a flocculation chamber, preliminary separation of coagulation products, and removal of residual suspended solids through filtration.


2006 ◽  
Vol 54 (3) ◽  
pp. 23-28 ◽  
Author(s):  
J. Rapala ◽  
M. Niemelä ◽  
K.A. Berg ◽  
L. Lepistö ◽  
K. Lahti

The removal of cyanobacteria, hepatotoxins produced by them (microcystins), phytoplankton, heterotrophic bacteria and endotoxins were monitored at a surface water treatment plant with coagulation, clarification, sand filtration, ozonation, slow sand filtration and chlorination as the treatment process. Coagulation–sand filtration reduced microcystins by 1.2–2.4, and endotoxins by 0.72–2.0 log10 units. Ozonation effectively removed the residual microcystins. The treatment process reduced phytoplankton biomass by 2.2–4.6 and heterotrophic bacteria by 2.0–5.0 log10 units. In treated water, the concentration of microcystins never exceeded the WHO guide value (1 μg/L), but picoplankton and monad cells were often detected in high numbers. The heterotrophic bacterial isolates from the treated waters belonged to genera Sphingomonas, Pseudomonas, Bacillus, Herbaspirillum and Bosea.


2000 ◽  
Vol 41 (10-11) ◽  
pp. 43-49 ◽  
Author(s):  
C-N. Chang ◽  
A. Chao ◽  
F-S. Lee ◽  
F-F. Zing

The objective of this study is to investigate how the molecular weight distribution of the organic substances affects their treatment efficiencies and the reduction of disinfection by-products (DBPs) in the various unit operations of a full-scale water treatment plant. The results indicate that the membrane with a smaller molecular weight cut-off is more effective for removing the organic substances and its associated water quality parameters from the raw water. For example, using the membrane with a molecular weight cut-off of 0.5 K (500 daltons), the removal efficiency of DOC from the raw water sample can be as high as 88%. Removal efficiencies of other water quality parameters such as UV254 absorbance, THMFP and AOXFP are generally between 65–69%. When undergoing the various unit operations in the conventional water treatment plant, most organic substances are removed in the coagulation process followed by sedimentation.


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