Recent Applications of Coagulation, Flocculation and Ballast Flocculation in Treatment of Wastewater-A Review
Recent Applications of Coagulation, Flocculation and Ballast Flocculation in Treatment of Wastewater-A Review
Recent Applications of Coagulation, Flocculation and Ballast Flocculation in Treatment of Wastewater-A Review
MR. S. M. BHOSALE
Coordinator, Environment Science and Technology, Department of technology, Shivaji University Kolhapur,
Maharashtra, India
ABSTRACT
Coagulation-flocculation is a chemical water treatment technique basically used before
to sedimentation and filtration this enhances the ability of a treatment process to remove particles.
Coagulation and flocculation provide the water treatment process by virtue of which finely divided,
suspended and colloidal matter in the water is made to agglomerate and form flocs. This enables their
removal by sedimentation, dissolved air flotation or filtration. Ballasted flocculation is a high-rate, physical-
chemical clarification process, using rapid mixing flocculation and sedimentation for enhanced reduction of
suspended solids and biochemical oxygen demand (BOD).
The aim of this work was to review studies, on the wide and versatile range of feasible applications
employed in the purification of different types of wastewater. The coagulation-flocculation applications
discussed here were for different categories: leachate, textile wastewater; pulp and paper industry
wastewater; food industry wastewater; other types of industrial wastewater. In addition, this paper presents
an overview of the optimum process conditions and removal efficiencies (mostly high) achieved for the
technology applications discussed.
KEYWORDS: coagulation; flocculation ballast flocculation, textile, leachate, food industry, pulp and
paper, Wastewater
INTRODUCTION
A very important step in water and wastewater treatment is coagulation flocculation process, which is used
on large scale, because of its simplicity and cost-effectiveness., the coagulation-flocculation is usually
included, either as pre-treatment or as post-treatment step regardless of the nature of the treated sample and
the overall applied treatment scheme. The efficiency of coagulation-flocculation strongly affects the overall
treatment performance; hence, the increase of the efficiency of coagulation stage seems to be a key factor for
the improvement of the overall treatment efficiency. [6]
The purpose of coagulation and flocculation is to condition impurities, especially non-settleable solids and
colour, for removal from the water being treated. Coagulating chemical is the reason nonsettleable particles
clump together to form a floc. In the process of coagulation, chemicals are added which will initially cause
the colloidal particles to become destabilized and clump together. The particles gather together to form
larger particles in the flocculation process (see Figure1). When pieces of floc clump together, they may form
larger, heavier flocs which settle out and are removed as sludge. In other cases flocs are removed from the
water by flotation. (Water treatment manual, EPA)
Ballasted flocculation in conjunction with chemical coagulation rapidly enhances solid–liquid separation.
Ballasted flocculation can remove more than 85% of total suspended solids (TSS), 65% BOD, 80%–90% of
phosphorus, and 25%–35% of nitrogen on average. It is able to achieve good solids removal at a very high
surface overflow rate. Ballast material such as micro sand, a micro carrier, or chemically enhanced sludge is
effective in reducing coagulation-sedimentation time when coupled with chemical addition.
Practical review papers on Coagulation- Flocculation applications have been largely absent so far. To the
best of our knowledge, only a few authors have addressed the subject re- cently, therefore, there is a need for
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an update on recent applications of Coagulation Flocculation. The aim of this work was to accomplish this,
and based on the literature, to present an overview of practical optimum treatment times, current densities,
electricity consumption, and operating costs in a wide and versatile range of feasible applications of
coagulation Flocculation in water and waste- water treatment, studied mainly during the recent years.
LITERATURE REVIEW
FOOD PROCESSING INDUSTRY WASTEWATER
Vanerkar et al. carried out the treatment of Food Processing Industry Wastewater by a Coagulation/
Flocculation Process.
They collected and characterized food processing effluent composite samples. The samples were analysed
according to the procedures given in standard methods. The experiments were carried out using jar test
apparatus. Six beakers of 1 litre capacity were used in which one litre neutralized effluent was taken for
detail studies. Coagulant stock solutions were prepared and used for the complete set of each test. A study
on the effectiveness of lime alum, ferric chloride and ferrous sulphate individually and also with addition of
polyelectrolyte were carried out. Lime being the most cost effective chemical was tried first with food
processing wastewater. As the wastewater pH was around 4.2 the pH was adjusted to 7.0 before the start of
the experiments. A lime dose of 2.2 mg/L was required to neutralize the combined wastewater from initial
pH of 4.2. The neutralized wastewater was further subjected to chemical treatment (second stage) using
different conventional coagulants.
Results indicated that this wastewater is amenable to physicochemical treatment and can be applied either as
pretreatment technology or as a final polishing treatment. Lime dose of 200mg/ L resulted in optimum COD/
BOD reductions of 53.59% and 57.19% respectively. Amount of sludge development was only 25 ml/L at
this dose. Alum dosage resulted in very poor removals. This wastewater being highly protinous in nature
alum combines with protein and forms dense fine flocs which do not settle easily. At the alum doses
between 50 and 300mg/ L COD and BOD reductions varied between 16.81-29.97% and 22.81-38.81%
respectively. While removals incase of Ferrous Sulphate and Ferric chloride were slightly better between the
dosages of 50-175mg/L. But considering the cost of these two chemicals, lime was selected for further
studies using different polyelectrolytes. Lime dose of 200mg/ L was found to be optimum. This optimum
dose of Lime was kept constant and different anionic, cationic and nonionic polyelectrolytes were tried.
Results showed that Magnafloc E-207 was best among the selected polyelectrolytes. Results showed
0.3mg/L of Magnafloc E-207 in combination with 200mg/L of optimum dose of Lime were very effective
with COD, BOD and SS reductions of 67.61%, 71.01% and 81.53% respectively. While other two
polyelectrolytes depicted more or less similar results and reduction were comparatively lesser. Both
nonionic (i.e. Zetag 7650) and Cationic (i.e. Oxyfloc FL-11) showed 0.4 mg/L of polyelectrolyte as
optimum.
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The treatment using the natural coagulant, tannin, removed the largest amount of organic matter (expressed
in COD) for the characterization of the effluent considering BOD5, total solids, and metals, there was a
decrease in these parameters with both coagulants, but tannin had the best results
FLUORIDE-CONTAINING WASTEWATER
Wang et al. performed a Pilot-scale fluoride-containing wastewater treatment by the ballasted flocculation
process. A pilot-scale ballasted flocculation system was used to remove fluoride from one type of industrial
wastewater. The system included the formation of calcium fluoride (CaF2) using calcium hydroxide
followed by coagulation sedimentation. Calcium fluoride was recycled as nuclei for enhancing
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CaF2precipitation and as a ballasting agent for improving fluoride removal and flocculation efficiency.
Factors affecting fluoride and turbidity removal efficiencies, including pH in the CaF2-reacting tank and
coagulation-mixing tank, sludge recycling ratio, and dosages of FeCl3 and polyacrylamide (PAM), were
investigated in the pilot-scale system. The recycled CaF2precipitates improved CaF2 formation kinetics,
enhanced fluoride removal and flocculation performance. Under the optimized condition, the ballast
flocculation process reduced fluoride concentration from 288.9 to 10.67 mg/L and the turbidity from 129.6
NTU to below 2.5 NTU.
REFERENCE
1) A. P. Vanerkar., satyanarayan S, satyanarayan S , “Treatment of Food Processing Industry Wastewater
by a Coagulation/ Flocculation Process”, International Journal of Chemical and Physical Sciences Vol.
2, March 2013
2) Couto Junior O.M,, Dornelas Barros M. A. S. and Curvelo Pereira N, “Study on coagulation and
flocculation for treating effluents of textile industry”,Acta Scientiarum. Technology v. 35, n. 1, Jan.-
Mar., 2013 ,p. 83-88.
3) Rui L.M. , Daud Z.B, “ Efficiency of the coagulation-flocculation for the Leachate
treatment”,International Journal of Sustainable Development ,02:10 ,2011
4) Kumar P, Tow Teng T, Chand S, and. Wasewar K L, “ Treatment of Paper and Pulp Mill Effluent by
Coagulation” World Academy of Science, Engineering and Technology, 56, 2011
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ISSN: 2394-3696
VOLUME 4, ISSUE 3, Mar.-2017
5) Water treatment manual,EPA,2002
8) Wang B.Y, Chen . L, Zhu J, Shen J. M, and Ying Han, “Pilot-scale fluoride-containing wastewater
treatment by the ballasted flocculation process”, 68 (1) ; July 2013, 134-143
9) Kumar S, . Ghosh N C & Kazmi A. A., “ Ballasted sand flocculation for water, wastewater and CSO
treatment”, Environmental Technology Reviews, Volume 5, (1),2016
10) http://wastewaterinfo.asia/sites/default/files/tech-sheets/ballasted-flocculation.
11) http://www.aggnet.com/files/aggnet/attachments/articles/sandballasted_flocculation_technology
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