AbstractWastewater treatment has been a challenge throughout theworld in line to the variable influent characteristics and strict regulationsof effluents. In response to this problem, a reliable and cost effective processhas been developed. A coupled of coagulation -flocculation method has beenapplied for the treatment from different type of wastewater bearing with a highconcentrations of organic and hazardous pollutants. Wastewater will be treatedusing coagulation-flocculation to remove high concentration organic pollutantand heavy metals in wastewater. Inorganic coagulants are commonly used in theprocess due to its low cost and ease of use. However, the application constrainedwith low flocculating efficiency therefore organic polymeric flocculants isadded to increase the flocculate efficiency with low dosage of coagulant use. The effect of coagulant dosages and pH on thecoagulation-flocculation efficiency process was studied and conditions wereenhanced corresponding to the best removal of turbidity, total suspended solid(TSS), total dissolved solid (TDS), biological oxygen demand (BOD), and chemicaloxygen demand (COD). However, the effect of combined coagulation-flocculationtreatment with carbon nanomaterials is more efficient than the conventionalcoagulation-flocculation process.
Advanced science and technology introducedthe combined adsorption in the process by using carbon based nanomaterials.Carbon based nanomaterials is highly effective with great capacity to absorb awide range of contaminants, fast kinetic, and large specific surface area. Italso has lower production cost and accessibility compared to othernanomaterials. This paper gives an overview on coagulation-flocculation andcombined coagulation-adsorption with carbon nanomaterialsfor the treatment ofwastewater. Keywords: Wastewater,Coagulation, Flocculation, TSS, TDS, Turbidity, BOD, and COD, Removal, CarbonNanomaterials, Adsorption 1.0 IntroductionThe water supply isthe fundamental requirements for human life. Without water, life cannot besustained beyond a few days and the lack of access to adequate water suppliesleads to the spread of disease (Guy Howard et al, 2003).
The wastewatertreatment is involved in order to protect the quality of life and limited freshwaterresources. Discharging wastewater without treatment into surface water resourcecan affect aquatic life negatively (Fuat et al, 2011).Wastewater highlycomposed of suspended particles, dissolved organic and inorganic matter as wellas several biological organisms such as algae, bacteria and viruses. Thismaterial has to be removed since water quality will be deteriorated.
The veryimportant step in water and in wastewater treatment is the coagulation – flocculationwhich is considered as one of the most important and widely used treatmentprocesses due to its simplicity and effectiveness. (N.D Tzoupanos, 2008).Coagulation-flocculationis a chemical water treatment methods applied in various wastewaters prior tothe sedimentation and filtration techniques to enhance the ability of atreatment process in order to remove suspended particles from the wastewater.Mostsuspended solids in wastewater takes a negative charge and they consequentlyrepel each other. This repulsion prevents the particle from agglomeratingcausing them to remain in suspension. The process of coagulation-flocculationtakes place in different steps intended to overcome the forces stabilizing thesuspended particles and letting the particle collision and development offlocs, which can be settled and filtered out of the water.
This processtechnique is comparatively simple and cost effective as long as those chemicalsare highly available and the dosage is adapted to the water composition.In spite of the greatnumber of wastewater treatment heavy metal has become the most environmentalproblem now a days. Therefore employing adsorption process by using nanomaterialsinwastewater treatment has become the promising techniquein the recent yearsdueto the adsorption properties and efficiency. Carbon nanotubes (CNT’s) have been proveneffectively for removing heavy metals ions such as lead, chromium, copper andnickel from wastewater(Haijiao et al.
2016). 1.1. WastewaterCharacterization Wastewater is themixture of liquid and transported water wastes from communities in homes,commercial buildings, and industrial facilities, along with any groundwaterinfiltration and surface and storm water inflow that may enter the sewer system.Understanding the characteristics of wastewater is very important since thisunderstand the reaction and interactions with the inorganic and organiccharacteristics of compounds. The wastewater is also called sewage is mostlywater by mass (99%) and solids (0.1%) shown in Fig 1.0.
(Michael et al.)Thecontaminants in wastewater include the biodegradable organic compounds, suspendedsolids, inorganic compounds, nutrients, metals and pathogenic microorganism.Fig 1.0 Composition of DomesticWastewater 2.0 Coagulation-FlocculationMethod Treatmentfor surface water sources involves chemical and physical removal of particulatematter by coagulation, flocculation, sedimentation, and filtration processes,along with disinfection to inactivate any remaining pathogenic microorganisms. Coagulation-flocculationis known as conventional method for wastewater treatment where the cationicinorganic salts are used as coagulants and anionic polymers are used asflocculants as shown in Figure 2.0 (TorOve L, 2009). Coagulation destabilizesthe particle’s charges with the help of the coagulants.
The coagulants withcharges opposite to those of the suspended solids are added to the water toneutralize negative charges and form a jellylike mass to bridge particles as aresult forming a large mass enough to settle or trapped in the filter (JohnsonPD, et al. 2008). On the other hand, flocculation is a process of wherebystabilized particles, or particles formed as a consequence of destabilization,are induced to come together, make contact, and thereby form large(r)agglomerates (Bratby, 2006). The factors that influence the efficiency oftreatments are type and dosage of coagulant-flocculant, temperature, pH, mixingtime, speed and retention time.