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INTRODUCTION
India is a leading producer ,processor & exporter of
cashew in the world with annual production of
6,20,000 MT.
Cashew nut industries are mostly located in
peninsular india .
Listed as "Orange" Category Industries by various
SPCBs.
There are two commonly followed methods of
cashew nut processing
Roasting process & Cooking process
INDIAN SCENARIO
Roasting process is more popular in India, mostly in Kerala.
The roasting of cashew seeds is carried out in an inclined rotating open drum. Due to the high temperature of the drum, the CNSL in the cashew nut catches fire spontaneously and the nuts are roasted
The cashew nuts, in burning state, are discharged at the outlet of the drum and quenched immediately with spray of water to prevent further roasting.
These are small and medium scale industries ,man power intensive and with majority having no pollution abatement systems.
SOURCES OF WASTE WATER GENERATION
Initial washing of the raw cashew nuts.
Water used in the humidification step
Washing of flue gases from boiler
Washing of the equipment and the floor
CHARACTERSTICS OF EFFLUENT
The main liquid waste from the cashew nut processing are contaminated with CNSL (Cashew Nut Shell Liquid)
CNSL is a caustic, viscous liquid, which contains phenolics, mainly cardanol (60–65%).
CNSL is a liquid immiscible in water, because their components are highly hydrophobic
These phenolic compounds of high persistence, have acid characteristics, potentially carcinogenic and mutagenic
Despite being a by-product collected for marketing,
significant amount of CNSL is lost in the effluent. This is
due to the fact that extraction process is not yet fully
efficient.
The effluent generated has its color & varies from dark
brown and black.
Treatment is often difficult by conventional means, as
these compounds inhibit normal microbial populations of
functions, therefore, affecting the biological treatment
process (Rajkumar & Palanivelu, 2004).
COMPOSITION OF CNSL
CNSL is used for the production of paints, varnishes
,dyes, lubricants, disinfectants, insecticides.
EFFECTS ON WATER BODIES
Concentration above 1 mg/L can affect aquatic life.
The acute hazard to fish, aquatic invertebrates, and
aquatic plants is based on estimated toxicity values
for cardanol of 0.001 mg/L, 0.004 mg/L, and 0.010
mg/L, respectively.
Alkylphenols like cardanol have low solubility and
can contaminate the sediments of rivers (Unger &
Newman ,2003)
Source: U.S. EPA December, 2009 Hazard Characterization Document
WASTEWATER DISCHARGE
CHARACTERIZATION
Parameter mg/l
TSS - 1175 –2115
TDS - 2240 –4284
O&G - 1400 –2068
BOD - 5200 –10,424
COD - 14,790 –27,600
pH - 7.2-8.2
Source:CPCB
ECOTOXICOLOGICAL ANALYSIS OF CASHEW
NUT INDUSTRY EFFLUENTS
This study assessed the toxicity of this industrial effluent, specifically two of its major components, cardoland cardanol, using the brine shrimp (Artemia sp.) lethality assay
Survivors were counted after 24 and 48 hr of incubation of nauplii with samples.
The LC50 of cardol was 0.56 and 0.41 mg/L after 24 and 48 hr exposures, respectively, and of cardanol was 1.59 and 0.42 mg/L
Data from this study suggested that the cashew nut industry effluents are highly toxic to the environment in the Artemia sp. model and are potentially harmful to the environment
Martins et al , Pan-American Journal of Aquatic Sciences (2009),
WASTE WATER DISCHARGE STANDARDS
Parameter mg/l
BOD (270C and 3 days) - 30
Oil & Grease - 10
Suspended Solids - 100
Phenol - 1.0
pH - 6.5-8.5
Source :CPCB
EFFLUENT TREATMENT
Wastewater will be collected in a terminal collection
cum buffer tank.
Being a reclamation project, the entire wastewater
has to be collected in a central place and treated to
meet the good quality BOD norm of < 20 mg/l.
SBR (Sequential Batch Reactor) system is normally
recommended which will consist of:
Collection-cum-aeration-cum-settling tank
Sand Bed Filter system for decanted water filtration
Sludge drying bed for excess sludge
CPCB industrial document
AEROBIC REACTOR WITH FUNGAL
INOCULUMS (MARCUS ET AL)
Studies were conducted to assess the feasibility of an aerobic reactor inoculated with the fungus Aspergillus niger in reducing the toxicity of the effluent from the cashew processing industry
The study was on the effluent from WWTP of an industry that offers a treatment which basically consists of five steps: separation of coarse solids; equalization with aeration; screening; decantation and addition of hydrogen peroxide (aqueous 15 to 20% concentration) .
Reactor in this study used an aerobic fixed bed reactor and upward continuous flow inoculated with the fungus Aspergillusniger found in the waterbodies receiving effluent from indutry.
Once the nutrient solution started to be fed to the reactor the process of developing fungi were accelerated.
The analysis results show a significant positive correlation between both toxicity and phenolic content (correlation coefficient = 0.53), and between toxicity and COD (correlation coefficient = 0.60)
Fungal fixed bed reactor and upflow operated with a hydraulic retention time of 12 hours was highly efficient in reducing toxicity, total phenols and COD of effluent studied.
Filamentous fungi inoculated was dominant initially but at the end of the experiment yeast were capable of degrading the effluent satisfactorily.
The fact that yeast manage to survive in such a hostile effluent environment, degrading it and dominating all the space at the expense of filamentous fungi, highlights the great adaptive capacity of these organisms.
ENZYMATIC BIOREMEDIATION OF CNSL
CONTAMINATION(SOLY ET AL)
The aim was to find the utility of enzymes,
oxidoreductases and proteases for the
bioremediation of CNSL
The results show that peroxidase reduced the color
of the CNSL solution by polymerization and
precipitation.
Laccase, papain and fungal and bacterial protease
degraded the phenolic constituents.
The degradation was mainly at the double bonds of
the C15 hydrocarbon chain of the cardanol
BIOAUGMENTATION OF WASTEWATER FROM CASHEW
INDUSTRY (JERONIMO ET AL. 2012)
The study was aimed to assess the technical feasibility of the application of specific commercial strains of microorganisms (bioaugmentation) in the treatment of effluent coming from the processing of cashew nuts
The effluents collected were from the washing processes and humidification of cashew nuts.
Treatment tests were conducted with the addition of additive dose(about 25 mg / L).
The additive comprised of enzymes and viable bacteria (e.g. Pseudomonas aeruginosa LP602, Acinetobacter calcoaceticus)
Effectiveness of COD removal was measured on different operating conditions-anaerobic process ,aerobic process (without agitation) and the aerobic process with mechanical agitation.
The performance was monitored at the above three conditions ,observing change in pH, Acidity , COD, conductivity and turbidity over time.
It was concluded that the application of aerobic technique with agitation proved to be more viable with removal COD of the medium at levels greater than 80%.
TREATMENT ALTERNATIVES
The fungi used in biological reactors appear to be an alternative for the treatment of industrial effluents.
The potential of these microorganisms to degrade different types of substrates due to secretion of different enzymes, which act on the organic pollutant , making it more accessible to biodegradation (Rodrigues et al, 2006) .
In addition, the rapid reproduction and proliferation of these microorganisms and the ability to withstand possible variations of organic matter, oxygen, moisture and pH can be mentioned as indicators of viability employ them in biological reactors for the wastewater treatment (Rodrigues et al., 2006).
Such microorganisms in general, they promote degradation of aromatic compounds, through enzymatic systems P450 monooxygenase and lignolítico (Prenafeta boldu 2002).
CONCLUSION
Cashew nut industry waste water is rich in phenolic
contents.
Conventional biological treatments to these
effluents are not satisfactory as they contain high
amount of not easily biodegradable contents.
Bio remediation technologies can be used for
treatment of these type of waste water.
Reactors using Fungi is another alternative for
treatment.
REFERENCES Cashew nut processing: Sources of environmental pollution and standards-Atul mohod,
Sudhir jain and Powar A.G.
Bioaugmentation of wastewater from cashew industry- C. E. M. Jerônimo, H. G.
Fernandes , H. N. S. Meloe, J. F. Sousa
Removal of macronutrients from effluent of a cashew nut industry by using a batch
aerobic reactor with fungal inoculums- Marina Santos da Silva Lopes; Patrícia Celestino
Carvalho de Oliveira; Marcus Vinícius Freire Andrade
Comprehensive Industry Document – Cashew Seed Processing Industries,CPCB
Ecotoxicological analysis of wastewater of cashew chestnut processing industry before
and after treatment in aerobic reactor inoculated with fungi.- Marcionília Fernandes
Pimentel ,2010
Technical study for alternative treatment of oily wastewater arising from the cashew nut
industries- jerônimo, carlos enrique de medeiros
Organic matter removal efficiency of phenolic wastewater of cashew processing
industry by batch reactor with use of Aspergillus niger AN 400-Carla Bastos VIDAL
Degradation of Cashew Nut Shell Liquid by Pseudomonas sp Isolated from Soil- T.
Rajeswari, B. Padmapriya
Isolation, Identification and Methanogenesis of CNSL Degrading Bacteria and
Immobilized Bioremediation Techniques of CNSL and its Contaminated Water from
Cashew Industry- S. Sabna Prabha,
Enzymatic bioremediation of cashew nut shell liquid contamination-Soly Cheriyan,
Emilia T. Abraham