Feasibility of Combined Fenton & Coagulation Method for the Treatment of Pesticides Waste Water

Feasibility of Combined Fenton & Coagulation Method for the Treatment of Pesticides Waste Water

Amita P Upadhyay(1) & Dr.N.J Mistry(2)

PG Student in M Tech Environment(1) & Professor(2) in SVNIT,Surat

Abstract

The uses of Fentons reagent for the degradation of pesticides wastewater has been investigated. Optimization of process parameters lik e pH, dosages of H2O2 & FeSO4 ,Contact time(Aeration time) has been check ed pH, contact time & concentration of Fentons reagents are playing a k ey role in treatment process. At the first stage of the experiment different combination of the sets has been done with respect to FeSO4 & H2O2 to check the efficiency of COD & BOD removal. After getting optimum dosage of Fenton reagent(FeSO4+H2O2)with different contact time(Aeration hrs-2,3,4,) has been observed. At second stage, Coagulation will be given as pre-treatment to increase efficiency of Fenton & to reduce cost & amount of Fenton reagents. So throughout study wastewater treated with coagulants ( Al2SO4 +lime) with combination of Fenton process to give the maximum C OD & BOD removal efficiency from pesticides waste water sample.

Key words: Fenton reagent ,Pesticides effluent, COD- BOD, Re moval efficiency, Coagulation.

Industrial effluents from various industries like te xt ile, dyestuffs, Pesticides, paper and pulp, medic inal products, drugs, dying olive oil mill and metal industries etc. are the major contributors to water pollution as they create more subtle effects on behaviour, reproduction or eve even survival of biotic communit ies. Pesticides used in India are of diffe rent types such as orgonachloride, organophoshrous, urea, anilidesect. insecticides are of great significance in pest control & are increasingly in used. the pesticides & chemical industries are consider to generate wastewater containing toxic & non-biodegradable compounds that re main in the environment even after their waste have been subjected to conventional processing. Pesticides include a large a mount of organic matter that ma kes the

environment challenging .The appearance of to xic

,carcinogenic are difficult to degrade by biological method, So fo r the solution of this problem has involved Advanced oxidation process(AOP).

Among AOPs, the Fentons reagent (K. Barbusinski) has been efficiently used as a chemical process for wastewater treatment and pre-treat ment. The Fentons system consists of ferrous salts combined with hydrogen peroxide under acid ic conditions. Oxidat ion with o zone or hydrogen peroxide has been found to be an important alternative to chlorination, because the oxidation does not result in toxic chlo rinated organic compounds

The high COD concentration is found typically in pesticides effluent required special treatment. The presence of toxic substance would have an effect on ecosystem but also on conventional system. The application of coagulation-Fentons process for the treatment of pesticides wastewater has received considerable attention due to hid COD re moval efficiency & cost effectiveness. The effectiveness varies with nature of organic co mpound & properties of waste water. To improve effic iency of COD -BOD re moval, the uses of Fentons followed by coagulation process is helpful.

In 1894, che mists first discovered organic Fenton in (H2O2) and Fe2+ can be mixed solution consisting of the rapid oxidation, and to such a system known as the standard Fenton reagent can be that many of the known organic compounds such as carboxylic ac id, a lcohols, esters of inorganic o xidation, o xidized e ffect is very obvious . Fenton reagent was mixed by H2O2, Fe2+ gets a strong oxidant; in particular, apply to certain difficult to control, or biologica l to xic industrial wastewater.

The Fentons treatment has been widely applied in the treatment of non-biodegradable wastewater in fie ld of AOP. the e fficiency of Fentons depends on properties of wastewater, pH values,Fe+2 :H2O2 conc., &

reaction time (Aeration). Moreover, iron(Fe+2) is highly abundant & non toxic e le ment & hydrogen peroxide (H2O2) is easy to handle environmentally. this treatment have proved worthy in this treatment have proved worthy in this fie ld ,achieving good results in destruction of pollutants. the objectives of this study was to investigate the performance of Fentons reagents & couple applicat ion of coagulation plus Fenton.

Fenton's chemistry uses hydrogen peroxides (H2O2) and iron salts where the effectiveness of H2O2 is improved by iron through generation of highly reactive hydro xyl radicals.

Fe2+ +H2O2 Fe3+ + OH + OH 1.0

The hydroxyl radica l(OH ) is a powerful, che mica l oxidant, which acts very rapidly with organic compounds .

• OH+pollutantsmineralizationor(CO2+H2 O)1.2

According to reaction (1), Fe2+ is oxid ized to Fe3+ and then regenerated through the reduction of ferric ion by H2O2 , as shown in Eq. (1.2)

Fe3+ +H2O2 Fe2+ +HO2 + H+ 1.3

1.2.1 Factors affecting Fenton reagent

I] Effec t of Iron Concentr ati on.

In the absence of iron, there is no evidence of hydroxyl radica l formation when, for e xa mp le, H O is

to the transition of iron from a hydrated ferrous ion to a colloida l ferric species. In the latter form, iron catalytically decomposes the H2O2 into oxygen and water, without forming hydroxyl radica ls. The effect of pH on reaction effic iency is illustrated below.

Figure: 1 Effect of pH on Fentons Reagent.

The optima l pH occurs between pH 3 and pH 6. The drop in efficiency on the basic side is attributed to the transition of iron fro m a hydrated ferrous ion to a colloida l ferric species. In the latter form, iron catalytically decomposes the H2O2 into oxygen and water, without forming hydroxy l radicals.

IV] Effec t of Re action Ti me.

The time needed to complete a Fenton reaction will depend on the many variables discussed above, most notably catalyst dose and wastewater strength.

2 2 After getting optimu m dosage of Fenton

added to a phenolic wastewater (i.e ., no reduction in the level of phenol occurs). As the concentration of iron is increased, phenol removal accele rates until a point is reached where further addition of iron becomes ineffic ient. This feature (an optimal dose range for iron catalyst) is characteristic of Fentons Reagent, although the definition of the range varies according to wastewaters.

II] Effect of H2O2 Conce ntr ati on .

Because of the indiscriminate nature by which hydro xyl rad icals o xidize organic mate ria ls, it is important to profile the reaction in the laboratory for each waste to be treated. This is frequently seen when pretreating a comple x organic wastewater for toxic ity reduction. As the H2O2 dose is increased, a steady reduction in COD may occur with little or no change in toxicity until a threshold is attained, whereupon further addition of H2O2 results in a rapid decrease in wastewater toxic ity.

III] Effect of pH.

The optima l p H occurs between pH 3 and pH

6. The drop in e fficiency on the basic side is attributed

reagent(FeSO4+ H2O2)with different contact time(Aeration hrs -2,3,4,6) has been observed to check efficiency of COD & BOD re mova l.

1. At As the first stage of the experiment studies, Attempts were made to check the efficiency of Fentons process. Diffe rent combination of the sets has been done with respect to FeSO4 & H2O2 to check the efficiency of COD & BOD re mova l. After getting optimu m dosage of Fenton reagent(eSO4+ H2O2)with diffe rent contact time (Aeration hrs -2,3,4,6) has been observed to check effic iency of COD & BOD re moval.

   At second stage, Coagulation will be given as pre- treatment to increase efficiency of Fenton & to reduce cost & amount of Fenton reagents. So throughout study wastewater treated with coagulants ( Al2SO4 +lime) & (FeSO4 +lime ) with co mbination of Fenton process to give the ma ximu m COD & BOD re mova l effic iency fro m pesticides waste water sample. Th is will decrease the amount of Fentons reagent & increase efficiency of treatment .Thus, comb ine treat ment will a lso decrease

   treatment cost & bring down the limits of waste water effluent under the GPCB limits.

   1. Fenton Process.

      • 300 ml wastewater samp le was added in a flask, measure the pH.

      • The samples pH was adjusted to desired values (pH 3) using sulphuric acid.

      • The scheduled ferrous ions (Fe+2) dosage was achieved by adding necessary amount of solid FeSO4.7H2O.

      • A given volume of 35% (w/w) hydrogen peroxide (H2O2) solution was added to start up the Fentons reaction.

      • For vigorous & adequate mixing using Air pump with capacity (250 ml/hr) for diffe rent reaction time 2,3,4, hrs.

      • Subsequently, final pH was neutralized or adjusted to pH=7 with sodium hydroxide and is followed by sedimentation for 1 hour.

      • After sedimentation the supernatant was taken for analyzed for BOD-COD.

   2. Coagulation Process.

      Ta ke 300ml of samp le in beake r of 1litre size. Optimized dosage of Al2SO4 is added to fixed volume(300ml) of samp le. p H of sa mple is adjusted to 8-9 with use of lime. then place it in ja r test apparatus. Mixed it for 20mins,at 120rp m.Then the sample is standstill fo r 30mins to settle out flocs. After 30mins,withdrawn supernatant & filter it. The filtrate is checked for COD-BOD analysis to check the degradation efficiency by coagulation.

   3. Combined coagulation-Fentons process

      In this set of expe riment first of all coagulation process is carried out with optimized dosage of coagulation Alumin iu m sulphate (3.5g m/300ml ,pH:8- 9,rp m:120,time :20mins)with ja r test apparatus. Here also, batch experiments are carried out. Stand still 30min for settling of flocs. Withdrawn supernatant & filter it ,checked for COD-BOD ana lysis.

      After getting significant reduction of COD- BOD(55-66%) with coagulation process,In which ,pH of sample is alkaline so adjusted to acidic pH by

      sulphuric acid(98% conc.).Then Fenton experiment is carried out with optimized dosages of H2O2- FeSO4(1.8g m+18ml,2.5g m+20ml,3.5g m+22)

      respectively, at fixed p H 3 & d iffe r react ion time(2,3,4 hrs)air pu mp was attached for vigorous mixing.

   4. Characte ristics of Pesticide waste wate r.

      Waste water or raw effluent was collected from pesticides industry A situated at ankleshwar. waste water collected in 15liter container. The sa mple was immed iately acid ified at pH 2 & it is kept for the preservation into freezer.

      Para meters	Values
      pH	7.32
      COD	8700 ± 200
      BOD	3450 ± 100
      Sulphate	7.61 mg/l
      Ammonica l Nitrogen	6.5 mg/l
      Chloride	2300 mg/l
      TSS	736mg/l
      TDS	18,250 mg/l

      Table no : 1 Characteristics of Pesticide waste water

2. To observe optimu m concentration of hydrogen peroxide(H2O2) & Ferrous sulphate(FeSO4) for degradation or removal of COD & BOD e xperiments were conducted by varying dosage of hydrogen peroxide(H2O2) & ferrous sulfate at fixed pH & reaction time(2 hr)

   (FeSo4+ H2O2)	er	(mg/l)	(mg/l)	n
   1.5g m+1 2ml	COD	8700	6772	22.15
   	BOD	3450	2711	21.42%
   1.5g m+1 5ml	COD	8700	5233	39.85%
   	BOD	3450	2004	41.89%
   2.5g m+2 0ml	COD	8700	3934	54.78%
   	BOD	3450	1656	52.00%
   3.5g m+2 4ml	COD	8700	4497	51.70%
   	BOD	3450	1728.45	49.90%

   Dosage (FeSo4+H2 O2)	par amet er	Initi al conc. (mg/ l)	Final conc. (mg/l)	(% ) reducti on
   2.0g m+10m l	COD	8700	6936.3 9	20.70%
   	BOD	3450	2711.3 5	21.41%
   2.5g m+12m l	COD	8700	6090	37.00%
   	BOD	3450	2408	34.20%
   1.6g m+16m l	COD	8700	5007.7 2	42.06%
   	BOD	3450	1914	44.50%
   3.0g m+22m l	COD	8700	3674	57.77%
   	BOD	3450	1552	55.75%
   5g m + 25ml	COD	8700	3828	56.00%
   	BOD	3450	1621	53.15%

   Table no:2 pH=3, Reaction time=2hrs, Dosage=Vary

   Reduction(COD & BOD)

   60 COD & BOD Reduction

   50

   40

   30

   20

   10

   0

   COD

   BOD

   Dossage(FeSO4 +H2O2 )

   Graph no:1 Removal Efficiency of COD & BOD

   Table no:3 pH=3, Reaction time=2hrs, Dosage=Vary.

   Reduction(%) in COD & BOD

   60

   50

   40

   30

   20

   10

   0

   COD & BOD Reduction

   COD

   BOD

   Dosage (FeSO4+H2O2)

   Graph no:2 Removal Efficiency of COD & BOD

   Fro m previous two crude sets significant reduction observed with ,(p H=3 ,R.T=2hrs)

   1. COD(57.77% ) & BOD(55.75% ) with dosage 3gm FeSO4 + 22ml H2O2 .

   2. COD(51.23%) & BOD(50.59%) with dosage 1.75g m FeSO4 + 17.5ml H2O2.

   3. COD(54.78%) & BOD(52% ) with dosage 2.0g m FeSO4 + 20ml H2O2.

   Dosage

   par amet

   Initial conc.

   Final conc.

   (% ) reductio

   sAbove results indicate that good reduction is achieved with Fe+2:H2O2-1:10 rat io.& also indicate that degradation of COD-BOD increase with increase

   dosage of Fentons reagents.A further increase of the H2O2 & Fe+2 ratio actually decreases the extent of degradation of COD-BOD.

   Dosage (FeSO4+ H2O2	Reaction Time
   	Reduction in %
   	3hrs		4hrs
   	COD	BOD	COD	BOD
   1.8g m+ 18ml	48.38	51.32	57.42	57.9
   2.5g m+ 20ml	60.09	58.66	67.02	66.49
   3.5g m+ 22ml	57. 49	62.12	73.93	70

   Table no:4 pH=3, Reaction time=2,3,4hrs, Dosage=Vary.

   Reduction(%) in COD

   80

   70

   60

   50

   40

   30

   20

   10

   0

   COD Reduction

   3 hr

   4hr

   Dosage (FeSO4+H2O2)

   Graph no:3 Effect of reaction time on Removal Efficiency of COD.

   Dossage (FeSO4+ H2O2)	Para meters	pH
   		2	3	5	8
   		Reduction %
   1.8g m+ 18ml	COD	38.4	49.6	23.4	14.92
   	BOD	35.90	51.92	29.83	17.22
   2.5g m+ 20ml	COD	54	57.42	30.20	19.2
   	BOD	55.3	57.09	26.03	15.30
   3.5g m+ 22ml	COD	68.25	73.93	32.03	20.14
   	BOD	65.01	70	29.15	18.5

   Table no:5 pH=2,3,5,8 Reaction time=2 Dosage=Vary.

   80

   70

   60

   50

   40

   30

   20

   10

   0

   COD Reduction

   2 pH

   3pH 8pH

   Dosage (FeSO4+H2O2)

   Reduction(%) in COD

   Graph no:4 Effect of pH on Removal Efficiency of COD.

   Pesticides wastewater is subjected to chemica l coagulation process. coagulation process removes COD,BOD & solids around 50-60% fro m wastewater

   pH has been observed to be highly important factor for the Fentons process. Experiment de monstrated the effect if pH(2,3,5 & 8 ) on re moval e fficiency of COD & BOD. Hydrogen peroxide react very fast in acidic media to produced hydroxyl radica ls(.OH). pH in acidic rang(2-4) reduction with models substance achieved range from 50-70% & ma ximu m effic iency achieved with pH 3.

   .coagulation process is carried out to enhance re moval of model substances. Here coagulation is provided with jar test(20mins,120rp m & dosage 1g m,2g m,3.5g m,4.5g m).lime is provide to adjust pH.

   First coagulation is given before the Fentons process as pre-treatment by use coagulant Al2SO4 to increase or enhance the efficiency of Fentons process in re moval of model substance. here 50-62% reduction(COD-BOD) is achieved with coagulation process.

   Dosage (Al2SO4 +Li me )	par ame ter	Initial conc. (mg/l)	Final conc. (mg/l)	(% ) reducti on
   1g m+1. 5ml	COD	8700	3977.64	49.00
   	BOD	3450	1880.25	46.90
   2.0g m+ 1.5ml	COD	8700	3716.64	57.28
   	BOD	3450	1424.16	58.72
   3.5g m+ 1.5ml	COD	8700	3186.81	63.37
   	BOD	3450	1380	60.00
   4.5g m+ 1.5ml	COD	8700	3480	60.09
   	BOD	3450	1373	59.89

   time(2,3,4 hrs) to observe removal effic iency of coagulation + Fenton combined treat ment.

   .

   Table no:6 Effect of coagulation (Al2SO4

   Dossage (FeSO4 +H2O2)	Para- meters	Process	Reaction Time
   			2hr	3hr	4hr
   			Reduction %
   1.8 gm +18ml	COD	Fenton	44.38	48.90	57.71
   		Coag+Fent	72.48	75.00	79.50
   	BOD	Fenton	43.21	51.32	56.91
   		Coag+Fent	69.47	73.55	77.69
   2.5gm +20ml	COD	Fenton	54.00	60.09	67.92
   		Coag+Fent	85.03	87.16	87.92
   	BOD	Fenton	52	58.62	66.49
   		Coag+Fent	81.57	84.00	86.05
   3.5gm +22ml	COD	Fenton	57.00	63.43	73.77
   		Coag+Fent	88.50	89.02	90.40
   	BOD	Fenton	55.75	62.12	70
   		Coag+Fent	86.32	87.01	89.77

   +Lime).(pH=8-9,stirring time=20min,120rpm)

   COD

   BOD

   70 COD & BOD Reduction

   60

   50

   40

   30

   20

   10

   0

   Reduction(COD & BOD)

   1gm+1.5ml

   2.0gm+1.5ml

   3.5gm+1.5ml

   4.5gm+1.5ml

   Table no:7 Combined treatment of coagulation(3.5gm Al2SO4 + 1.5ml lime) + Fenton (Optimum dosage of FeSO4+H2O2=1.8gm+18ml ,2.5gm +20ml ,3.5gm

   +22ml).

   Dossage(FeSO4 +H2O2 )

   Graph no:5 Effect of Coagulation (Al2SO4) on Removal Efficiency of COD.

   After observing good reduction with coagulation

   process as pre-treatment in third stage of this study wastewater is treated first with coagulation (Al SO

It is evident from result & discussion that good reduction is achieved with Fe+2:H2O2-1:10 ratio. COD(57.77%) & BOD(55.75%) with dosage 2gm FeSO4 + 20ml H2O2 & also indicate that degradation of COD-BOD increase with increase dosage of

2 4 Fentons reagents. A further increase of the H2O2 &

+lime ) process & then treated effluent is subjected to Fenton s process. First of a ll wastewater is treated with optimu m coagulation(3.5g m Al2SO4 + 1.5ml lime ,pH:9-8 ,rp m:120 ,stirring time :20mins) & filtrate obtain from it subjected to Fenton process with optimu m dosage (FeSO4+H2O2=1.8g m+18ml

,2.5g m +20ml ,3.5g m +22ml) & different reaction

Fe+2 ratio actually decreases the extent of degradation of COD-BOD. He re increasing the dosage above 4.5g m FeSO4 & 24 ml H2O2 Re moval efficiency is decrease.

Reaction time varies between 2-4 hrs for which re moval effic iency vary between 49-73% . Fenton process is very sensitive to pH .it is not given good

results in neutral or alkaline media. It works at acidic pH range. In this study ,it gives ma x reduction in pH rang(2-) .

pretreatment with coagulation found to be effective treatment wh ich give around 30-60% BOD-COD re moval effic iency with Al2SO4 coagulant. Pretreat ment given with Fenton will reduce the quantity of Fenton reagents which affect cost factor at industrial scale. By co mb ine (coagulation +Fenton) treatment ma ximu m re moval effic iency achieved, than Fenton alone.

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