Efficacy Advanced Chemical Oxidation Process (AOP) for Sustainable Pretreatment of Mixed Dairy and Poultry Wastewaters in Nablus, Palestine

This study investigated the efficacy of advanced oxidation process (AOP) for the reduction of pollution loads in mixed agro-food industrial wastewaters (dairy and slaughterhouse) in Nablus city, Palestine. Bench scale Jar tests using an advanced oxidation process (AOP) were performed as a pretreatment stage. Initial results on direct applications of Fenton’s process on mixed agro-food wastewater (COD: 15400-18200 mg/l) were unsatisfactory. Hence, the performance of Fenton process was applied on three mixed wastewater samples with different pre-treatment trials: (A) coagulant (FeCl3.6H2O) addition, (B) settling (2h) and use of flocculent (lime Ca(OH)2) in sample (C). Preceded with lime, Fenton`s process (Sample C) was most effective in the removal of organic carbon and nitrogen (89% COD; 80% TKN). The removal efficiency in inorganic loads (91% TSS; 62% TS) were achieved under H2O2/COD (w/w ratio 2:1), H2O2/Fe +2 (w/w ratio 10:1) and acidic conditions (pH = 3). The adoption of AOP technology by agro-food industries could ensure compliance with municipal by-laws and acquire connection permits to sewerage networks.


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Wastewater effluents from dairies and poultry slaughterhouses, are organic-rich wastewater streams that require pretreatment prior connection to public sewer networks or illicitly discharged into receiving water bodies. Agro-food industrial wastewater have high biological oxygen demand (BOD) due to whey and blood contents. Wastewater originating from the various manufacturing processes have high contents of proteins, fats, and salts [1][2][3]. In addition, the remnants of the slaughterhouse due to the blood and the proudest wastewater from slaughtered animal [4]. Finding adequate treatment technologies for the pretreatment pertinent to pollution reduction and resources recovery is crucial.
In Palestine current water and environmental laws and water regulations, place national limits on industrial discharges and treated effluent from domestic and municipals dischargers, where Cabinet made Resolution Number (16) for the year 2013, "Bylaw on the House and Facilities' Connection System to the Public Sewage Network". The resolution for item (16) focus on the specification of industrial wastewater, where the COD limit is 2000 mg/l in order to allow to the industry to connect to the public sewage system [5]. These limits primarily aim at the reduction of organic and inorganic pollution loads, which promote eutrophication and impair public sewers [6], treatment facilities, environment, and public health. Consequently, municipal by-laws and effluent discharge standards dictate the level of wastewater treatment required and call for pretreatment of industrial effluents before connection to public sewer networks [5].
Limited access to water resources in Palestine, lack of financial resources and increasingly stringent local and regional regulations on municipal and industrial discharges, industries are under enormous pressures to reduce pollution loads by establishing advanced treatment and recycling of treated water in destined industrial production processes. All urban WWTPs in Palestine are designed to treat municipal wastewater but cannot adequately co-treat agrofood industrial effluents, which cause overloading in treatment processes and pollution of receiving natural watercourses. This study was conducted within the framework of INWA project, a Palestinian Dutch Cooperation (PADUCO) Program on Water. The study aimed at investigating the advanced oxidation process (AOP), a classical Fenton reaction, in the reduction of organic loads from mixed agro-food industrial wastewaters to enable safe connection to public sewer networks.

Materials and Methods
Samples of agro-food industrial wastewater have been collected from the dairy factory, and municipal slaughterhouse. The mixed of the previous samples have been tested to determine their physical and chemical properties. All samples prepared according to APHA (2005) [7].
The dairy samples contain sodium hydroxide (NaOH) and phosphoric acid (H3PO4) with concentrations (2.8-3%) which come from flushing, rinsing and disinfecting of the process tanks and piping, in addition to the whey which is separated in the cheese making process, while the samples from slaughterhouse contained diluted blood, and wastewater produced from washing the slaughtered animals (manure, and undigested feed). The results shown above revealed high concentrations in COD loads in the mixed agro-food industrial wastewater from dairy (whey) and blood from the slaughterhouse in Nablus city.

Analytical Methods
Physical parameters for raw and treated mixed agro-food wastewaters analyzed. The pH was measured using Metrohm-691, while the TSS and TS parameters according to the APHA Standard Methods [7]. Similarly, chemical parameters including Biological Oxygen Demand

Experimental Procedure
Classical Fenton's process has been applied with directly and with partially treatment.
Tests applied directly on the mixed of agro-food. Also applied partially for three samples: 1. Sample A: Coagulated by ferric chloride FeCl3.6H2O.
After partially treatment the supernatant, treatment by Fenton reagent applying two methods: without pH adjustment, and a second one with pH adjustment to get the desired results.

Directly Treatment By Fenton Reagent
The classical Fenton's process was applied for mixed agro-food industrial wastewater samples directly; with initial COD between was 15400-18200 mg/l. 2) Catalyst of Ferrous sulfate heptahydrate (FeSO4•7H2O; 5.2 mM Fe 2+ ) added to the sample before adding hydrogen peroxide. The molar ratio of H2O2/Fe 2+ w/w kept invariable at 10:1 and H2O2/ COD (w/w) kept constant at 2:1.

4) Terminate oxidation by the adjustment of samples' pH to 5-9 by adding lime
Ca(OH)2. Then, sample was kept for a period of 1 h to allow settling of solids and analyses of the supernatant followed.

Experimental Procedure of Partially Treatment samples
Sample (A) coagulation with ferric chloride FeCl3.6H2O: the sample of mixed raw dairy and slaughterhouse wastewater has been adjusted at room temperature (20±1 °C). Then in the jar 5 test 1.0 L volume of the sample coagulated by using ferric chloride (FeCl3.6H2O) aqueous solution with dosage 1g/L, the aqueous coagulant added in rapid mixing at 300 rpm for 3 min, then 30 min in slow mixing at 40 rpm. Followed by two hours of settling [8][9].
Sample (B) with sedimentation without coagulant: A one (1) liter of the raw wastewater (at room temperature) with initial pH and allowed settling for 2-4 h.
Sample (C) flocculation with Lime Ca(OH)2 : One litter of initial wastewater has been mixed with raw lime Ca(OH)2 by adding 1 g/l of and mixing it rapidly for creating flocculation [8], [10][11]. After partially treatment, that supernatant of samples had been gotten to complete treatment by Fenton's process as mentioned before once without pH adjustment and other with pH adjustment =3 and neutralization as following figures.

Direct Treatment by Fenton Reagent
Mixed samples of agro-food wastewater (poultry slaughterhouse and dairy) were treated directly by Fenton reagent. The results did not achieve the requirements (2000 mg COD/l) of Nablus connection by-law (CR 16/13) due low COD removal rates (45%) using H2O2/COD and H2O2/Fe +2 (w/w) at ratios of 2:1 and 10:1, respectively.

Three Treatment Trials Preceding Fenton Reaction
The first pre-treatment sample (A) is coagulation with FeCl3.6H2O. The treatment has been carried out to remove suspended compounds of wastewater through the formation of a solid precipitate (sludge) which will be treated [12].

Treatment by Fenton Reagent without pH Adjustment
At the first time, the pH was kept unadjusted and start the Fenton reaction for samples: Best result were for sample with flocculation, with a COD removal of 54% at pH of 11 and H2O2/COD (w/w) ratio of 2:1 and a ratio for H2O2/ Fe 2+ of 10:1. COD removal for samples coagulated (ferric chloride) and samples with sedimentation were almost equal (28% and 26% respectively) using same reaction conditions for flocculated samples, but at different pH values (8 and 10.5, respectively). Figure 5 depicts the performance of Fenton reaction in COD removal for the three treatment trials. Figure 5. COD removal (%) for three samples at initial pH without adjustment.
By leaving the samples without pH adjusting, the COD removal efficiency is not satisfactory in order to achieve CR 16/13.

Treatment with pH Adjustment and Neutralization
An acidic solution (HCL) has been used to modify the pH value from basic to acid media in order to make adequate conditions to start reaction. It is found that the degradation efficiency increased rapidly, organic removal was significantly higher in acidic conditions at pH 3 than under alkaline conditions. pH optimum for Fenton reaction is around 3 based on literature data to avoid precipitation of iron oxide-hydroxide which enhance the reaction [14]. This is crucial to produce hydroxyl radicals, responsible for the breakdown of organic matter and for oxidation reaction [13]. The ratio of H2O2/COD (w/w) was kept 2:1 and H2O2/ Fe 2+ 10:1.
The results of the experiments showed that the best sample in removal of organic load is the flocculation with lime Ca(OH)2 . It has been found that the removal rate for COD reached 70 % and for TSS and TS removal reached 65%, 47% respectively, and has been found that TKN reached 80% with the ratio of H2O2/COD (w/w) 2:1 and H2O2/Fe 2+ 10:1, and at the room temperature and within 1 hour. Samples coagulated with ferric chloride achieved COD removal of coagulated by is equal 52% and for TSS and TS removal reached 68% 48% ( Figure 6 and 7). Moreover, TKN reached 69% removal at the same ratios (Figure 8 and 9).
For the sedimentation sample, the removal rate for COD reached 33%. The value of COD removal is low, and not accepted so this sample has been excluded for other results. After treatment, all samples have been neutralized at pH=7.3.The performance of Fenton reaction in COD removal shown in Figure 6, for treating three samples. By adjusting the pH, value for the three samples, the COD removal efficiency satisfactory for the sample which pretreating by lime Ca(OH)2, in order to achieve CR 16/13. According to results of COD removal, Sample A and C recommended for further tests.

Effect of H2O2 and Catalyst Dosage on Treatment Efficacy
In Fenton reaction process H2O2 is the main source of hydroxyl radical •OH which produced under catalyst, and has a key role in reducing the organic load of wastewater. The optimal dosage of hydrogen peroxide was determined experimentally and by calculations.
Insufficient dosage or little of hydrogen peroxide H2O2 led to decrease in COD removal of the organic load regarding to insufficiency hydroxyl radical •OH. In contrast an increasing in dosage of H2O2 specially in treating wastewater with high COD value to increase the efficacy of COD removal, the excessive dosage of H2O2 will affect the microorganisms which used in removing contaminant, also an excessive in the concentration of H2O2 will result in self-disintegration into H2O and O2 [16]. Data obtained in this study are in compliance to what Shewa and Dagnew [17] reported. They underlined the role of AOP with coagulation and flocculation as a cost-competitive option for the pretreatment of industrial wastewaters. Advanced oxidation process is not a new technology, Peres et al. [18] listed other advanced technologies including electrochemical [19], and membrane-based processes, where AOP is increasingly applied, a competitive option for industrial wastewater treatment. Table 2 shows the summary of removal rates (as percentages) for the min physical and chemical parameters for the three different treatment trials. Trials were made in triplicats to determine the optimal dose for H2O2 reaching an optimal H2O2/COD ratio (w/w) of 2:1. production. The optimal FeSO4 dose tested has resulted in an optimal H2O2/Fe +2 of 10:1 ratio.

Conclusion
The paper addressed characterization and efficacy of AOP technology for mixed industrial effluents treatment to meet municipality by-law requirements for sewer connection. Based on the results analysis of this study, the following conclusions are elucidated: • A pre-treatment stage before Fenton process is necessary to reduce the pollution loads as per local national requirements for organic rich industrial polluters.
• Lime addition coupled with Fenton reaction enhanced the COD removal rates.
• Application of AOP could help reduced illicit industrial discharges and enable agrofood industries connect to public sewerage networks, thus complying with Nablus CR 16/13 sewer connection by-law.
• Scaling up the Fenton process from bench scale into pilot systems warrants further studies at small and large-scale agro-food industries.
The coagulation/flocculation was effective for the pre-treatment of agro-industrial wastewater, mainly for lowering the COD and TSS to levels, where further post-treatment stages including AOPs and/other biological processes are applied.

Acknowledgment
The Palestinian Dutch Program PADUCO2 on Water provided funding for this study.

Conflicts of Interest:
The authors declare no conflict of interest.