Efficiency of Moringa oleifera Seeds for Treatment of Laundry Wastewater

Laundry wastewater has simple characteristics in which the detergents compounds are the main constitutes. But these compounds have adverse effects on the aquatic organisms in the natural water bodies which received these wastes without treatment. Few studies were conducted on these wastes because it represent a small part of the total wastewater generated from different human activities. Moreover, the coagulation process for laundry wastewater might be effective to remove of detergents compounds. Therefore, in the present study, the efficiency of coagulation process by using chemical (ferrous sulphate) and natural coagulants (Moringa oleifera seeds) were investigated. The raw laundry wastewater samples were collected from laundromat located at Taman Universiti, Parit Raja. The characteristics of these wastes were determined and then the wastewater was subjected for the treatment process consisted of three units including aeration, coagulation and sedimentation process. The chemical and natural coagulants were used with four dosage (30, 60, 90 and 120 mg L) and the coagulation process was carried out at room temperature (25±2oC) for one hour. The results revealed that the laundry wastewater have high concentrations of turbidity (57.8-68.1 NTU) and Chemical Oxygen Demand (COD) (423-450 mg L) with pH value between 7.96 and 8.37. M. oleifera seeds exhibited high efficiency for removal of turbidity (83.63%) with 120 mg L of dosage, while 30 mg L of FeSO4 was the best for removal of COD (54.18%). However, both parameters still more than Standard B for wastewater disposal suggesting the need to increase the period of coagulation process with M. oleifera seeds or to subject of the treated effluents for a secondary coagulation process with natural coagulant products to improve the characteristics of laundry wastewater without a secondary products as that generated with the chemical coagulants.


Introduction
Detergent compounds are classes of the organic micro-pollutants (OMPs) in the laundry wastewater. The disposal of these compounds into the natural water bodies lead to aesthetic losses due to the foam which can also cause adverse effects on ecosystems and biodiversity [1,2]. Detergents compounds in the laundry wastewater are biodegradable compounds and they have a short persistence time in the environment. Nevertheless, the main hazard for these compounds are associated with their concentrations which might be very active and poisonous directly for the organisms within a short exposure time. The indirect effect of the detergent for aquatic life lies by lowering the surface tension of the water. Besides, the chemical composition of the laundry wastewater such as high chemical oxygen demand (COD) and total suspension solids (TSS) as well as pH might change the natural water characteristics and induce the occurrence eutrophication phenomenon. Therefore, these parameters have to be reduced in the laundry wastewater to the minimum concentrations. Among several technologies used for the treatment and reduction of organic compounds in the wastewater, the coagulation process represent the most potent technique for improving the characteristics of wastewater before the disposal into the environment. The coagulants substances used might be chemicals such as ferrous sulphate or natural such as Moringa oleifera. Nonetheless, natural coagulant have more advantages than chemical substances in term of toxicity and efficiency as well as the cost. The toxicity of chemical coagulants have reported in the literature, the correlation between the availability of ferrous sulphate (above 200 mg L -1 ) in the treated water and Alzheimer's and neuro-degenerative diseases has revealed by Bhatia et al. [3].
Moringa oleifera is known as a tropical plant with high contents of oil and water soluble molecules in their seeds [4]. M. oleifera seeds are used in the coagulation process due to the biodegradable characterize of their compounds. One advantages more of M. oleifera is the biological activity against bacteria which has demonstrated by the authors. M. oleifera has the potential to reduce cloudiness, clay and bacterial content of water in comparison to aluminium salts. Therefore, it represent an alternative and future technology for the wastewater treatment. Two process included absorption and neutralization of the colloidal charges are explained the mechanism of coagulation with M. oleifera. M. oleifera is non-toxic and biodegradable substrates, eco-friendly and unlike alum, has no effect on the pH and conductivity of the treated wastewater. Moreover, less amounts of sludge are generated when M. oleifera are used in the coagulation of wastewater in comparison to alum [5].
M. oleifera seeds extracts has exhibited an efficiency in the reduction of surfactant such as sodium lauryl sulphate fr om aqueous solutions, where 80% of the reduction has recorded [1]. It has been reduced TSS by 92%, total coliform by 89.6% and faecal coliform by 98.1% with 10 mL L -1 (v/v) of seeds concentrations [6]. However, the maximum reduction recorded for BOD and COD were 32 and 48% respectively. M. oleifera seeds have used for treatment different types of wastewater such as tapioca starch wastewater. Suhartini et al.
[7] used a system consisted of two-stage clarifier tanks filled with sand or coconut fiber and M. oleifera seeds. The system occurred high reduction of BOD, COD and TSS to meet the Indonesian standards limits of tapioca starch wastewater discharge. Laundry wastewater has a different composition to the domestic and agriculture wastewater. These differences lies the quality of the chemical characteristics rather than their quantity. Therefore, the potential of natural coagulant for the treatment of these wastes need to be investigated in order to give an evaluation for their role in the reduction of physical and chemical parameters in these wastes before the final disposal into the environment and this is the focus of the current work.
This study aimed to examine the efficiency of M. oleifera seeds as coagulant of laundry wastewater in comparison to the commercial coagulant such as ferrous sulphate. The potential of M. oleifera seeds in improving the quality of laundry wastewater was evaluated based on the reduction of COD, TSS, turbidity and pH which represent the main parameters of the laundry wastewater.

Study area and sampling
The laundry wastewater samples (5 L) were collected from laundromat located at Taman Universiti, Parit Raja (Latitude 1°51'3.12"N and longitude 103° 4'29.63"E). The laundromat was selected because it's a self-service laundromat where different types of detergents with different dosages are used and thus represent a good model to test the efficiency of natural coagulants. The samples were collected from discharge point (Fig. 1) in a plastic bottle (5 L) and then transported into the laboratory in ice box and subjected for the chemical and physical tests within two hours to prevent the degradation of detergents compounds. The characteristics of laundry wastewater including pH, turbidity, COD and TSS were determined according to APHA [8].

Preparation of M. oleifera seeds and ferrous sulphate
M. oleifera seeds were obtained from a local market at Parit Raja. The seeds were dried in order to improve level of polyelectrolyte presented in the kernels [9]. Thereafter, they were grounded into fine particles less than 0.20 mm of size and dried again at 100˚C for 24 hrs [10]. The dried seeds were milled into a fine powder by using domestic blender and then passed through 50-mesh sieve according to coagulant-method [3]. Ferrous sulphate (FeSO 4. 7H 2 O) salts (CAS: 7782-63-0, Fisher Scientific) was supplied from Tai`an Ming Chen Chemical Import and Export Co. Ltd, China.

Coagulation studies
The raw laundry wastewater were treated by using a treatment system consisted of three units included aeration, coagulation and sedimentation tank. The aeration process was carried out in order to remove carbon dioxide and oxidize soluble iron and manganese as well as to reduce hydrogen sulphide and ammonia. The coagulation process were performed with four concentrations of M. oleifera seeds and ferrous sulphate in order to determine the optimal concentrations required to achieve high removal percentage of the main parameters of laundry wastewater. The sedimentation tank was used to separation solid materials resulted from the coagulation process and clarified wastewater.
A fixed volume of (1 L) of laundry wastewater sample was stored in the aeration tank (25×17×18 cm) at room temperature (25±2 ºC) for 30 min. The wastewater was pumped into the coagulation tank using a water pump (Shanda), 120V. The coagulation tank made up of High-density polyethylene (HDPE) transparent bottle (14 cm×20 cm×14 cm) and Direct Current motor (DC Geared Motor, DC12V) with 1.1 watt, 103 rpm, 410 mA, 127.4 mN and 8 mm of shaft diameter [10]. Four concentrations [30, 60, 90 and 120 mg L -1 (w/v)] of M. oleifera seeds and ferrous sulphate were investigated separately. The wastewater sample was mixed with each concentration for one hour. At the end of the coagulation process, the wastewater was pumped slowly into sedimentation tank to settle for one hour. The supernatant generated from the sedimentation tank was used to determine pH, turbidity, COD and TSS according to APHA [8]. The control samples were conducted without chemical or natural coagulant. The removal efficiency was calculated according to the following equation; (1) where, is the initial parameter concentration (mg L -1 ), is the remaining parameter concentration (mg L -1 )

Results and discussions
The characteristics of laundry wastewater demonstrated that these wastes have high concentrations of COD (423-450 mg L -1 ) and turbidity (57.8-68.1 NTU) more than the standards limits recommended by Environmental Quality Act, 1974 (sewage and Industrial effluents, Regulation 2009). These standards are used for sewage and industrial wastewater, but it can be used for discharging laundry wastewater due to absence a specific regulation of these wastes. The high concentrations of COD might be due to the presence of detergents compounds, which lead to increase of chemical reaction level between organic substances. Laundry wastewater has high impurities due to the presence of sand and particles, oil and grease, surfactants, detergent and phosphates [11]. Despite, TSS and pH values were within the standards range, pH of these waste was more than pH 7.5, which might be related to the presence detergents compounds that include wide range of amphoteric, anionic and cationic compounds. Laundry water contains detectable concentrations of TSS, salts, nutrients, organic matter and pathogens raised from the clothes, laundry detergents and fabric softener residues [12]. Moreover, the detergents are the most abundant organic chemicals in these wastes [13]. Therefore, removal of these compounds is required before the discharge into the environment.
The efficiency of chemical and natural coagulant in the removal of TSS is presented in Fig. 2 a. TSS was within the standard limits of wastewater disposal regulated by Environmental Quality Act, 1974 (sewage and Industrial effluents, Regulation 2009). Moreover, M. oleifera seeds and ferrous sulphate exhibited an efficiency to reduce it by 73 and 78% at 90 and 120 mg L -1 of both coagulants respectively. It has revealed that M. oleifera seeds contain significant quantities of proteins with high molecular weight and water soluble protein, which carries a positive charge to the solution. These flocculating protein works as a clarifying agent of turbid water [4].
M. oleifera seeds and ferrous sulphate have recorded a significant reduction in the turbidity in comparison to the control (without coagulant) (Fig. 2 b). The maximum removal was noted with the high concentrations (120 mg L -1 ) of both coagulant.
However, M. oleifera seeds exhibited high efficiency in the turbidity removal than ferrous sulphate (83.63 vs. 59.02%). The efficiency of M. oleifera seeds in removal of turbidity might be related to the presence of water soluble cationic proteins which indicate for electronic charge and enhance coagulation and flocculation [14]. In contrast, FeSO 4 exhibited more efficiency in the removal of COD, the reduction was 54.18% with 30 mg L -1 for FeSO 4 , and 42.72% at 90 mg L -1 of M. oleifera (Fig. 2 c). These findings might be due to the nature of chemical reaction between FeSO 4 and organic constitutes in the wastewater which might occur more than that between M. oleifera components and the organic compounds. However, it has to mention that the reduction of COD with the addition of FeSO 4 take place due to the chelating process that bind to the organic matter with FeSO 4 . This process relied on the equilibrium between the substrates during the coagulation process. The high concentrations of FeSO 4 has decreased the removal; percentage of COD, due to the decreases in the affinity of organic compounds to adsorb of Fe ions. Besides, coagulation process with chemical chelating agents is accomplished with the generation of sludge. On the other hand, the efficiency M. oleifera seeds in the reduction of COD take place by the degradation of organic matter by using their compounds which have the degradation potential. The high ability of M. oleifera to degrade the organic compounds relate to the presence of protein in the M. oleifera. The binding of proteins to the organic compounds facility their consumption by the microorganism as carbon sources by using hydrolyses enzymes. But the degradation process need more time to cause a significant reduction in COD. In the present study the coagulation process was conducted for one hour which might be sufficient for the chelating process but not for the degradation process. It has demonstrated that even with high concentrations of M. oleifera seeds the reduction in COD might still limited [15]. Nonetheless, it can be indicated that the M. oleifera still better than FeSO 4 for reducing COD, because less sludge is produced with the natural coagulants as revealed by previous studies in literature [16] and the produced sludge is a degradable substances and has no toxicity characteristics. The absence of toxicity of produced sludge related to the nature of M. oleifera seeds which have no toxicity and they are used for the medical applications.
In all case, the results recorded here indicated that the final concentrations of COD and turbidity still more than the standard A and B required for the disposal of wastewater (Table 1). These findings indicate that the treatment system has to be conducted for more than one hour rather than to increase the concentrations of coagulants. This is because the increasing in these concentrations correlated with the reduction in pH value the minimum pH value recorded was pH 5.77 with 120 mg L -1 of both M. oleifera and FeSO 4 , this value is most close to the minimum pH required by Standard B (pH 5.5), therefore, the addition more coagulant dose might lead to decrease pH value to less than the standards. Hence, in order to achieve more reduction of COD and turbidity the coagulation period might be extended to more than one hour. However, the results for the coagulation with FeSO 4 noted that the maximum reduction of COD was observed with 30 mg L -1 while the increasing of concentrations to more than 30 mg L -1 associated with decreases in the removal percentage which indicating that the increasing of coagulation period might effect negatively on the chemical coagulation. In contrast the increasing of removal percentage with increasing of M. oleifera dose indicating that the increasing of time might also achieve high efficiency based on the concept of equilibrium between substrates and produces. The alternative way to achieve more reduction in both COD and turbidity is by perform a secondary coagulation process of supernatant results from the first coagulation process. The increasing in the coagulant dose or settling time might achieve the reduction levels required for the disposal process while, the adjusting pH of laundry wastewater might be unacceptable in terms of reduction of chemical additives for the treatment of wastes.

Conclusions
The results of COD, turbidity, pH and TSS indicate that the laundry wastewater have a different characteristics due to the presence of detergent compounds which lead to increase COD and pH values. M. oleifera seeds exhibited high efficiency for the removal of turbidity but not for the COD in comparison to FeSO 4 . However, M. oleifera seeds is eco-friendly since the sludge generated is consist of degradable substances. Both COD and turbidity still more than the standards A and B for the disposal of wastewater, but the increase the period of coagulation with M. oleifera seeds or the subjection for a secondary coagulation process might contribute in their reduction of these parameters to be within the standards limits. Nevertheless, these suggestion need to be investigated to confirm their effectiveness.