Discovering potential of different parts of Moringa oleifera’s plants as clarifying agent in coffee effluent treatment

Selection of coagulant for coagulation-flocculation treatment process involves more factors than we generally expect. Embracing emerging global concerns on green technologies and sustainability, researchers have been focusing on natural coagulant as an alternative to minimize environmental impact due to toxic chemical coagulants. Moringa oleifera has long been discovered as a highly potential agent in water clarification treatment, but most of the research done focuses only on the seeds of the plant. In this research, various parts of this plant species were studied namely soft stems, leaves, seeds and pods. These coagulants were prepared through drying and grinding methods, without any chemical activation or extraction to avoid unnecessary chemical burden on produced sludges or treated water after treatment. In treating coffee effluents, all these four coagulants from different parts (soft stems, leaves, seeds and pods) were able to remove good amount of turbidity compared to the control without coagulant. The performance of all four types of prepared coagulants were analyzed using jar test within similar dosage range to identify which part of M. oleifera that can serve the best coagulant. The highest removal of turbidity was achieved by the pods with 60-62% removal at a dosage as low as 0.03 and 0.04 g/L with 24-hour sedimentation. A similar range of turbidity removal was achieved by leaves coagulant at 0.06 g/L with similar operational conditions. These findings give evidence that different parts of M. oleifera plants possess good water clarifying ability, even better than the seeds that had been discovered beforehand.


Introduction
Nowadays, café serving coffee is considered as an essential need and represents one important key point to valuate region's developments.Aligned with current acceptance and pattern of coffee beverages consumption, coffee industry has been expanding years by years to fulfil respected demands and giving positive impact on national economic scenario.However, on the other side of this gratifying occasion, there is another side of concern that needs to be considered.Coffee production process has led to production of large volume of wastewater with high concentration of pollutants such as suspended solids and organic matters [1].Rural coffee producers usually discharge wastewater produced directly into nearby water sources without treatment due to lack of awareness towards sustainability of ecosystem, and also due to expensive technologies for treatment method.And this scenario contributes to water pollution and human health problem [2,3].Hence, this study had been focusing in treating coffee effluent using coagulation-flocculation treatment process which is technically simple and cheaper due to low manpower and experts needed [4].Conventional coagulants available in markets are usually from chemical-based resources [5].Utilization of this expensive coagulant will lead to environmental pollution and risk of human health after long time exposure; also production of toxic sludge which requires post waste management [6,7].To further reduce the operational cost, coagulants in this research were produced from natural resources such as plants which are more environmentally friendly and easy to access [8].Parts of Moringa oleifera plant were chosen as coagulant due to its abundant availability in Malaysia, and easy cultivation for larger usage.

Wastewater collection and characterization
Industrial coffee processing effluent (indicated as coffee effluent onwards) was collected directly from a wastewater collection pond of a coffee processing plant in Pulau Pinang, Malaysia.Coffee effluent in polyethylene container was then stored in a greenhouse environment at an average temperature of 37℃.Before further experimental run, coffee effluent was characterized in terms of pH and turbidity using pH meter HQ11d (HACH, USA) and turbidimeter 2100 AN (HACH, China).

Preparation of coagulant from Moringa oleifera parts
Soft stems, leaves, seeds and pods of M. oleifera (Figure 1) was collected by the roadside of Bandar Baru Bangi region in Selangor, Malaysia.All samples were cleaned from any foreign matter and separated accordingly.All samples were washed individually with distilled water followed by drying process in laboratory dryer at 40 ℃ for 48 hours to remove its moisture content.Dried samples were then crushed into smaller particles using a domestic dry blender and sieved to collect uniform size of <1 mm.All the stems, leaves, seeds and pods of M. oleifera coagulant powder were stored individually in airtight containers until further usage.
Fresh coagulant stock solution was prepared right before any jar test experiment.A 1 g/L stock solution was prepared by mixing 1 g of respected coagulant powder in 1 L of distilled water and stirred into uniformity using magnetic stirrer for 45 minutes.The solution is then centrifuged at 4000 rpm for 10 minutes to separate liquid and powder layers.Next, the solution was filtered using vacuum pump to collect the final supernatant as coagulant stock solution.

Figure 1
Parts of M. oleifera plants used as coagulant 3

Jar test set-up
Jar test set-up is usually used to test the performance of coagulation activity in turbid water treatment.
In this research, a jar test with different dosage of 0.03 to 0.06 g/L was operated for each type of coagulant.A total volume of 400 mL mixture of coffee effluent and coagulant solution was loaded in 500 mL beakers, with different ratio of mixing to achieve desired dosage.Formulation used to calculate the dosage is represented in Equation 1.For instance, a dosage of 0.04 g/L is achieved by mixing 16 mL of prepared coagulation stock (1 g/L) into 384 mL coffee effluent to achieve a total of 400 mL.A beaker with 400 mL of coffee effluent with similar operating condition was used as a control set up for performance comparison.A jar test operation consists of three phases which are rapid mixing, slow mixing and sedimentation phases.Rapid mixing was done at 150 rpm for 2 min, followed by slow mixing at 40 rpm for 20 min.The solution was let to settle for a sedimentation process for 24 h [9], modified from a research work by Murugandam [9].Supernatant was collected using pipette about 1 cm from the surface after sedimentation process for further analysis.Supernatant was analyzed for the same parameters as effluent characterization which were pH and turbidity.The best coagulant was chosen based on its removal performance compared to its initial characterization of coffee effluent.In general, coagulant with lower dosage but higher removal performance was identified as the best in terms of economic and efficiency.

Performance of coagulants in coffee effluent treatment
Performance of for all four different parts of M. oleifera plants was evaluated based on the outcomes of jar test experimental run.Figure 2 shows the initial and final concentration of coffee effluents' turbidity with its respected removal percentage.All coagulants showed higher removal efficiency than the control set-up, concluding that all coagulants gave positive effect in treating coffee effluents.Pods and leaves show the highest turbidity removal in the range of 56 to 62%, compared to seeds and stems with 33 to 44%.Pods of M. oleifera show the highest removal at 0.04 g/L (62%) with only 1% difference with the smallest dosage of 0.03 g/L; and declined to 56% at higher dosage.This showed that optimal concentrations of this coagulant lie between 0.03 and 0.04 g/L for coffee effluent treatment.While leaves of M. oleifera showed the highest removal of 60% at a dosage of 0.06 g/L.Turbidity removal by the pods showed increasing trend, indicating possibility of higher dosage as the best dosage for coffee effluent.Hence, pods of M. oleifera were chosen as the best coagulant for turbidity removal in coffee effluents since it achieved higher removal at lower dosage, comparable to leaves at higher coagulant concentration.Thus, a smaller number of raw materials is needed, relative to the amount of wastewater to be treated and leads to cost savings.

Figure 2
Efficiency of coagulant in coffee effluent treatment Others similar study by Natumanya and Okot-Okumu [10] showed seed of M. oleifera extracted using NaCl was able to reduce 98% in treating drinking water.These significant findings show that chemical extraction contributes greatly to creating anion and cation interaction that helps in coagulationflocculation process.Amruta and Munavalli [11] studied ability of aloe vera coagulant extracted by water in treating synthetic turbid water, and able to achieve 81% of turbidity removal.While this study achieves highest removal at 62% using pods of M. oleifera extracted by water.Direct comparison cannot be done since there is no similar study found within this scope in treating coffee effluent.Generally, coffee effluent is more turbid than those drinking and synthetic water; with higher amounts of soluble and insoluble solids that increase the complexity of the treatment.This coagulation-flocculation process does not alter the pH in wastewater significantly as shown in Figure 3, representing the pH change in the two best coagulants studied which are pods and leaves of M. oleifera, demonstrating that there is no significant changes in H + ion content occurred in the treatment [12].A study by Temitope et al. [13] used powdered M. oleifera coagulant to treat turbidity of restaurant wastewater and achieved 88% of removal efficiency.

Figure 3
Change in pH after coagulation-flocculation process

Conclusions
To highlight a greener solution for wastewater treatment, this study develops four coagulants from natural resources which are parts of Moringa oleifera plants, without any chemical extraction involved.
The four parts studied are pods, seeds, leaves and soft stems.Observation from jar test experiments showed that coagulant from pods and leaves show the highest removal ability of coffee effluent turbidity.Highest turbidity removal achieved at 0.04 g/L of M. oleifera pods with 62% of removal.There is change in pH before and after coagulation-flocculation process for coffee effluent.