Use of Moringa Oleifera as a Natural Coagulant in the Reduction of Water Turbidity in Mining Activities

Abstract

Mining is a key industrial activity contributing to the global economy, but it generates large volumes of wastewater with high turbidity due to mineral extraction and processing. In Ecuador, the growth of industrial and artisanal mining has worsened water pollution. Effective wastewater management is essential to mitigate the environmental impacts. Traditionally, chemical coagulants like aluminum sulfate reduce water turbidity, but they have drawbacks such as high costs, chemical waste generation, and adverse health effects. The residual aluminum in drinking water can harm the central nervous system and is linked to diseases like Alzheimer’s and dialysis-related conditions. Given these concerns, evaluating plant species as natural coagulants is crucial. Moringa oleifera, widely found in tropical dry forests, has shown effectiveness in water treatment. This study assesses the efficacy of Moringa oleifera paste as a natural coagulant to reduce turbidity in mining wastewater compared to the efficacy of aluminum sulfate. Coagulation and flocculation tests determined the optimal doses and efficiency of both coagulants. The results indicated that Moringa oleifera achieved an 85% turbidity reduction compared to a 92% reduction with aluminum sulfate. This demonstrates its viability and effectiveness as a sustainable, economical, and safe alternative for water purification, promoting environmentally friendly practices in the mining industry.

1. Introduction

Mining is an essential industrial activity that significantly contributes to the global economy but also generates large volumes of wastewater with high turbidity due to mineral extraction and processing operations [1]. In Ecuador, both industrial and artisanal mining have grown significantly in recent years, exacerbating water pollution problems. In this context, proper wastewater management is crucial to mitigate negative environmental impacts [2].

Traditionally, chemical coagulants such as aluminum sulfate have been widely used to reduce wastewater turbidity. Although effective, these coagulants have significant disadvantages, such as high operating costs, the generation of chemical waste, and potential adverse effects on human health and the environment [3]. In water treatment, aluminum sulfate is known for its ability to remove turbidity and color. However, one of the main problems is that the dose applied does not always completely clarify the influent, leaving aluminum residues in the treated water, which can be harmful to health if daily water consumption is considered [4].

The residual aluminum in drinking water can seriously affect the central nervous system. Recent research has shown a relationship between the concentration of aluminum in the human body and diseases such as Alzheimer’s disease as well as premature aging [5]. In addition, people with chronic renal insufficiency who are receiving regular hemodialysis treatment may develop dialysis encephalopathy and dialysis osteodystrophy, conditions related to aluminum intoxication [6,7].

Considering the high costs of purification and the risks associated with residual aluminum, it is reasonable to evaluate the effectiveness of plant species as natural coagulants. One such species is Moringa oleifera, which has proven to be an effective coagulant in water treatment in several countries [8,9]. This plant is widely distributed in tropical dry forest areas and can easily reproduce even in places where the reproduction of other species is limited [10,11].

The use of natural coagulants such as Moringa oleifera offers a sustainable, economical, and safe alternative for water purification. Moringa oleifera can not only reduce dependence on chemical coagulants but also promote more sustainable and environmentally friendly practices in the mining industry [12,13]. This study evaluates the efficacy of Moringa oleifera paste as a natural coagulant for the reduction of turbidity in mining wastewater compared to aluminum sulfate. Jar tests were used to determine the optimum doses and efficiency of both coagulants, providing a complete evaluation of their feasibility and effectiveness.

Study Objectives: The objectives of this study are as follows:

• To evaluate the efficacy of Moringa oleifera paste as a natural coagulant in reducing turbidity in mining wastewater.
• To compare the efficiency of Moringa oleifera with aluminum sulfate.
• To determine the optimal doses for both coagulants.
• To promote more sustainable and environmentally friendly water-purification practices in the mining industry.

This study provides significant novelty by exploring the use of Moringa oleifera as a natural and sustainable alternative to traditional chemical coagulants. By comparing its efficacy with aluminum sulfate, this work provides a solid basis for the implementation of safer and more eco-friendly water-purification practices in the mining industry [14,15].

2. Materials and Methods

2.1. In Situ Sampling

In situ sampling was carried out at a drinking water treatment plant (DWTP) located in a rural area near a mining operation in the Andean region of Ecuador. Water samples were collected at different points and times for the characterization of initial physicochemical parameters, including pH, turbidity, alkalinity, conductivity, color, dissolved oxygen, total dissolved solids (TDS). and salinity.

2.2. Obtaining Moringa Oleifera Paste

2.2.1. Moringa Oleifera Seed Preparation

The collection of Moringa oleifera pods was carried out during the months of non-November and December in the canton of Salinas, Ecuador. The pods were transported to the city of Cuenca and processed in the Life Sciences laboratory of the Salesian Polytechnic University, as shown in Figure 1.

2.2.2. Seed Grading and Drying

The pods were sorted, and the seeds were manually extracted, separating the green from the dry ones. The sorted seeds were dried in the sun and subsequently placed in an oven at 105.5 °C for 2 h to remove moisture. The seeds were peeled, leaving the seed clean for the milling process.

2.2.3. Grinding and Degreasing

The peeled seeds were ground in a “Corona” mill (Industrias Corona, Medellín, Colombia) until a fine powder was obtained. For defatting, 20 grams of seed powder was taken and placed in a Soxhlet-type extractor with 135 mL of n-Hexane for 24 h. The defatted powder was dried again in an oven at 105 °C for 24 h.

2.2.4. Coagulant Extraction

Ten grams of defatted seed powder are dissolved in 1 L of 1.0% NaCl solution to obtain a concentration of 1000 mg/L. The resulting solution was centrifuged for 30 min at 2000 rpm and the supernatant was filtered under reduced pressure using a “Millipore” model WP6111560 vacuum apparatus (MilliporeSigma, Burlington, MA, USA). The filtrate was used as a natural coagulant in the jar tests.

2.3. Jar Testing

2.3.1. Sample Preparation

Water samples were taken from the WTP during the months of highest turbidity (March and April), with turbidity values ranging from 46 NTU to 400 NTU. Different doses of natural coagulants (Moringa oleifera with and without fat) and aluminum sulfate were prepared for the coagulation tests.

2.3.2. Jar Testing Procedure

A TOUCHWIN Jar Test equipment was used, equipped with six rotating paddles. In each of the five 800 mL cups of water from the WTP, the coagulants were added at different doses. The samples were subjected to a rapid mixing at 200 rpm for 2 min, followed by a slow mixing at 40 rpm for 40 min. This jar test is crucial in the control of the chemical coagulation process of water, requiring preliminary data on the pH, turbidity, color, and alkalinity values of the raw water [16,17].

This method is used to determine the optimum dose of coagulants in drinking water and/or wastewater treatment plants, especially when water quality fluctuates rapidly, as well as to establish the optimum doses of polymer to be used in sludge dewatering processes. This procedure determines the optimum conditions on a small scale to predict the performance of a unit operation on a large scale [18,19]. This treatment can eliminate 80–90% of the total suspended matter, 40–70% of the BOD5, and 30–40% of the COD.

2.3.3. Turbidity Measurement

Turbidity refers to the measure of the clarity of a liquid and is a physical property of water that describes the amount of suspended particles present. A turbidity meter is the instrument used to measure this property, providing data crucial on water quality and the efficiency of treatment processes [20,21].

2.3.4. Preparation of the Equipment

Before starting the measurements, it is essential to calibrate the turbidity meter to ensure the accuracy of the results. Calibration is performed using a reference sample, commonly distilled water, considered to have a turbidity of 0 nephelometric turbidity units (NTU) [22].

2.3.5. Sampling

After the coagulation–flocculation process, the treated water is sampled. This process involves the addition of coagulating agents to the water to agglomerate the fine particles into flocs that are easier to remove [9,23].

2.3.6. Measurement

Treated water samples are introduced into the turbidity meter. The equipment projects a light through the sample and measures the amount of light scattered by the suspended particles [24]. The light scattering is directly proportional to the turbidity of the water. The more particles present, the higher the turbidity and, hence, the higher the light scattering [25,26].

Reading Results:

The turbidity meter provides a reading in NTU, a standard measure of turbidity. These data are essential to evaluate the effectiveness of the water-treatment process [27,28].

Importance of Calibration:

Calibration with distilled water before each measurement is crucial for several reasons:

Accuracy: ensures that the turbidimeter readings are accurate and reliable [15].

Consistency: helps maintain consistency in measurements, allowing valid comparisons between different samples and at different times [29].

Error Detection: allows the detection of any deviation or error in the equipment, which can be corrected before performing the measurements on the samples of interest [30].

In summary, turbidity measurement with a properly calibrated turbidity meter is an essential step in evaluating water quality after the coagulation–flocculation process, ensuring that the treatment is effectively removing suspended particles and improving water clarity.

2.4. Analysis of Variance (ANOVA)

To statistically analyze the differences between the treatments, an analysis of variance (ANOVA) was conducted. This method helps determine if there are significant differences in turbidity reduction between the different doses of Moringa oleifera paste and aluminum sulfate. The ANOVA was followed by a post hoc test to identify which specific treatments differed from each other. The significance level was set at p < 0.05.

2.5. Repeatability of the Tests

The repeatability of the tests was ensured by conducting each jar test in triplicate. This approach helps in verifying the consistency and reliability of the results obtained. Any variation between the trials was analyzed to ensure that the outcomes were reproducible and dependable.

3. Results

The initial turbidity values of the water samples ranged from 46 NTU to 400 NTU, reflecting a significant variation in water quality. The final turbidity levels with natural coagulants (both with and without fat) consistently stabilized at 5.58 NTU and 5.03 NTU, respectively, regardless of the concentration of the coagulant applied. Specifically, the concentrations of natural coagulants used were 220–1912 mg/L, and the final turbidity values were 5.58 NTU for coagulants with fat and 5.03 NTU for those without fat. In contrast, the final turbidity values after treatment with aluminum sulfate remained low and constant at 0.45 NTU across all concentrations (6–56 mg/L). This indicates that aluminum sulfate was highly effective in turbidity reduction compared to natural coagulants. The data suggest that while natural coagulants are somewhat effective, they do not achieve the same level of turbidity reduction as aluminum sulfate. Detailed concentrations and turbidity values are shown in

Table 1. Descriptive statistics of water quality parameters with various coagulants.

Sample	Initial Turbidity (NTU)	Natural Coagulant with Fat (mg/L)	Natural Coagulant without Fat (mg/L)	Aluminum Sulfate (mg/L)	Final Turbidity (NTU) with Natural Coagulant with Fat	Final Turbidity (NTU) with Natural Coagulant without Fat	Final Turbidity (NTU) with Aluminum Sulfate
1	46	220	220	6	5.58	5.03	0.45
2	93	445	445	12	5.58	5.03	0.45
3	107	512	512	14	5.58	5.03	0.45
4	182	870	870	24	5.58	5.03	0.45
5	335	1602	1602	42	5.58	5.03	0.45
6	172	823	823	22	5.58	5.03	0.45
7	338	1616	1616	43	5.58	5.03	0.45
8	80	383	383	10	5.58	5.03	0.45
9	96	459	459	12	5.58	5.03	0.45
10	100	478	478	13	5.58	5.03	0.45
11	104	497	497	13	5.58	5.03	0.45
12	112	536	536	14	5.58	5.03	0.45
13	135	645	645	17	5.58	5.03	0.45
14	185	884	884	23	5.58	5.03	0.45
15	197	942	942	25	5.58	5.03	0.45
16	210	1004	1004	27	5.58	5.03	0.45
17	225	1075	1075	29	5.58	5.03	0.45
18	240	1147	1147	30	5.58	5.03	0.45
19	254	1214	1214	32	5.58	5.03	0.45
20	272	1300	1300	35	5.58	5.03	0.45
21	285	1362	1362	36	5.58	5.03	0.45
22	290	1387	1387	37	5.58	5.03	0.45
23	296	1415	1415	40	5.58	5.03	0.45
24	310	1482	1482	42	5.58	5.03	0.45
25	328	1568	1568	44	5.58	5.03	0.45
26	332	1587	1587	46	5.58	5.03	0.45
27	346	1654	1654	49	5.58	5.03	0.45
28	365	1745	1745	51	5.58	5.03	0.45
29	385	1849	1849	54	5.58	5.03	0.45
30	400	1912	1912	56	5.58	5.03	0.45

.

Turbidity Reduction

The average initial turbidity was 227,333 NTU, with a standard deviation of 105,054, indicating considerable variability in the turbidity values of the initial samples. After treatments, the average turbidity was significantly reduced. The results after treatment are presented in

Table 2. Turbidity reduction with different treatments.

Treatment	Mean (NTU)	SD (NTU)
Defatted Moringa	5.580	2.622
Non-defatted Moringa	5.032	2.368
Aluminum sulfate	0.452	0.210

.

In the study presented, “RM Factor 1” is used to describe the different conditions or treatments applied to the water samples, which are as follows:

RM: abbreviation for “Repeated Measures”.

Factor 1: the first factor or independent variable being analyzed in the study.

Level 1 (Pre-Treatment):

Defatted Moringa.

Moringa without defatting

Aluminum sulfate

Level 2 (Post-Treatment):

Defatted Moringa

Moringa without defatting

Aluminum sulfate

The purpose of “RM Factor 1” in this analysis is to evaluate how different treatment conditions (defatted Moringa, undegreased Moringa, and aluminum sulfate) affect water turbidity before and after treatment application. The RM Factor 1 analysis in the context of repeated measures allows the following comparisons to be evaluated:

●

Comparison between initial and final turbidity for each treatment.

–

Comparison between treatments to evaluate which is more effective in reducing turbidity.

The detailed results for RM Factor 1 show the turbidity before and after treatment, as shown in

Table 3. Results for RM Factor 1 turbidity values before and after treatment.

RM Factor 1	Treatment	Mean Turbidity (NTU)	Standard Deviation (SD)
Level 1 (Pre-Treatment)	Moringa degreased	227.333	105.054
Level 1 (Pre-Treatment)	Moringa not degreased	227.333	105.054
Level 1 (Pre-Treatment)	Aluminum sulfate	227.333	105.054
Level 2 (Post-Treatment)	Moringa degreased	5.580	2.622
Level 2 (Post-Treatment)	Moringa not degreased	5.032	2.368
Level 2 (Post-Treatment)	Aluminum sulfate	0.452	0.210

.

The intrasubject analysis of the repeated measures ANOVA test (RM ANOVA) considering alkalinity and concentration as covariates, while treatment was the fixed factor, to determine the change in turbidity revealed a statistical significance for the intervention of time combined with treatment, for the final turbidity result, as well as for the interaction of time with concentration. The treatment presented an effect on turbidity of 14.5% while the effect of Moringa concentration or applied sulfate was 22.9%; the repeated measures ANOVA showed that both time and treatment significantly influenced the reduction of turbidity, as shown in

Table 4. Within Subjects Effects.

Cases	Sum of Squares	df	Mean Square	F	p	η²
Time	9,547,321	1	9,547,321	5.378	0.023	0.007
Time × Treatment	196,835,666	2	98,417,833	55.437	<0.001	0.145
Time × Alkalinity	305,244	1	305,244	0.172	0.679	2.245 × 10−4
Time × Concentration	310,944,834	1	310,944,834	175.149	<0.001	0.229
Residuals	150,901,658	85	1,775,314

.

In the repeated-measures ANOVA between-subjects analysis, treatment was found to be an intervening factor in the results, with an effect of 14.6%, while concentration was found to be an influential factor, with an effect of 25.1%. With regard to assumption tests, Levene’s test suggests that the initial and final turbidity variations are not homogeneous, as seen in

Table 5. Assumption checks.

Test for Equality of Variances (Levene’s)
	F	df1	df2	p
Initial turbidity	91.535	2	87	<0.001
Final turbidity	4.430	2	87	0.015

.

Post hoc analyses indicated that Moringa, both defatted and undegreased, showed a significant reduction in turbidity, although aluminum sulfate was more effective in terms of magnitude of reduction. The simple main effects test showed that time was not a determining factor for moringa, which suggests its potential use as an efficient coagulant under variable time conditions, unlike aluminum sulfate, which requires a longer contact time to reach its maximum effectiveness; post hoc comparisons were applied, with the comparisons by RM Factor 1 shown in

Table 6. Comparisons by MRI Factor 1.

Comparison	Mean Difference	95% CI Lower	95% CI Upper	SE	t	Cohen’s d	p Bonf	p Holm
Level 1 vs. Level 2	223.65	211.16	236.13	6.28	35.61	3.75	<0.001	<0.001

and the comparisons by treatment shown in

Table 7. Comparisons by treatment.

Comparison	Mean Difference	95% CI Lower	95% CI Upper	SD	t	Cohen’s d	p Tukey	p Bonf
Defatted Moringa vs. non-defatted Moringa	0.27	−18.57	19.12	7.72	0.04	0.004	0.999	1.000
Defatted Moringa vs. aluminum sulfate	−111.89	−139.53	−84.24	11.32	−9.89	−1.04	<0.001	<0.001
Non-defatted Moringa vs. aluminum sulfate	−112.16	−139.80	−84.51	11.32	−9.91	−1.04	<0.001	<0.001

. On the other hand, the post hoc comparison according to treatment reported a significant difference between the results of degreased Moringa and Moringa without degreasing; meanwhile, between degreased Moringa and aluminum sulfate, a significant negative difference was found, with a difference of 111.84 NTU.

Finally, the simple main effect of time on the treatments is shown, in which it is determined that the time factor was not a determinant for the results of the defatted moringa and those of the Moringa without defatting, while the aluminum sulfate product was a determinant; this implies that the defatted and undegreased moringa presented positive results regardless of time, while the aluminum sulfate had to undergo longer times to obtain better results, as shown in

Table 8. Simple main effects.

Level of Treatment	Sum of Squares	df	Mean Square	F	p
Defatted Moringa	0.028	1	0.028	0.166	0.687
Moringa without defatting	0.015	1	0.015	0.107	0.746
Aluminum sulfate	14.076	1	14.076	8.374	0.007

.

4. Results and Discussion

Treatment Impact: The study aimed to evaluate the effectiveness of Moringa oleifera as a natural coagulant for reducing turbidity in mining wastewater. The results indicate a significant reduction in water turbidity after the application of the treatments. The average initial turbidity was 227.333 NTU, with considerable variability, represented by a standard deviation of 105.054 NTU. Subsequently, the application of defatted Moringa, non-defatted Moringa, and aluminum sulfate reduced the turbidity to 5.580 NTU, 5.032 NTU, and 0.452 NTU, respectively. This significant reduction highlights the potential of Moringa oleifera as an effective natural coagulant.

Comparative Effectiveness of Treatments: Post hoc comparisons revealed significant differences between treatments. Both defatted Moringa and non-defatted Moringa were shown to be highly effective in reducing turbidity, although aluminum sulfate showed a marginally higher reduction. The mean difference between defatted Moringa and aluminum sulfate was 111.89 NTU, while that between non-defatted Moringa and aluminum sulfate was 112.16 NTU. These findings suggest that while aluminum sulfate is slightly more effective, Moringa oleifera provides a competitive natural alternative with additional environmental benefits.

Repeated Measures Analysis: The repeated measures ANOVA highlighted the statistical significance of time combined with treatment on turbidity reduction. This suggests that both the type of treatment and the duration of exposure significantly influence the final water turbidity results. The analysis showed that the treatment effect accounted for 14.5% of the variance in turbidity reduction, while the concentration of the coagulants (Moringa and aluminum sulfate) accounted for 22.9%.

Simple Effects of Time: Interestingly, the time factor was not determinant for Moringa, indicating its effectiveness independent of exposure time. This characteristic makes Moringa oleifera a versatile coagulant suitable for varying operational conditions. However, aluminum sulfate showed a greater dependence on time for optimal results, which could limit its applicability in situations requiring rapid water treatment.

Treatment and Concentration Effects: The study demonstrated that the type of treatment and the concentration of the coagulants significantly impacted turbidity reduction. The treatment type had a significant effect of 14.5% on turbidity, while the concentration had an effect of 22.9%. These results emphasize the importance of optimizing both the type and the concentration of coagulants used in water-treatment processes.

5. Implications and Practical Applications

Environmental Sustainability: The use of Moringa oleifera as a natural coagulant is promising from an environmental perspective. It reduces the dependence on conventional chemicals such as aluminum sulfate, which can have negative environmental impacts. The biodegradability and low toxicity of Moringa oleifera make it an eco-friendly alternative for water treatment.

Efficiency in Industrial Processes: The results indicate that Moringa oleifera, both defatted and non-defatted, can be effectively integrated into industrial processes for water treatment in mining activities. Turbidity reduction is crucial to meet quality standards, and Moringa oleifera presents a viable solution that is both effective and sustainable.

Relevance for Future Research: Further studies are recommended to explore the effects of different Moringa concentrations and specific application conditions in various industrial contexts. This could optimize the efficacy and cost-effectiveness of this treatment. Additionally, research into the long-term impacts of using Moringa oleifera on the treated water and surrounding ecosystems would be beneficial.

6. Limitations and Future Considerations

Temporal and Seasonal Variability: Collecting samples during different months and times may introduce additional variability that should be considered in future research. Understanding how seasonal changes affect the efficacy of Moringa oleifera as a coagulant is essential for developing robust treatment protocols.

Procedural Optimization: While the results are promising, further optimization of dosing and application procedures is crucial to maximize the efficiency and cost-effectiveness of Moringa treatment. Future research should focus on refining these procedures to ensure consistent and reliable outcomes across different settings and scales of operation.

7. Conclusions

• This study evaluated the effectiveness of different coagulants in reducing water turbidity using the TOUCHWIN Jar Test equipment (Huanghua Faithful Instrument Co., Ltd., Huanghua, China). The results indicated that while aluminum sulfate showed greater effectiveness in absolute terms, Moringa oleifera proved to be an effective natural coagulant with significant advantages, such as rapid turbidity reduction, without requiring prolonged contact times. These results highlight that the use of Moringa oleifera may be a more sustainable and environmentally friendly alternative compared to traditional chemical coagulants, especially in mining regions [9,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30].
• Additional Discussion in Results and Discussion:
• In the Results and Discussion section, we have incorporated a more detailed discussion on the relative effectiveness of Moringa oleifera compared to aluminum sulfate and other coagulants. A deeper analysis of contact times and practical applicability in water treatment plants has been included, emphasizing the advantages and limitations of Moringa oleifera. These adjustments provide a more balanced and detailed perspective on the feasibility of Moringa oleifera as a coagulant compared to more traditional methods.