Enhancing the agronomic value of dry faecal sludge for agricultural soil amendment by adding natural phosphate rock and other local substrates in Burkina Faso

doi:10.21203/rs.3.rs-5319684/v1

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Enhancing the agronomic value of dry faecal sludge for agricultural soil amendment by adding natural phosphate rock and other local substrates in Burkina Faso

https://doi.org/10.21203/rs.3.rs-5319684/v1

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Raw dry faecal sludge in Burkina Faso is commonly used for agricultural soil amendment. Due to its acidity, this application may lead to various forms of soil degradation. The current study aimed to investigate rapid and sustainable agricultural valorization of dry fecal sludge in farming systems through different formulations of dry sludge-based manure. For this purpose, we prepared composite samples of dry faecal sludge from the Dogona station in western Burkina and seven formulations of dry faecal sludge-based manures. Dry faecal sludge amended with natural phosphates, montmorillonite, slaked lime and zinc ore were analyzed for their physicochemical, biochemical, pathogenetic and toxicological properties to evaluate their suitability as agricultural amendment. The results outlined that dry faecal sludge, although having a high organic matter content (25.34 ± 0.09 to 40.97 ± 9.99%), adversely affected soil structural stability because of its low pH (4.58), a low C/N ratio (10.03) and a very high COD/BOD5 ratio of 5.00. However, their content in trace metal elements (Cu, Zn, Cd, Pb, Cr and Ni) and pathogens (helminth eggs, coliforms and fecal streptococci) were in a range favorable for being used as manure. The different formulations of manures proved to be better organo-mineral amendments compared to raw sludge due to improved properties. The pH was significantly higher (between 7.24 and 7.72), the C/N ratio increased (ranging from 9.40 to 10.09) and the biodegradability indicator COD/BOD5 was significantly lower as well (r2.39 to 2.71). Our results showed that dry faecal sludge amended with local substrates gives new prospects for using these formulations as fertilizers in sustainable soil fertility management while contributing to waste recycling and environmental protection.

Burkina Faso

Dogona

natural phosphates

montmorillonite

slaked lime

In sub-Saharan Africa, soil degradation initiated by adverse climatic conditions is often exacerbated by anthropogenic factors such as miss-use of soil resources (Sanou et al., 2018 ; Bouzelha, 2020). Indeed, the area of farm lands, estimated to be 0.19 ha per inhabitant in 2017, decreased by 20% in 2020, due to population pressure and climatic disasters (FAO, 2021). In lixisoils under tropical climates, organic matter depletion due to physical soil degradation is characteristic and it is mainly caused by climatic factors such as temperature (Traoré et al., 2020). In addition, other socio-economic contexts like poor physical and/or economical access to organic and mineral fertilizers also fragilizes farming systems in general and reduces soil quality due to poor recycling of nutrients exported through harvests (Traoré et al., 2019). Due to its key role in household income generation, soil degradation, whether from natural or anthropogenic origin, threatens population life with unpredictable consequences both economically and socially. According to UNCCD (2018), land degradation may cause an annual yields loss of 30% in West Africa. From an economical point of view, the annual cost of land degradation is estimated at more than 18.9 billion US dollars and costs for mineral fertilizers are increasing (Nkonya et al., 2016; Cissé et al., 2021).

To address the problem of soil degradation, several approaches have been implemented and, the production and use of organic manure have been widely promoted as endogenous practice. These endogenous practices of soil fertility management focused mainly on improving the soil organic matter stock in agricultural soils, through fertilization approaches and soil conservation (Pouya et al., 2020). For its high content in organic matter, sanitation by-products such as dry faecal sludge are increasingly used in agrosystems as organic manure (Koné et al., 2016). In most of the cases, they are directly applied on agricultural soils or after co-composting with crops residues. However, the direct application of dry faecal sludge presents risks of contamination and long-term soil degradation (Maya et al., 2012; Lo et al., 2019). Indeed, Héma et al. (2024), highlighted high acidity of the dry faecal sludges from the sludge treatment stations in Burkina Faso, which could compromise soil agronomic qualities. The applicability of using composted dry faecal sludges is limited due to its poor nutrient contents and fast mineralization rates as was shown for other types of compost widely investigated (Lompo et al., 2009). The present study aimed at developing formulations of organo-mineral amendments based on dry faecal sludge and local substrates while at the same time addressing environmental sanitation issues.

Organic substrate

The basic organic substrates were classified into three types of dry faecal sludge, based on their storage duration in recent, intermediate and old faecal sludge, corresponding to a storage duration of less than 2 years, between 2 and 3 years and longer than 3 years, respectively. The raw dry faecal sludge was collected at the station of Dogona (11° 12’ 17.1¨ N et 4° 16’ 49.3¨W), in the western part of Burkina Faso. The different classes of dry sludge were determined from investigations conducted using a semi-structured approach with the different groups of workers of the station. The physicochemical parameters of the different classes of raw sludge are outlined in Table 1.

Table 1

Physicochemical parameters of the different classes of raw dry faecal sludge
Storage duration	> 3 years	2 to 3 years		< 2 years
Parameters	Old faecal sludges		Intermediate faecal sludges	Recent faecal sludges
pH_H2O	5.96 ± 0.45	5.59 ± 0.38		6.53 ± 0.10
EC (mS.cm^− 1)	6.23 ± 1.38	5.76 ± 0.79		4.17 ± 0.49
OC (%)	23.76 ± 5.80	14.70 ± 0.05		17.71 ± 2.29
OM (%)	40.97 ± 9.99	25.34 ± 0.09		30.52 ± 3.95
N-tot (%)	2.22 ± 0.56	1.47 ± 0.07		1.70 ± 0.16
C/N ratio	10.74 ± 0.11	10.02 ± 0.47		10.41 ± 0.69
P-tot (mg.kg^− 1)	14234.32 ± 3442.41	11761.33 ± 1533.33		8595.24 ± 281.33
K-tot (mg.kg^− 1)	781.34 ± 33.07	519.40 ± 31.16		902.37 ± 38.98
Na (mg.kg^− 1)	103.34 ± 15.78	119.56 ± 16.12		652.88 ± 119.32
Ca (mg.kg^− 1)	8978.98 ± 2798.18	4118.16 ± 409.50		5350.92 ± 70.13
Mg(mg.kg^− 1)	2432.56 ± 35.55	2579.55 ± 1661.59		2467.39 ± 78.02
Source: Héma et al. (2022)

Additional local substrates used for improving the raw sludges agronomic quality

For the formulations of the different formulas of organo-mineral amendments, four local substrates, selected according to their economical and physical accessibility were mixed with the dry faecal sludges: natural phosphates from Kodjari (Burkina phosphate), montmorillonite clay, slaked lime and zinc. Slaked lime (Ca(OH)₂) with 95% solubility and a high CaO content (89.54%) was also used due to its ability to improve the acid-base status of organic substrates. In Burkina Faso, slaked lime is available and affordable. It was obtained from limestone extracted by the “Compagnie Villageoise de l’Exploitation Minière (COVEMI)”. The choice of slaked lime is justified by its ability to improve the acid-base status while reducing the acidity of dry fecal sludge, due to the action of carbonates on protons (H⁺)

The natural phosphates from Kodjari (BP) were from the phosphate mining company in Burkina Faso. They were extracted in the Kodjari deposit, a village located in the south-east of the Burkina, in the province of Tapoa (11°50'22'' North; 1°54'59 '' East). The physicochemical composition of Kodjari natural phosphate is recorded in Table 2. Due to the poor phosphorus content of the majority of the soils in Burkina Faso, the natural phosphates from Kodjari are commonly recommended for its single use as amendment or for improving organic manure quality.

Table 2

Physicochemical parameters of natural phosphates from Kodjari
Chemical parameters	P₂O₅	Fe₂O₃	A1₂O₃	MgO	SiO₂	CaO	Na₂O	K₂O	F	S	CO₂
Content (%)	25.40	3.40	3.10	0.27	26.20	34.50	0.11	0.23	2.5	0.04	1.00
Source : (Roy et McClellan, 1986)

The montmorillonite clays used as a binder were collected from euthric Brunisoil (WRB, 1995) in Manga district (11° 40' 12'' North; 1° 04' 01'' West), in the South-Central Region of Burkina Faso. Zinc ore, used as a chemical additive, was from the Perkoa mine, in the Sanguié province (12° 22' 25'' North; 2° 35' 51'' West), Central-West region of Burkina Faso.

Formulation of organo-mineral amendments

The different organo-mineral amendments were formulated by combining raw dry faecal sludge (DFS) with various rates of the above-mentioned local substrates. As for the raw faecal sludge, a composite sample, obtained from the three classes of sludge identified, was used during the formulation. In total, seven types of organo-mineral amendments have been formulated:

F0 (95% DFS + 2.50% Ca(OH)₂ + 2.50% zinc);
F1 (80% DFS + 2% BP ¹+ 15% Clay + 1% Ca(OH)₂ + 2% zinc);
F2 (70% DFS + 1.25% BP + 25+% Clay + 1.25% Ca(OH)₂ + 2.50% zinc);
F3 (95% DFS + 1% BP + 1% Ca(OH)₂ + 3% zinc);
F4 (70% DFS + 1.50% BP + 27.50% Clay + 0.50% Ca(OH)₂ + 0.50% zinc);
F5 (80% DFS + 2% BP + 15% Clay + 2.00% Ca(OH)₂ + 1% zinc);
F6 (95% DFS + 2% BP + 1.50% Ca(OH)₂ + 1.50% zinc).

The physicochemical parameters of the different formulations were determined as well as biological, biochemical and pathogenic parameters. The biochemical and pathogenetic analyzes were conducted in the biochemistry and microbiology laboratory of the University Joseph KI ZERBO of Ouagadougou (Burkina Faso). Concerning the physicochemical analyses, they were carried out in the laboratory of the Institute of Soil Sciences, at the University of Natural Resources and Life Sciences, in Vienna (Austria). Furthermore, an assessment of the trace metal element content of these formulations was carried out to make sure that they meet the standards for being used as amendment in agriculture.

Physicochemical characterization of organo- mineral amendments

The different parameters were determined on air-dried, sieved (< 2 mm) samples. Electrical conductivity (EC) and pH were measured in water extracts at a substrate-to-solution ratio of 1:10 (w:v). The total organic carbon (TOC) and total nitrogen (TN) contained in the different formulations were determined by dry combustion using a flash elemental analyzer (Tabatabai and Bremner, 1991). Inorganic carbon was measured gas-volumetrically (Soil Survey Staff 2004) and organic carbon was calculated by the difference between total and inorganic carbon. Available phosphorus (P_CAL) and potassium (K_CAL) was determined according to Wuenscher et al. (2015) in CAL (Calcium-Acetate-Lactate) extracts. The potential cation exchange capacity of the different formulations was determined from the sum of calcium, magnesium, potassium, sodium, iron, aluminum and manganese after extraction with 0.1 M barium chloride solution buffered at pH = 8.1

Organic matter mineralization rate in the different formulations

The organic matter mineralization rate in the different formulations was determined by the buried bag method. In detail, 50 g of each formulation were buried at a depth of 20 cm in two soil types: Endopetric Lixisoil and Chromic Lixisoil. For the process, three mineralization bags per formulation of organo-mineral amendment were prepared and buried in each type of soil for two production campaigns corresponding to 20 months. After incubation, the buried bags were carefully removed from the soil without damaging them and away from any contamination sources. The contents of the buried bags were then sorted manually before being dried at 35°C for 72 hours. After drying, organic matter contents were obtained using the complete combustion method and the amount of organic matter was calculated according to the following Eq. 1:

$$\:MOR\:\left(\%\right)=\frac{initial\:OM-final\:OM}{initial\:OM\:}*100\:\:\left(Equation\:1\right)$$

Where,

MOR (%): Mineralization rate of the organic matter

Initial OM (%): organic matter contained in the formulation before burial

Final OM (%): organic matter contained the formulation after burial.

Biochemical characterization of the formulations

The Chemical Oxygen Demand (COD) and Biochemical Oxygen Demand in five days (BOD5) give information on the biodegradability of the different formulations. These parameters were obtained by measuring the COD using the volumetric/spectrometric approach according to the ISO 15705 (2002) standard, after dissolving the samples in distilled water at the ratio 1:5 (w:v). The solution obtained was filtered and the filtrate dosed with excess potassium dichromate (K₂Cr₂O₇) in sulfuric acid heated to 150°C for two hours in a heating block. BOD5 was determined respirometrically using Oxytops fixed to the vials for recording oxygen evolved by the catabolism of organic materials (Soro et al., 2020).

Determination of pathogenic load of the different formulations

Bacteriological analysis

The bacteriological analysis conducted on the different formulations were focused on faecal coliforms and faecal streptococci. These pathogens, at a certain threshold, are harmful to human health. It is therefore important to quantify these pathogens in the different formulations before using them as fertilizers or amendments in crop production. The quantification of faecal coliforms and streptococci was done by the mass inoculation method or cultural method, according to standard ISO 7218 (2007). A defined mass of each type of formulation was dissolved in distilled water and a series of dilutions of 1:10 in a final volume of 10 ml was prepared. A Plate Count Agar (PCA) culture medium was prepared and inoculated with the respective dilutions.

After inoculation, the culture medium was incubated at 44°C for 24 hours before counting the colonies. The number of Colony Format Units (CFU) per ml (or per g of product) was determined using Eq. 2:

$$\:\varvec{C}=\frac{\varvec{N}}{\varvec{V}\varvec{*}\varvec{d}}\varvec{*}100\:\:\left(Equation\:2\right)$$

where,

N: number of colonies counted

V: volume of inoculum applied to each box

d: dilution factor

Parasitological analysis

The parasitological analysis of the different formulations was conducted by quantification of helminth eggs (Ascaris lumbricid and Trichuris trichiura). Indeed, helminths colonize the human gastrointestinal tract and are therefore naturally found in faecal and subsequently in plant products. The concentration of parasites, particularly helminths, is a key indicator for determining the hygienic and safety status of organic substrates resulting from the treatment of faecal sludge (Ingellina et al., 2002). Helminth eggs concentrations were determined using the method developed by Bailenger and modified by WHO, (1997). The number of eggs per liter was calculated using Eq. 3:

$$\:\varvec{N}=\left(\varvec{A}\varvec{*}\varvec{X}\right)\:/\:\varvec{P}\varvec{*}\varvec{V}\:\left(Equation\:\:3\right)$$

where,

N: concentration of helminth eggs

A: number of eggs counted under the microscope

P: capacity of the McMaster blade

V = Initial sample volume

X = Volume of zinc sulfate-pellet mixture

Determination of trace metal element contents in the different formulations

The determination of the trace metal elements (TME) contained in the different formulations focused on concentration of copper (Cu), zinc (Zn), cadmium (Cd), lead (Pb), chromium (Cr) and nickel (Ni). Selected elements were extracted by hotplate aqua regia acid digestion. In detail, 0.5 g of ground oven-dried sample was mixed with 4.5 ml of 37% HCl and 1.5 mL of 65% HNO₃. All samples were heated to 150°C for 3 h following an 18 h reaction period at room temperature (Austrian Standards International, 2002). Subsequently, extracted elements were measured by inductively coupled plasma - mass spectrometry (ICP-MS, Agilent 7700).

Physicochemical characteristics of the formulations

Physicochemical parameters of the different formulations are summarized in Table 3. Acidity of the different formulations was in a suitable range for crop production which were 7.24 (F0) < pH < 7.75 (F1). As for raw faecal sludges, they were found to be too acidic for agricultural soil amendment (pH_H2O = 4.58). Total organic carbon and total nitrogen contents of the formulations as well as of dry faecal sludge showed high variability. Among formulations, the highest carbon content was recorded in F3 (125.3 g.kg^− 1) while (F2) had the lowest carbon concentration with 72.8 g.kg^− 1. Concerning nitrogen contained, it ranged from 7.3g.kg^− 1 to 12.6 g.kg^− 1, respectively, for F2 and F6 or F3. Phosphorus concentration in the different formulations ranged from 132.1 to 193.4 mg.kg^− 1 (respectively for F1 and F3), and potassium between 3326 to 5675 mg.kg^− 1 (respectively for F4 and F0). The cation exchange capacity (CEC) recorded in the different organic fertilizers ranged between 349.90 and 486.44 mmol.kg^− 1, respectively for F1 and F3. The trophic balance ratio C/N, providing information on the biodegradability of the different formulations, varied between 9.40 and 10.09 respectively for F0 and F4, with a value of 8.64 for the raw faecal sludge.

Table 3

Physicochemical parameters of the different formulations and the raw dry faecal sludge
Formulations	OM (%)	C (g.kg^− 1)	N (g.kg^− 1)	P (mg.kg^− 1)	K (mg.kg^− 1)	CEC (mmol.kg^− 1)	CaCO3 (%)	EC (µs/cm)	pH_H2O	C / N
F0	17.01	100.3	10.70	1995	5675	349.90	1.82	1781	7.24	9,40
F1	18.15	106.9	10.60	1321	4235	482.71	1.81	1139	7.75	10,09
F2	12.34	72.8	7.30	1060	3629	465.95	1.34	982	7.70	9,99
F3	21.36	125.3	12.6	1934	5202	486.44	1.73	1321	7.72	9,90
F4	15.32	90.1	9.00	1393	3326	448.07	1.40	910	7.71	10,02
F5	12.86	76.0	7.70	1530	3833	454.43	1.52	1123	7.68	9,82
F6	21.12	124.4	12.6	1722	4484	466.03	2.20	1395	7.65	9,84
raw faecal sludge	28.28	164.2	86.40	1222	1858	288.89	0.35	1987	4.58	9,40

Legend: OM = Organic matter; C = carbon; N = nitrogen; P = phosphorus ; K: potassium; CEC = Cation exchange capacity; EC = Electrical conductivity; C/N = Carbon/nitrogen ratio; F0 (95% BVS + 2.50% Ca(OH)₂ + 2.50% zinc); F1 (80% BVS + 2% BP + 15% Clay + 1% Ca(OH)₂ + 2% zinc); F2 (70% DFS + 1.25% BP + 25+% Clay + 1.25% Ca(OH)₂ + 2.50% zinc); F3 (95% DFS + 1% BP + 1% Ca(OH)₂ + 3% zinc); F4 (70% DFS + 1.50% BP + 27.50% Clay + 0.50% Ca(OH)₂ + 0.50% zinc); F5 (80% DFS + 2% BP + 15% Clay + 2.00% Ca(OH)₂ + 1% zinc); F6 (95% DFS + 2% BP + 1.50% Ca(OH)₂ + 1.50% zinc).

Traces metal elements contained in the different formulations

Overall, trace metal element concentrations in the different formulations were found to meet the standard authorized for being used as soil amendment substrates in crop production. As for chromium (Cr), their concentrations were between 17.02 mg kg^− 1 and 28.32 mg kg^− 1, respectively for formulations F3 and F4. Some of the formulations (F0, F3 and F6) had lower contents in Cr than of raw sludge (23.28 mg kg^− 1) (Table 2). Cadmium contents varied between 0.34 and 0.76 mg kg^− 1 for formulations F2 and F1, respectively. The highest copper content (181.3 mg kg^− 1) was observed with formulation F0 and the lowest content (111.2 mg kg^− 1) in formulation F5. As for copper, its concentration in the different formulations was between 111.2 mg kg^− 1 and 181.3 mg kg^− 1, respectively for F5 and F0. Although lower than the authorized agricultural standard, these contents were higher than the ones of raw dry sludge. Nickel contained in the formulations F0, F3 and F6, were 7.49, 6.68 and 7.62 mg kg^− 1, respectively, and lower than the ones of raw sludge (8.42 mg kg^− 1). On the other hand, in the formulations F1, F2, F4 and F5, it was higher than the ones of the raw sludge (8.42 mg kg^− 1). Zinc concentrations remained strictly higher than those of the raw sludge and ranged between 825.7 and 938.6 mg.kg^− 1, respectively for formulations F6 and F0.

Table 4

Trace metal element concentrations in different formulations of organo-mineral amendments and the standards for agricultural uses
	F0	F1	F2	F3	F4	F5	F6	BVS-B	Standard for agricultural use (Brouzes and Chauvière, 2009)
Cr (mg.kg^− 1)	22.22	28.01	37.23	17.02	28.32	25.68	20.76	23.28	70
Cd (mg.kg^− 1)	0.49	0.76	0.34	0.65	0.74	0.58	0.72	0.50	2
Cu (mg.kg^− 1)	181.3	120.7	115.8	162.1	117.1	111.2	132.6	93.89	500
Pb (mg.kg^− 1)	39.67	25.16	21.44	37.25	25.53	21.94	26.59	18.32	200
Ni (mg.kg^− 1)	7.49	9.63	11.52	6.68	9.82	8.50	7.62	8.42	60
Zn (mg.kg^− 1)	938.6	837.0	875.1	786.7	786.4	858.5	825.7	476.70	1200

Legend: BVS-B: Raw Dry faecal sludge ; F0 (95% BVS + 2.50% Ca(OH)₂ + 2.50% zinc); F1 (80% BVS + 2% BP + 15% Clay + 1% Ca(OH)₂ + 2% zinc); F2 (70% BVS + 1.25% BP + 25% Clay + 1.25% Ca(OH)₂ + 2.50% zinc); F3 (95% BVS + 1.00% BP + 1.00% Ca(OH)₂ + 3% zinc); F4 (70% BVS + 1.50% BP + 27.50% Clay + 0.50% Ca(OH)₂ + 0.50% zinc); F5 (80% BVS + 2% BP + 15% Clay + 2% Ca(OH)2 + 1% zinc); F6 (95% BVS + 2% BP + 1.50% Ca(OH)₂ + 1.50% zinc).

Organic matter mineralization as affected by the formulations and soil types

The mineralization rate of the organic matter contained in the different amendment was significantly affected by the type of the formulations as well as by the soil type (Fig. 1).

Legend

F0 (95% DFS + 2.50% Ca(OH) ₂ + 2.50% zinc); F1 (80% DFS + 2% BP + 15% Clay + 1% Ca(OH)₂ + 2% zinc); F2 (70% DFS + 1.25% BP + 25% Clay + 1.25% Ca(OH)₂ + 2.50% zinc); F3 (95% DFS + 1.00% BP + 1.00% Ca(OH)2 + 3% zinc); F4 (70% DFS + 1.50% BP + 27.50% Clay + 0.50% Ca(OH)₂ + 0.50% zinc); F5 (80% DFS + 2% BP + 15% Clay + 2% Ca(OH)₂ + 1% zinc); F6 (95% DFS + 2% BP + 1.50% Ca(OH)₂ + 1.50% zinc); FER (Chromic soil); FLIS (Epipetric Lixisoil); Bars represent mean values (n = 4)

In the Chromic Lixisoils, after burying the « buried bags» for two cropping campaigns (20 months), in formulation F4 (70% DFS + 1.50% BP + 27.50% Clay + 0.50% Ca(OH)₂ + 0.50% zinc), the rate of mineralization of organic matter was reduced by 22.4% and by 62.24% in formulation F0 (95% DFS + 2.50% Ca(OH)₂ + 2.50% zinc), indicating high mineralization of organic matter. As for the « buried bags» in the Epipetric Lixisoils the lowest mineralization rate (31.40 ± 0.14%) was recorded for formulation F4, while F6 (95% DFS + 2% BP + 1.50% Ca(OH)₂ + 1.50% zinc) experienced the highest ones (74.01 ± 0.53%). Regardless of soil type, mineralization of organic matter contained in the different formulations was stronger in the ones without clay. Out of the different substrates added to dry faecal sludge, montmorillonitic clay had the greatest influence on the stabilization of the organic matter in the formulations. Furthermore, whatever the type of formulation, the mineralization of organic matter was greater on the Epipetric Lixisoils compared to the Chromic Lixisoils.

Biochemical parameters as affected by the different formulations

The results highlighted significant differences between different formulations with regard to COD and BOD5 content (p ˂ 0.05) (Table 5). The COD values ranged between 1401.19 ± 46.93 mg l^− 1 and 1921.53 ± 71.09 mg l^− 1, respectively, for fertilizers F0 and F4. These values were lower than the ones recorded in the raw dry faecal sludges (2000.56 ± 12.12 mg l^− 1). Regarding BOD5, the highest value was found in F1 (699.06 ± 90.19 mg l^− 1) while the lowest value (488.65 ± 23. 91) mg l^− 1) was recorded in F5. In general, the values obtained in the different formulations were significantly higher than the ones in the raw dry faecal sludge (399.32 ± 29.03 mg l^− 1). However, the biodegradability ratio (COD/BOD₅) did not show significant differences between the different fertilizers. It varied between 2.24 and 2.72, respectively, for formulation F5 and F1 (Table 3). As for the raw faecal sludge, this ratio was lower than the ones observed for the different formulations, with an average value of 5.00 (Table 3).

Table 5

Biochemical characteristics of various fertilizers
Formulations	DCO (mg.l^− 1)	DBO₅ (mg.l^− 1)	DCO/DBO₅
F0	1401.19 ± 46.93^a	585.12 ± 45.03^a	2.39^a
F1	1903.17 ± 65.96^b	699.06 ± 90.19^b	2.72^a
F2	1430.53 ± 154.3^a	594.38 ± 112.2^a	2.40^a
F3	1623.76 ± 44.22^b	599.53 ± 51.19^a	2.71^a
F4	1921.53 ± 71.09^b	698.70 ± 42.10^b	2.75^a
F5	1542.78 ± 62.32^a	488.65 ± 23.91^c	2.24^a
F6 Raw dry faecal sludge	1451.09 ± 46.17^a 2000.56 ± 12.12^b	576.92 ± 19.17^a 399.32 ± 29.03^d	2.51^a 5.00^b
p-value	0.0076	0.0018	0.012
Significativity	***	***	**

Legend

Means (n = 4) in the same column, with the same letters, are not significantly different at the 5% level.

Pathogenic load of different formulations

Faecal Coliform and Streptococcal contents in different formulations

The fecal coliform and streptococcal loads varied significantly according to the formulation; as well as between the different formulations and the raw faecal sludge (Table 6).

Table 6

Faecal Coliform and Streptococcus contained in the different formulations
Formulations	Number of CF (x 1000 CFU/100ml)	Number of SF (x 10³ CFU /100 ml)	Stands values NFU 44–095 (2011)
F0	19.32 ± 1.56^a	48.25 ± 5.14^a	10⁵ CFU / 100 ml
F1	23.17 ± 1.88^b	49.12 ± 7.27^a
F2	24.35 ± 1.36^b	49.88 ± 2.25^a
F3	23.76 ± 44.22^b	47.35 ± 5.23^a
F4	29.53 ± 1.79^c	52.72 ± 4.15^b
F5	18.78 ± 1.32^a	28.32 ± 3.19^a
F6	28.96 ± 4.16^c	27.29 ± 1.28^a
Raw faecal sludge	32.53 ± 2.87^d	69.11 ± 2.30^c
p-value	0.0018	0.0065
Significatively	***	***
Legend: CF = Faecal Coliforms; CFU = Colony Forming Unit; F0 (95% DFS + 2.50% Ca(OH)₂ + 2.50% zinc); F1 (80% DFS + 2% BP + 15% Clay + 1% Ca(OH)₂ + 2% zinc); F2 (70% DFS + 1.25% BP + 25% Clay + 1.25% Ca(OH)₂ + 2.50% zinc); F3 (95% DFS + 1.00% BP + 1.00% Ca(OH)₂ + 3% zinc); F4 (70% DFS + 1.50% BP + 27.50% Clay + 0.50% Ca(OH)₂ + 0.50% zinc); F5 (80% DFS + 2% BP + 15% Clay + 2% Ca(OH)₂ + 1% zinc); F6 (95% DFS + 2% BP + 1.50% Ca(OH)₂ + 1.50% zinc); ** (p < 0.001)*

Means(n = 4) in the same column, with the same letters, are not significantly different at the 5% level.

The concentrations of faecal coliforms in the raw dry sludge were significantly higher (p < 0.05) compared to the ones of the different formulations (32.53 ± 2.87. 10³ UFC/100 ml). As for the different formulations, their content ranged from 18.78 ± 1.32 10³ UFC/100 ml and 29.53 ± 1.79. 10³ UFC/100 ml. A reduction in the fecal coliform content was observed between the different formulations with increasing dose of slaked lime. The coliform contents, both for the control (raw dry sludge) and the different formulations, met the standard (lower than 105 CFU / 100 ml) for being used as amendment in cereal cropping (Table 6).

for the concentrations of faecal streptococci were highest in the dry faecal sludge (69.11 ± 2.30.103 CFU/100 ml). Among the different formulations, the lowest content of faecal streptococci (27.29 ± 1.28.103 CFU/100 ml) was found in formulation F6, while F2 had the highest content (49.88 ± 2.25.103 CFU/100 ml). The concentration of faecal streptococci was in the range of the stands authorized for agricultural use in dry faecal sludge as well as in the different formulations (Table 6).

Helminth egg concentration in the raw dry faecal sludge and the different formulations

Table 7

Helminth egg contents of different organic fertilizers
Formulations	Helminth egg (/100 g of MS)	Stands values : NFU 44–095 (2011)
F0	2. 15 ± 1.52	5 eggs/100 g MS
F1	3.52 ± 1.53
F2	3.89 ± 0.89
F3	3.72 ± 1.15
F4	3.91 ± 1.17
F5	2.32 ± 0.87
F6	3.35 ± 1.67
Dry faecal sludge	4.12 ± 0.23
p-value	0.0053
Significativity	***

Legend

F0 (95% DFS + 2.50% Ca(OH)2 + 2.50% zinc); F1 (80% DFS + 2% BP + 15% Clay + 1% Ca(OH)2 + 2% zinc); F2 (70% DFS + 1.25% BP + 25% Clay + 1.25% Ca(OH)2 + 2.50% zinc); F3 (95% DFS + 1.00% BP + 1.00% Ca(OH)2 + 3% zinc); F4 (70% DFS + 1.50% BP + 27.50% Clay + 0.50% Ca(OH)2 + 0.50% zinc); F5 (80% DFS + 2% BP + 15% Clay + 2% Ca(OH)2 + 1% zinc); F6 (95% DFS + 2% BP + 1.50% Ca(OH)2 + 1.50% zinc); *** (p < 0.001).

Means (n = 4) in the same column, with the same letters, are not significantly different at the 5% level.

In general, the helminth eggs contained in the different formulations and raw sludge were in the range to be use as fertilizers amendments (< 5 eggs/100 g DM). As for the different formulations, helminth eggs contents varied between 2.15 ± 1.52 eggs/100 g DM and 3.91 ± 0.89 eggs/100 g DM for fertilizers F0 and F4, respectively, corresponding to reductions of 47.81% and 5.10% compared to the raw sludge used as a control (4.12 ± 0.23 eggs/100 g DM). The overall trend of contents of faecal coliforms and streptococci, dropped proportionally the dose of slaked lime (Table 7).

The different organo-mineral amendments (formulations) showed suitable acidity (7.24 < pH < 7.75), for their use as amendments in agricultural soils while the raw dry sludges were too acidic (pH = 4.58). This improvement of the acidity of the formulations compared to raw faecal sludges, can be explained by the nature of the local substrates added to the raw faecal sludges, particularly the slaked lime (Ca(OH)₂) and natural phosphates rock powder. In fact, the slaked lime releases calcium oxide (CaO) which react with the carbonic acid (H₂CO₃) of the faecal sludges and gradually neutralizes the H⁺ ions. These reactions lead to a decrease of the acidity in the formulations that can be recorded by the increase in pH values. Furthermore, the addition of two substrates (phosphate rock powder and slaked lime) as well as that of montmorillonitic clay would have enriched the raw dry faecal sludges in calcium ions (Ca²⁺) leading to a reduction of the acidity in the final substrates (formulations). These results are in line with the ones reported by Strande et al. (2014), who reported the effectiveness of slaked lime in reducing acidity of raw faecal sludge. The different formulations showed fairly high levels of organic carbon. However, for the purpose of being used in agricultural soil amendment, they were more suitable compared to the raw dry faecal sludge. Furthermore, compared to previous studies conducted on dry faecal sludges-based compost combined to solid urban waste by Soré et al. (2021), the formulations of our study had higher nutrient contents.

The C/N trophic balance ratio of the different formulations was found to be higher compared to that of raw sludges. This ratio expresses the mineralization kinetic of organic matter contained in the amendments; in the range of C/N ≤ 10, organic matter contained in the amendments are quickly mineralized and may be lost through lixiviation. All the formulations had a C/N ratio of less than 15, which shows that these formulations are likely to release excess nitrogen for the benefit of the plants, due to the action of the micro-organisms. In fact, we observed fairly high rates of mineralization of organic matter in the various formulations, which indicates their high biodegradability under the action of microorganisms using the nitrogen from these formulations as a source of energy. This could indicate a good synchronization between the N demand for microorganisms’ activities and formulations decomposition (Mareike et al. 2024). Factors such as the diversity of raw materials used for the substrates (formulations), climatic conditions, would have influenced the degradation and humification process in the different formulations tested (Héma et al., 2023).

Trace metal element (TME) contents in the different formulations were lower than those in the raw dry faecal sludges and in the range of the standards for agricultural soil amendment. The complexation of heavy metals by organic matter contained in the raw dry faecal sludge or of humic substances resulting from the mineralization of organic matter may explain why a reduction in the ETM concentration was observed in the different formulations compared to the raw dry sludges. Indeed, the high organic matter contents of raw faecal sludges would have adsorbed heavy metals via humic substances, thus inducing their immobilization by complexation with metal ions (Degbé et al., 2013; Déblon, 2018). Our results are in line with those of Oualid et al. (2022), who reported that the organic fraction of a substrate or fertilizer has a high affinity for metal cations due to the presence of binding agents or functional groups (carboxyls, phenols, alcohols and carbonyls). These functional groups can form complexes with metals. The complexation process of heavy metals is strongly related to substrate acidity. In the study reported herein, the addition of slaked lime to the different formulations led to a reduction of their acidity, favorable to the complexation of metallic trace elements. Indeed, the stability of the complexes formed between cations and ligands increases with the reduction of the acidity and vice versa in the case of anions (Sigg et al., 2000). Christopher et al. (2016), showed that when the environment is basic, the overall charge of the exchangeable site is negative and allows the adsorption of TMEs on the complex. Also, in acidic environments, the overall charge on the solid components surface is positive and adsorption is not possible (Oualid et al., 2022). In addition to its action on reducing the acidity, slaked lime (Ca(OH)₂) gives precipitation reactions with heavy metals giving metal hydroxides (Adeline, 2006), leading to reduction of TMEs concentration. Furthermore, the different formulations that received montmorillonite clay had a low content of trace metal elements which highlights the action of this local substrate on TMEs. According to Sorgho et al. (2011), montmorillonitic clays allow the immobilization of Pb²⁺ and Cr³⁺ ions due to their high specific surface area and complex porous structure. Despite the high organic matter contents of raw dry faecal sludges, their trace metal element contents are higher than those of the different formulations. This confirms that organic matter content is not the only parameter affecting the dynamics of trace metal elements in these organo-mineral amendments.

Regarding the pathogenic loads of the different formulations, they are all suitable for agricultural uses. For the same pathogenic agent, strong variability depending on the formulations were observed while meeting the standards for being us for agricultural soil amendment. The origin and processing methods of dry faecal sludges may explain the low concentration these pathogenic agents. Indeed, according to Héma et al. (2022), the origin of the sludges, their processing and storage conditions after removing it from in the drying beds, reduce their pathogenic loads. They also reported a significant reduction of the concentration of coliforms and streptococci and helminth eggs in dry faecal sludge depending on their storage times. Weather conditions such as temperature, sunshine, and humidity also influence the survival time of these pathogens. Indeed, Schwartzbrod (2003) reported a survival time of one year for Enteroviruses in dehydrated sludge stored at outside temperature compared to 2 years of survival for salmonella from lagoon sludges. Furthermore, the low pathogenic loads in the different formulations could be explained by the intrinsic characteristics of dry sludges, in particular dryness, acidity, the presence of nutrients promoting growth, and biological composition, characteristics which are likely to induce inactivation of pathogens during storage (ADEME, 2007). The influence of the biological composition of the faecal sludges on the dynamics of pathogens is explained by the competition between pathogens and saprophytic organisms of faecal sludges (ADEME, 2007). Overall, viable helminth eggs can normally survive in sludge stored for more than 4 months. Beyond 6 months storage period, there is a reduction in the number of viable eggs (ADEME, 2007). In the current investigation, the dry sludges used were stored for more than six (6) months which may have been the reason for the low concentrations of pathogens, particularly helminth eggs, observed. In hydrated faecal sludge from the Abidjan district, Soro et al. (2020), found 21 ± 18.74 CFU/100mL of helminth eggs which was much higher than those in our study.

As for biochemical properties, the biodegradability ratios of the different formulations were less than 3; indeed, they ranged from 2.24 to 2.79 showing high content of the different formulations in biodegradable and non-biodegraded organic matter. This organic matter can also be regarded as nutrient pool because their progressive mineralization will improve the nutrient reserve for plants and improve soil structure and its structural stability as well. The biodegradability ratio in the raw faecal sludges, on the other hand, ranged between 3.00 and 5.00, contrary to the different formulations, indicating that the raw dry sludges were mineralized sufficiently. Therefore, they can be used as fertilizer because of their nutrient contents but not for soil amendment due to their poor capacity for promoting soil structure and stability.

The investigations conducted by N’Diaye et al. (2018) on the pollutant load of faecal sludges in some sub-Saharan African countries, outlined the key role of the COD/BOD5 ratio on the biodegradability of faecal sludge. According to these authors, a COD/BOD5 ratio less than 2 means the presence of a large proportion of biodegradable substrate and indicates the possibility of biological treatment of sludge. On the other hand, when the biodegradability ratio is above 3, a large part of the organic matter in the sludges is not biodegraded and thus requires a physicochemical purification process for the sludges. Similar results were obtained by Héma et al. (2024) on dry faecal sludge from the drying beds of the Dogona, Kossodo, Sourgoubila and Zagtouli stations in Burkina Faso. They outlined that the dry faecal sludge of the different stations was mineralized enough for farther biological treatment such us composting unless other reasons such us sanitation issues are raised. Compared to the raw dry sludge used as a control, the mineralization of organic matter was less in the different formulations regardless to the soil type. Also, the mineralization rate was lower as the clay content was higher. The addition of montmorillonitic as a binder therefore allowed the stabilization of the organic matter contained in the formulations. Indeed, according to Duchaufour et al. (2018), montmorillonitic clay with 2:1 sheet structure, unlike kaolinite (1:1 type clay), allows building of stable aggregates when associated with organic matter, in the presence of cations such as Ca²⁺ ions. Also, the liming of the dry faecal sludges, in addition to its action on reducing acidity of the different formulations, provides Ca²⁺ ions contributing to calcium bridges formation and stable clay-humic complexes. Regardless of the formulation, a higher mineralization rate was recorded in the Endopetric Lixisoil compared to the chromic Lixisoil. Weather conditions and intrinsic characteristic of these two soils may explain this difference observed. Indeed, important biophysical factors such as soil texture, soil mineralogy, soil structure topography, depth to water table, local climate, and plant diversity can regulate agroecosystem nutrient cycling and influence the dynamics of microbial activities and therefore the mineralization of organic matter (Kate and Rebecca, 2017). CO₂ fluxes depend on soil water content; for optimal water contents, soil pores are approximately half filled with water and air, with water in the micropores and the air in the macropores (Luo and Zhou, 2006). When soil pores are fully filled by water, oxygen diffusion to the microorganisms is no longer optimum (Pauline and Marc, 2010). As for soil textural constitution, it plays an important role of microorganisms´ accessibility to the organic substrates for mineralization (Pauline and Marc, 2010). In particular, clay particles, by binding to organic matter, protect it from enzymatic attacks which reduces its mineralization (Baldock et al. 2000; Huang et al. 2005).

Dry faecal sludge from sanitation systems is a potential source of organic substrates essential for crop production and improving soil quality. However, due to the high acidity and the rapid mineralization of the raw dry faecal sludges, they cannot be used directly. The formulation of different type of dry faecal sludge based organo-mineral amendments, i.e. the association of dry faecal sludge with natural phosphates, montmorillonite and slaked lime, resulted in final amendments (formulations) with high agronomic value and which are safe for the environment and human health. Indeed, compared to the standards, physicochemical, pathogenetic and toxicological parameters of the formulations were improved with the adjunction of these substrates while inducing a reduction in the acidity and mineralization rates of the dry sludge.

Agronomic efficiency was proportional to the quantities of natural phosphates, clay and lime. In the current context of soil amendment product scarcity in the farming systems of subs-Sahelian countries, these formulations are novel perspectives for sustainable soil fertility management while addressing environmental pollution by faecal sludges.

Author Contribution

Author contributions ASH: Conceptualization; Investigation; Methodology; Data curation; Data analysis; Visualization; Drafting. MT: Supervision; Investigation; Resources; Manuscript revision; Fund acquisition. SZ: Investigation; Supervision; Manuscript revision. BK: Methodology; Writing - Reviewing and editing. EI: Methodology; Writing - revising and editing; Formal analysis; Supervision; Data analysis.

Acknowledgements

Authors are indebted to « Office National de l’Eau et de l’Assainissement (ONEA) » and the « Projet d’Appui à l’Enseignement Supérieur (PAES) » for funding the carrent investigations. Our thanks go to the different managers of the dry faecal plants for their kind collaboration during sample collection and all the staff of the laboratory the Institute of Soil Research(IBF)/Department of Forest- and Soil Sciences, University of Natural Resources and Life Sciences, Vienna (BOKU) for hosting part of the laboratory analyses.

ADEME (2007) Scientific basis for assessing health risks associated with pathogens (ADEME Convention: Assessment of health risks associated with wastewater treatment plant sludge spreading systems). Version 1 du 15 Octobre 2007. 172p.
Austrian Standards International (2002) ÖNORM EN 13657: Characterization of waste - Digestion for subsequent determination of aqua regia soluble portion of elements.
Baldock JA, Skjemstad JO (2000) Role of soil matrix and minerals in protecting natural organic materials against biological attack. Org. Geochem., 31, 697–710.
CCNUCC (Convention-cadre des Nations Unies sur les changements climatiques). (2018). Decision 4/CP.23. FCCC/CP/2017/11/Add.1. Disponible au https://undocs.org/en/FCCC/CP/2017/11/)(consulté le 19 Mars 2021)
Christopher MM, William H, Schneider IV, Mufuta JT, Philip C (2016). Winter Maintenance Wash-Water Heavy Metal Removal Pilot Scale Evaluation. Journal of Chemistry, Volume 2016. Available on http://dx.doi.org/10.1155/2016/5347154
Cissé D, Jean-Thomas C, Mamadou T, Fatimata S, Kalifa C, David L, Gilles C, Hassan BN (2021). Co-composted biochar to decrease fertilization rates in cotton–maize rotation in Burkina Faso. Agronomy Journal, 113(6), pp. 5516–5526. DOI: 10.1002/agj2.20867
Déblon J. (2018). Characterization of TME contamination in the Lamping valley (China) and assessment of their bioavailability under different treatments. Master's thesis in bioengineering. Option: environmental sciences and technologies. University of Liège, Liège, Belgium, 132p.
Degbè K, Moursalou K, Sanonka T, Komi E, Essey Z, Dihéénane D, Gado T, Mohamed H. (2013) Study of the competitiveness of complexation of metals from the natural phosphates of Hahotoé-Kpogamé by humic substances. Afrique SCIENCE 09(1): 23–33. ISSN 1813-548X, http://www.afriquescience.info
Duchaufour P, Pierre F, Poulenard J (2018) Introduction to soil science. Soil, vegetation and environment. Dunod Publishing, Paris, France, 472p.
Héma SA, Traoré M, Coulibaly K, Koulibaly B, Nacro HB (2022) Agricultural Soil Fertilizing Potential of Dry Faecal Sludge from Treatment Plants in Burkina Faso. Open Journal of Soil Science. 12, 225–241 https://doi.org/10.4236/ojss.2022.126010
Héma SA, Traoré M, Coulibaly K, Koulibaly B, Nacro HB (2024) Enhancing biodegradability and reducing acidity of dry faecal sludge in arid tropical conditions. International Journal of Development and Sustainability, 12 (11), pp. 546–562
Héma SA, Traoré M, Coulibaly K, Koulibaly B, Yanogo B, Nacro HB (2023) Agronomic efficiency and residual phytotoxicity of organic amendments based on dry faecal sludge and local substrates on maize (Zea mays L.) and cotton (Gossypium herbaceum L.) crops in Burkina Faso. African Journal of Environment and Agriculture, 6(1), 2–11.
Huang PM, Wang MK, Chiu CY (2005) Soil mineral-organic-matter-microbe interactions: impacts on biogeochemical processes and biodiversity in soils. Pedobiologia, 49, 609–635. DOI: 10.1016/j.pedobi.2005.06.006
Ingallinella AM, Sanguinetti G, Koottatep T, Montangero A (2002) The Challenge of Faecal Sludge Management in Urban Areas-Strategies, Regulations and Treatment Options. Water Science and Technology, 46(10): 285–294.
IUSS Working Group WRB, (2015). World reference base for soil resources 2014, Updated 2015. International soil classification system for naming soils and developing soil map legends. World Soil Resources Report No. 106. FAO, Rome.
Kate T, Rebecca R, (2017). Nutrient cycling in agroecosystems: Balancing food and environmental objectives, Agroecology and Sustainable Food Systems, 41(7), 761–798, DOI: 10.1080/21683565.2017.1336149
Koné. M, Emmanuelle S, Yacouba O, Paul O, Lucien BO (2016) Characterization of faecal sludge deposited on the drying beds at Zagtouli (Ouagadougou). Int. J. Biol. Chem. Sci, 10(6), 2781–2795. Available on https://doi.org/https://doi.org/10.4314/ijbcs.v10i6.30
Lo M, Sonko E, hadji M, Dieng D, Ndiaye S, Diop C, Seck A, Gueye A (2020) Co-composting of domestic sewage sludge with market garden waste and fish waste in Dakar (Senegal). Int. J. Biol. Chem. Sci. 13(6): 2914–2929. Available online at http://www.ifgdg.org
Lompo F, Segda Z, Gnankambary Z, Ouandaogo N (2009) Influence of natural phosphates on the quality and biodegradation of corn straw compost. Tropicultura, 27(2): 105–109.
Luo Y., Zhou X. (2006). Soil respiration and the environment. Amsterdam, The Netherlands; Boston, USA: Elsevier Academic Press Inc.
Mareike B, Insa K, Maria E, Vergara H, Gabriele B, Dieter T (2024). Impact of mechanical weed control on soil N dynamics, soil moisture, and crop yield in an organic cropping sequence. Nutr Cycl Agroecosyst 129:223–238. https://doi.org/10.1007/s10705-024-10370-9
Maya C, Torner-Morales FJ, Lucario ES, Hernandez E (2012) Viability of six species of larval and non-larval helminth eggs for different conditions of temperature, pH and dryness. Water Research, 46, 4770–4782. doi: 10.1016/j.watres.2012.06.014.
N'Diaye CM, Boucari H, Sagna M, Touré SC (2018) Characterization of the pollutant load of faecal sludge in Sub-Saharan African countries. Cabinet EDE (“Environment Waste and Water”) International-engineers, consulting, studies and control, 10p.
Nkonya E, Anderson W, Kato E, Koo J, Mirzabaev A, von Braun J, Meyer S (2016) Global cost of land degradation. In: Nkonya, E., Mirzabaev, A., von Braun, J. (Eds.), Economics of Land Degradation and Improvement -A Global Assessment for Sustainable Development. Springer International Publishing, Cham, pp. 117–165.
Oualid MB, Ouarda M, Djamal EA (2022) Enhancement of electrokinetic remediation of lead and copper contaminated soil by combination of multiple modified electrolyte conditioning techniques. Environ. Eng. Res. 27(4): 210–167. https://doi.org/10.4491/eer.2021.167
Pauline B, Marc A (2010) Heterotrophic respiration in agricultural soils: description of important factors and comparison of existing semi-mechanistic models. Biotechnol. Agron. Soc. Environ. 14(4), 707–717
Pouya MB, Savadogo MO, Ouédraogo J, Sermé I, Vognan G, Dakuo D, Sédogo MP, Lompo F (2020) Socio-economic determinants of soil degradation and the adoption of soil fertility management technologies according to farmers' perceptions in the cotton-growing areas of Burkina Faso. Asian Journal of Science and Technology, 11(06):11003–11011. http://www.ijias.issr-journals.org/
Roy AH, McClellian GH (1986) Processing phosphate ores into fertilizers. In Management of nitrogen and phosphorus fertilizers in sub-saharan Africa. Proceedings of a symposium. IFDC, LOME Ed. by Mokwunye and Vlek P.L.G., pp. 244–281.
Sigg L, Behra P, Stumm W (2000) The Chemistry of Aquatic Environments - The Chemistry of Natural Waters and Environmental Interfaces, 3rd Edition, Dunod, Paris, 592 p.
Soil Survey Staff (2004) Soil survey laboratory methods manual. “ Soil Survey Investigations Report 42. (USDA-NRCS: Washington, USA)
Soré OA, Sossou S, Konaté Y, Ouoba S (2021) Valorization by co-composting of dehydrated faecal sludge and organic household solid waste: monitoring and quality. J. Wat. Env. Sci. 5 (1), 616–639.
Sorgho B, Paré S, Guel B, Zerbo L, Traoré K, Persson I (2011) Study of a local clay from Burkina Faso for Cu²⁺, Pb²⁺ and Cr³⁺ decontamination purposes. J. Soc. Ouest-Afr. Chim. (31): 49–59.
Soro G, Coulibaly A, Kouamé SM, Yapo OB, Soro N (2020) Characterization and assessment of the pollutant load of faecal sludge from the district of Abidjan, Southern Côte D'Ivoire. Rev. Ivoir. Sci. Technol. 35, 78–96. SSN 1813–3290, http://www.revist.ci
Strande L, Ronteltap M, Brdjanovic D (2018) Faecal Sludge Management: Systems Approach for Implementation and Operation. (IWA Publishing). 12 Caxton Street London SW1H 0QS, UK: EAWAG/UNESCO-IHE.
Tabatabai MA, Bremner JM (1991) Automated instruments for determination of total carbon, nitrogen, and sulfur in soils by combustion techniques. In„ Soil analysis “(Ed. KA Smith) pp. 261–286. (Marcel Dekker: New York, NY, USA).
Traoré A, Yaméogo LP, Traoré K, Bazongo P, Traoré O (2020) Effect of the single fertilizer formula 23-10-05 + 3.6S + 2.6Mg + 0.3Zn on Barka maize yield in the South Sudan zone of Burkina Faso. Afrique Science, 16(1), 260–270.
WHO (World Health Organization) (1997) Analysis of waste water for recycling in agriculture. Manual of laboratory techniques in parasitology and bacteriology, Geneva. 32 p.
Wuenscher R, Unterfrauner H, Peticzka R, Zehetner F (2015) A comparison of 14 soil phosphorus extraction methods applied to 50 agricultural soils from Central Europe. Plant, Soil and Environment 61, 86–96. DOI: 10.17221/932/2014-PSE

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Enhancing the agronomic value of dry faecal sludge for agricultural soil amendment by adding natural phosphate rock and other local substrates in Burkina Faso

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Abstract

Figures

Introduction

Material and methods

Organic substrate

Additional local substrates used for improving the raw sludges agronomic quality

Formulation of organo-mineral amendments

Physicochemical characterization of organo- mineral amendments

Organic matter mineralization rate in the different formulations

Biochemical characterization of the formulations

Determination of pathogenic load of the different formulations

Bacteriological analysis

N: number of colonies counted

V: volume of inoculum applied to each box

d: dilution factor

Parasitological analysis

N: concentration of helminth eggs

A: number of eggs counted under the microscope

P: capacity of the McMaster blade

X = Volume of zinc sulfate-pellet mixture

Determination of trace metal element contents in the different formulations

Results

Physicochemical characteristics of the formulations

Traces metal elements contained in the different formulations

Organic matter mineralization as affected by the formulations and soil types

Biochemical parameters as affected by the different formulations

Pathogenic load of different formulations

Faecal Coliform and Streptococcal contents in different formulations

Helminth egg concentration in the raw dry faecal sludge and the different formulations

Discussion

Conclusion

Declarations

Author Contribution

Acknowledgements

References

Footnotes

Additional Declarations

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