Loubna El Fels

Study of Humic Acids during Composting of Ligno-Cellulose Waste by Infra-Red Spectroscopic and Thermogravimetric/Thermal Differential Analysis

ABSTRACT Infra-red spectroscopy (FTIR) and thermogravimetric and differential thermal analysis (TGA/DTA) were used to characterize the chemical structure of the humic acids (HA) extracted from two composts of date palm waste: in one the date palm waste was alone (DPW) and in the other, it was mixed with couch-grass clippings (DPCG). FTIR showed that the HA of both origins were rich in aromatic and phenolic structures indicating the presence of lignin degradation products. Both aliphatic and aromatic components were found in the HA. The persistence of certain aliphatic structures resistant to degradation was equally observed. For the DPCG mixture, the HA formed had a structure richer in peptides and carboxylic compounds than DPW compost, which was richer in aliphatic compounds. We can deduce that the DPCG mixture reached greater maturity than the DPW compost. The IR absorption ratios did not show the same patterns of change during the gradual degradation of substrate occurring on composting. Underlying the variations specific to each compost was a different degree of humification. It was higher for the DPCG mixture. FTIR results confirmed those of TDA/TGA thermal analysis, again showing the aliphatic and aromatic character of HA. The RTDA ratio stresses that functionalization of organic matter was more marked than its aromatization.

Biodegradation of organic compounds during co-composting of olive oil mill waste and municipal solid waste with added rock phosphate

Liquid and solid olive oil mill waste was treated by composting in a mixture with the organic part of municipal solid waste and rock phosphate. The transformations that occurred during the process were evaluated by physical, chemical and spectroscopic analyses. After five months of composting, the final compost presented a C/N ratio under 20, an ratio under 1 and a pH around neutral. A high level of organic matter decomposition paralleled a notable abatement of phenols and lipids. The results show the effective dissolution of mineral elements during composting. This transformation was followed by Fourier transform infrared which showed a decrease in the absorption bands of aliphatic bonds (2925 and 2855 cm−1) and carbonyls of carboxylic origin (1740 cm−1). In addition to the increase in humic substances and the improvement of germination indices, the parameters studied confirm the stability and the maturity of the composts. The absence of phytotoxicity opens the way to agricultural spreading.

Artemia salina as a new index for assessment of acute cytotoxicity during co-composting of sewage sludge and lignocellulose waste.

Considering the necessity to constantly monitor the safety of use of sewage sludge, we have focused on evaluating the toxicity of raw sludge and sludge treated by co-composting with date palm waste using an in vitro assessment of cytotoxicity based on Artemia salina larvae as a simple new sensitive and reliable routine test. The efficiency of co-composting in decreasing sludge toxicity was evaluated in terms of cytotoxicity abatement reaching 100% by the second month of composting for mixture A (1/3 sludge+2/3 date palm waste) and the third month for mixture B (1/2 sludge+1/2 date palm waste). Cytotoxicity abatement was confirmed by the increase of germination index, which reached over 100% with positive correlation for lettuce (R(2)=0.81 and 0.86) and for turnip (R(2)=0.87 and 0.74) for mixtures A and B respectively. A strong correlation between the proposed cytotoxicity test and the evolution of regulatory physical-chemical approaches was found, (R(2)=0.88 and 0.89) for NH4(+)/NO3(-) and (R(2)=0.80 and 0.88) for C/N respectively for mixture A and B. These findings allow the inexpensive bioassay reported to be used as a highly sensitive test to determine the cytotoxicity and maturity of composts.

Two culture approaches used to determine the co-composting stages by assess of the total microflora changes during sewage sludge and date palm waste co-composting

Indigenous microflora community changes during six months of co-composting of activated sewage sludge and date palm waste was investigated using two different culture approaches. In order to evaluate the co-composting process evolution for mixture A and B, growth standard media (GSM) and Compost Time Extract Agar (CTEA) are used. Enumeration for indigenous flora abundance on GSM medium shows that the colony-forming unit (CFU) total number was 100 fold higher than on CTEA. The thermophilic phase is determined at 30 day for both mixtures A and B. Nevertheless this stage is limited only at 22 and 30 days, respectively for mixture A and B on CTEA medium, which indicate a similar temperature profile at versus time of co-composting.The results suggest that the GSM medium approach can be used for monitoring the microbial cultivable presence. However, CTEA act as a natural selective medium to enumerate the indigenous functional microflora. This technique was successful in assessing the process evolution and determination of a real succession thermophilic and maturation co-composting stages.

Date palm and the activated sludge co-composting actinobacteria sanitization potential

The objective of this study was to find a connection between the development of the compost actinobacteria and the potential involvement of antagonistic thermophilic actinomycetes in compost sanitization as high temperature additional role. An abundance of actinobacteria and coliforms during the activated sludge and date palm co-composting is determined. Hundred actinomycete isolates were isolated from the sample collected at different composting times. To evaluate the antagonistic effects of the different recovered actinomycete isolates, several wastewater-linked microorganisms known as human and plant potential pathogens were used. The results showed that 12 isolates have an in vitro inhibitory effect on at least 9 of the indicator microorganisms while only 4 active strains inhibit all these pathogens. The antimicrobial activities of sterilized composting time extracts are also investigated.

Advantages and Limitations of Using FTIR Spectroscopy for Assessing the Maturity of Sewage Sludge and Olive Oil Waste Co-composts

Composts prepared using different solid and liquid organic wastes from various sources can be used as growing media when these materials present adequate proprieties for plant development. The stability and maturity are among the main characteristics of composts. The purpose of this study is to recommend specific bands of the IR spectrum recorded on different composts to enable qualitative and rapid monitoring of the stages of biodegradation during composting. At the beginning of humification, the significant decrease in the intensity of the band located at 1735 cm– 1 shows that lignin is affected at the first stage of the composting process. At the end of the humification, the band located toward 3450–3420 cm–1 at the beginning of the process undergoes a systematic shift (Δν of the order of 10 cm–1) toward lower wave numbers. The band located at 1660–1650 cm–1 on the Fourier transform infrared spectroscopy (FTIR) spectra before composting shifts systematically toward 1640 cm–1 at the end of humification. This phenomenon can be used as index of compost maturity. Measuring the band at 1035 cm–1 as an internal standard, it is possible to quantify the degradation rate of organic matter.

Use of the co-composting time extract agar to evaluate the microbial community changes during the co-composting of activated sludge and date palm waste

This study investigates changes in the microbiological community of two co-composting mixtures of activated sludge and date palm waste over a 6-month period. The use of the co-composting time extract medium to evaluate the abundance of cultivable indigenous microflora showed that the total microbial biomass was higher during the thermophilic phase. The mesophilic microflora was more abundant than the thermophilic bacteria, throughout the co-composting process. The proportion of mesophilic and thermophilic actinobacteria was high during the maturation phase especially for mixture A. However, thermotolerant fungal microflora increased during the thermophilic stage. Furthermore, correlating physico-chemical analysis of samples with bacterial diversity indicated that the bacterial communities underwent temperature changes. Enterococci and thermotolerant coliforms decreased significantly toward the end of the co-composting process which indicates the safety and sanitization of the end product.

Human and veterinary antibiotics during composting of sludge or manure: Global perspectives on persistence, degradation, and resistance genes

Wastewater treatment plant effluent, sludge and manure are the main sources of contamination by antibiotics in the whole environment compartments (soil, sediment, surface and underground water). One of the major consequences of the antibiotics discharge into the environment could be the prevalence of a bacterial resistance to antibiotic. In this review, four groups of antibiotics (Tetracyclines, Fluoroquinolones, Macrolides and Sulfonamides) were focused for the background on their wide spread occurrence in sludge and manure and for their effects on several target and non-target species. The antibiotics concentrations range between 1 and 136,000 μg kg-1 of dry matter in sludge and manure, representing a potential risk for the human health and the environment. Composting of sludge or manure is a well-known and used organic matter stabilization technology, which could be effective in reducing the antibiotics levels as well as the antibiotic resistance genes. During sludge or manure composting, the antibiotics removals range between 17-100%. The deduced calculated half-lives range between 1-105 days for most of the studied antibiotics. Nevertheless, these removals are often based on the measurement of concentration without considering the matter removal (lack of matter balance) and very few studies are emphasized on the removal mechanisms (biotic/abiotic, bound residues formation) and the potential presence of more or less hazardous transformation products. The results from the few studies on the fate of the antibiotic resistance genes during sludge or manure composting are still inconsistent showing either decrease or increase of their concentration in the final product. Whether for antibiotic or antibiotic resistance genes, additional researches are needed, gathering chemical, microbiological and toxicological data to better understand the implied removal mechanisms (chemical, physical and biological), the interactions between both components and the environmental matrices (organic, inorganic bearing phases) and how composting process could be optimized to reduce the discharge of antibiotics and antibiotic resistance genes into the environment.

Assessment of Biotransformation of Sludge from Vegetable Oil Refining by Composting

ABSTRACT The evolution of organic matter of sludge from vegetable oil refining (50%) mixed with turf (40%) and straw (10%) during 6 months of composting was evaluated by physicochemical and spectroscopy analysis. The intense microbial activity is characterized by a significant increase in temperature (over 67°C) during the thermophilic phase (7 days). The final product is characterized by a decomposition rate of 50, C/N ratio about 12, NH4+/NO3− ratio less than 1, and a neutral pH. The lipid analysis showed that total lipids decreased by 83% as a result of biodegradation of lipid compounds of the composted substrate. The degree of polymerization during composting is of about 16%, which provides information on the success of the process. The spectroscopic analysis showed a decrease of the ratios E4/E6 and E2/E6, which clearly shows the humification of organic matter. The physicochemical and spectroscopy parameters of the mixture show the stability and maturity of the final compost, which is confirmed by the germination index (60% for lettuce and turnips, and 90% for cress and lucerna). The results of the evolution of sludge from vegetable oil refining mixed with green wastes produced a mature product that can be applied in agriculture.

Assessment of Biodegradation of Oleandrin during Co-composting of Nerium oleander L. Wastes

ABSTRACT Variations in the levels of the highly toxic oleandrin molecules were studied during composting of Nerium oleander L. waste mixed with clippings of the grass Pennisetum clandistenum L. The thermophilic phase is characterized by a rise in temperature, which reached 70°C. After 150 days of co-composting, the C/N ratio was 11, the pH was 8, the NO3−/NH4+ ratio was greater than 1 and overall decomposition reached 70%. During the successive stages of co-composting, oleandrin concentrations were monitored by HPLC. The relative abundance of oleadrin was 26.84% at T0 with 10% abatement during the first month and 90% after two months (stabilization phase), reaching 100%, i.e., total removal after 90 days of co-composting (maturation phase). The biodegradation of the toxic substance was largely attributed to the activity of actinomycetes and fungi. The germination index of lettuce and watercress seeds exceeded 50% after 90 days and reached 95% after 150 days, confirming that the final compost was mature, stable, and free from phytotoxicity in spite of the highly poisonous starting material.