Introduction
The treatment of domestic and city garbage presents several problems in its treatment. On the one hand, the organic decomposition process and the formation of leachates that contaminate the soil and the water tables when these wastes are taken to landfills. The case study in this presentation is the laboratory research regarding the contamination of RSU leachates and therefore the concern to mitigate the impact through alternatives for the use of copper salts, since interesting results were found in RSU deposited having a base of copper sulfate. This research is based on the work carried out by Professor William Keevil, from the University of Southampton, who experimented with copper for medicinal purposes,in this case it is presented for the treatment of RSU leachates.
objective
Investigate treatment alternatives with copper for MSW leachates and reduce their environmental contamination.
Conceptual framework
Experimentally, there are already works, such as that carried out by Professor William Keevil, from the University of Southampton, who carried out experiments to show the antimicrobial efficacy of copper as a material for contact surfaces, his experiments can be seen on the page: https: / /www.ncbi.nlm.nih.gov/pmc/articles/PMC5457048/. The experiment demonstrates the effectiveness of copper surfaces in preventing infectious diseases caused by pathogenic microorganisms, as well as their role in combating antimicrobial resistance. In hospital practice, it is common to find that the doorknobs or door handles are made of copper, and that they show their antimicrobial power through an ionization characteristic, and that together with the morphology of bacteria, microbes and viruses, it allows to stop and destroy microorganisms.
One of the properties or applications of copper that is gaining the interest of the scientific community in recent times is its use as a biocidal agent. Studies to explain and apply the use of this metal as a microbicide have been significantly increased, although the potential ability of copper ions, either alone or in copper complexes, to remove microbial contaminants was known and appreciated long before by various Civilizations. In other applications: In the seventeenth century copper was also used in agriculture since it was observed that when washing the seeds with copper sulfate solutions, this element had a powerful fungicidal action. Currently many plant pests are tempered or attacked with fungicides and disinfectants based on copper salts such as sulfates, oxychlorides, etc.
Copper and its inhibitory or bactericidal property will also depend on its concentration. Depending on the microorganism, copper can act as a bacteriostatic agent –which inhibits its growth or multiplication, or as a bactericide, -which eliminates the microorganism. As mechanisms to explain their behavior we have 3 basic causes.
- Inhibits or alters protein synthesis (bacteriostatic activity) Alters the permeability of the cell membrane of microorganisms causing per oxidation, which is oxidative damage to lipids, which are the key to the exchange of molecules from the intracellular to the extracellular environment and vice versa (bactericidal activity) Copper destroys or alters the nucleic acids (DNA) of bacteria and viruses, but it is not mutagenic. The ability to multiply is lost (bactericidal property).
The following results were evaluated at the Medical University of South Carolina for the antimicrobial efficacy of copper.
Copper reduces the average number of microbes by 97%. Virtually no MRSA or VRE are found on copper surfaces. The reduction of microbial load on copper surfaces continuously reaches the same levels as terminal cleaning. The deployment of copper surfaces led to a 40-70% reduction in infection rates. The antimicrobial activity of copper is continuous - (works non-stop and all day)
Development
This research project was carried out at UPIICSA (Interdisciplinary Professional Unit of Engineering and Social and Administrative Sciences). For which it began with bibliographic research, later laboratory research and consists mainly of two parts:
1st part. Repeating experiment by William Keevil.- to check the inhibition of bacteria by copper.
2nd part. Experimental research with cans for domestic garbage with a capacity of 17 liters.
1st part. Repeat experiment of William Keevil.
With equipment limitations, small changes were made to the experiment, such as the sample size. To carry out the experiment, two effects on different materials are compared; a copper plate and a steel plate, 1 approx. 8 cm per side and a thickness of 1 mm (Keevil made it with plates around 30 cm)
Each of the plates was placed in a Petri dish respectively, in order to avoid the spread of bacteria. About 1 ml of a liquid containing bacteria donated by the microbiology laboratory of the Faculty of Chemistry of UNAM, which contained staphylococcus gold resistant to penicillin, were deposited on each plate. These culture bacteria were stained with a green fluorescent bacterial indicator dye to make it visible under the microscope.
As the microorganisms disappear, the fluorescence will decrease. The rate of decline in fluorescence will indicate the antimicrobial potency of the surface on which it has been placed. Rapid fading means that surface has powerful antimicrobial potency.
After 8 minutes on the copper plate a great decrease in fluorescence was observed and on the steel plate the staining continued. Proving in this way the antifungal and antimicrobial power of Copper.
(It is important to note that due to the limitations in the microbiology equipment at UPIICSA, the experimentation was carried out with the support of laboratories at the UNAM Faculty of Chemistry, and a methodology to validate these primary results, which are very encouraging, must be considered under the design of experiments. Well, it has to be verified with different strains according to the literature).
2nd part. Experimental research with cans for domestic garbage with a capacity of 17 liters.
The investigation consisted of doing two types of tests; For the first test, 3 types of experiments were carried out, which were carried out in triplicate in each case, and consisted of experimenting with household garbage containers using copper sulfate, copper oxides and copper shavings as filtering media:
The first experiment consisted of collecting 5 kg of homemade organic waste: lettuce, carrot, tomato, cabbage, beef, avocado, melon, peach, chicken bone, watermelon, papaya, beans, egg, potato, which are left to ferment. 7 days. During this fermentation the residues contained in the containers are pressed and covered so that external insects do not intervene to the process that could bring pathogens.
These organic residues were deposited in a 17-liter pot which contained 0.5 cm diameter perforations in the bottom, (15 holes), and a 5 cm layer of copper sulfate.
The second experiment consisted of depositing copper oxides at the bottom of the container in which the fermentation of the organic residues was carried out and with the same characteristics as in the first.
The third experiment under the same conditions as the previous ones except for the filter medium, which in this case copper chip was used
In all cases, observations were made and the amount of resulting microorganisms was analyzed by the microbiology laboratory of the UNAM's chemistry faculty, with a decrease of up to 95% after passing the filtering. The microorganisms were Alternaria, Aspergillus, Botrytis fungi, in no case were heavy metals or pathogenic microorganisms such as coliforms or salmonella found.
Initially, a test was run without any type of treatment, that is, the leachate was collected and sent for analysis to find out the amount and type of bacteria or microorganisms, later the comparative calculation was carried out in each of the cases.
Results
- In relation to microorganisms and fungi contained in organic waste: Leachates filtered by copper shavings decreased by approximately 99%. In other words, the fungi and microorganisms almost disappeared. Leachates filtered by copper sulfate decreased by approximately 80%. Leachates filtered by copper oxide decreased by approximately 80%. In no case did coliforms or pathogens such as Staphylococus bacteria or Salmonella: Copper and its derivatives such as copper sulfate, oxides, have a high antifungal, antimicrobial, and disinfectant power.
Conclusions
Copper can be used to reduce the contamination of organic waste leachates, so it would be ideal for use in sanitary landfills, it is recommended to previously treat the waste deposit with a layer of copper shavings or filings, or with copper sulfate., where Cu2 + acts as a strong oxidant due to its ionizing power, inhibiting or killing undesirable microorganisms that can contaminate the water table.
References
- Negroni Marta Microbiología (2009) Stomatológica Mex 2ª. Edn., Ed. Médica.Panamericana, Buenos Aires Argentina 9500615843, 9789500615846.Michels, MG Schmidt. October 2008. A Pilot Study to Determine the Effectiveness of Copper in Reducing the Microbial Burden (MB) of Objects in Rooms of Intensive Care Unit (ICU) Patients, CD Salgado, A Morgan, KA Sepkowitz, JF John, JR Cantey, HH Attaway, T Plaskett, LL Steed, HT Michels, MG Schmidt. Poster 183, 5th Decennial International Conference on Healthcare- Associated Infections, Atlanta, March 29, 2010 BJ and R. Gómez (1995), Environmental education: recycling and recovery of household waste, Madrid: UNED.SEDESOL (Social Development Secretariat of México) (2005), The Management of Urban Solid Waste and Special Management in México, México: Sancho y Cervera, J. - Rosiles, G.
