The most promising and environmentally friendly method of sludge processing is the process of agents application, which are based on humic and fulvic acids.
Industrialization and the increase in the number of settlements has caused a significant increase in impact on the atmosphere, soil, surface and groundwater. This is fully applied to such an area of municipal economy as pollution control facilities. As a rule, treatment and filtering stations are evaluated as facilities worth increased environmental attention. In these cases, integrated solutions are needed.
What harm do sludge fields cause to the city
Sludge fields are a complex multicomponent system consisting of organic and mineral parts. Wastes in the form of sludge after the treatment of waste water residues are a big problem for cities for two reasons:
- Technical aspect. These are large areas occupied by wastewater treating facilities, until recently the absence of reliable technologies that would completely neutralize wastes and recycle them into products useful to humans.
- Socio-environmental aspect. These are stinking odors and environmental degradation near such enterprises.
Therefore, the most important environmental challenge is the safe return of products generated during the processing of human wastes to the environment.
Sludge disposal problem solutions
The sewage sludge disposal at landfills and placement on silt detention ponds continues to be a traditional way to neutralize them. This does not make economic and environmental sense for several reasons:
- Significant funds are spent for dewatering and removal of sludge, as well as for the use of landfills.
- The environmental hazard remains, as the toxins contained in the sediments are not completely localized at the burial site and gradually spread to nearby territories with melt and groundwater.
- Sticking odor of organic matter, the presence of heavy metals and dangerous microorganisms (helminths).
- Extremely high tensile strength, reaching a value of about 109 dyne/cm2, which corresponds to some steel types by this indicator.
Our studies over the past 3 years have shown that the most promising and environmentally friendly method of sludge processing is the process of agents application, which are based on humic and fulvic acids. These natural compounds are capable of destroying organic components resistant to oxidation at the molecular level, as well as binding heavy metals into stable non-toxic complexes that will meet sanitary and hygienic requirements.
The preliminary results obtained from of sludge disinfection tests using AViTA® brand agents showed worthy results. This confirms the need to continue efforts to intensify the processes of pre-treatment and disinfection of waste generated. Their processing into high-quality organic mixtures used for soil remediation and landscape use in forest-park areas is an additional advantage.
The tasks, which we managed to solve:
- sticking odor stopping in 7-14 days;
- sludge volume 3 times decrease;
- coli titer values improvement (E. coli content);
- dehelminthization and sludge safety;
- binding of heavy metals to stable non-toxic complexes;
- the possibility of using sludge sediment as a safe soil.
Sludge processing and deactivation technology
Stage 1:
Deactivation of pathogenic microorganisms contained in the sludge using enzyme agents of the AViTA® brand occurs in two possible variants:
- After the dehydration process of the water-sludge mixture on the press filters to 45-55% of moisture content by spraying. The solution is fed through a nozzle into the working chamber of the press filter, where the sludge mixture is processed during mixing.
- During the sludge transportation to storage cells. This option provides for the use of standard equipment of the enterprise (front-end loader or excavator) for equable mixing.
Stage 2:
Along with a simultaneous application of AViTA® brand agents, heavy metals are also neutralized and toxins contained in the sludge are bound. This is the most promising and sufficiently investigated process. Humic acid is the basis of the agent, which is characterized by saturation with various functional groups, increased reactivity during reductive-oxidative and complexing processes. When interacting with heavy metals, insoluble salts are formed that cannot penetrate either the soil or the plants.
The sludge deactivation with a humic agent eliminates the negative impact of heavy metals and allows the use of sludge as the basis of artificial soils and manures in agriculture.
Optimal doses of the agent should be selected by pH-metric titration method (up to pH 8-8.5). In this case, 100% binding of heavy metals to insoluble, stable, long molecular chains occurs, and complexes inaccessible for absorption by soils and plants are created. The effect of the humic agents dose on the heavy metals concentration in an aqueous solution is provided in the chart.
Stage 3:
Bioremediation is the transition from a sterile and inanimate substrate to a valuable product enriched with beneficial microflora - compost.
Sludge treatment with AViTA® at sludge lagoons and silt detention ponds is recommended to be performed throughout the year. Its operation time (for stopping the sticking odor, dehelminthization and binding of heavy metals) is only a few minutes. When using other technologies, it takes several days to achieve the same result.
But in view of the fact that the agent is made of natural components, its effect on the native microflora occurs at positive temperatures not lower than +5 С°. Otherwise, all microorganisms involved in the bioconversion process are in suspended animation, and biological processes stop. At temperatures above +5 C°, the bioconversion process resumes.
The sludge obtained as a result of processing (organomineral composition) is:
- Non toxic.
- Does not contain pathogenic microflora.
- Rich in microelements.
- Contains nitrogen and phosphorus.
This makes it attractive for use as an organic mixture for soil remediation in the forest area.
The technology for processing and composting the treated sewage sludge of urban wastewater treatment plants with AViTA® enzyme agent is very effective, which is confirmed by the studies. It allows environmentally safe and cost-effective solution to the problem of sludge disposal, returning them to the biogeochemical cycle.