Northeastern Biochar utilizes proven and proprietary thermal treatment technology process to dehydrate and treat biosolid waste materials in an environmentally safe way.
Today in North America, the most common practices for further treatment and/or disposal of municipal sewage sludges include the following:
While some of these methods are better than others in terms of safe handling, further treatment and disposal, none are as safe, viable and useful as dehydration and thermal treatment. Here’s why.
Anaerobic digestion (AE)
Anaerobic Digestion (ae) is a common approach for sludge treatment in the wastewater management industry today and has actually been deployed since the early 1900s. The primary goal of this practice is to reduce the total volume of sludge requiring ultimate disposal. With anaerobic digestion, much of the organic matter is broken down into carbon dioxide and methane in an oxygen starved environment. About half of the sludge volume is thereby converted into gases, while the balance is dried into the form of a residual, soil-like material. When properly designed as an onsite component of a wastewater treatment system, the methane gas produced by this method can offset some of the energy needed to run the facility, and/or it can be contained and transported for use elsewhere. This is referred to as “co-generation.” Sounds fine – what is wrong with AE?
- Very expensive in comparison to dehydration and thermal treatment.
- Still produces waste, although properly digested “clean” sludge can and often is used as a viable fertilizer and is mostly devoid of pathogens but still contains dangerous compounds that are not broken down within the process.
- The most common problems associated with industrial grade anaerobic digestion systems are Foaming, Acidification, Increasing Viscosity and/or VFA and TIC Values, and Low Methane Yield. These problems can be avoided by experienced, qualified operators of advanced, technologically sound and modern systems, yet can cause catastrophic plant failures and/or extended system downtime when not carefully and expertly designed and managed. Bottom line, these systems are complicated and have very high design, construction and operating costs.
Direct agricultural application as fertilizer
Applying municipal sewage sludge directly to agricultural fields as fertilizer is not a soil or human health conscious or environmentally friendly practice, but happens extensively, nonetheless. Sewage sludge contains many dangerous compounds including such things as flame retardants, heavy metals, polycyclic aromatic hydrocarbons, dioxins, phthalates, pharmaceuticals and many other chemicals and organisms. The U.S. government regulates about 10 of the thousands of nasty contaminants found in sewage sludge (fecal coliform plus nine heavy metals). Society should be aware of and consider carefully the use of such materials directly on farm fields growing food crops. Moreover, as with any fertilizer spread directly on farm fields, components of the fertilizer product invariably end up in surface and groundwater in the natural process of water transport during and following rain events. Perhaps the most visible and obvious side effect can be readily seen in the form of thick algae blooms in nearby retention or natural ponds. The algae population explodes when introduced to the inflowing nutrients – one must acknowledge that macro nutrients are not the only substances entering the water body.
Composting is an aerobic process of mixing sewage sludge with agricultural byproduct sources of carbon such as sawdust, straw or wood chips. While composting is a cost effective means to kill pathogens in the source material, it does not provide a level of thermal treatment sufficient to breakdown dangerous compounds found in sewage sludge. However, it surely does produce a nuisance odor that you would not want to live near, along with atmospheric release of methane gas and CO2 and the potential for spontaneous combustion if compost piles are mismanaged and allowed to overheat. Indoor composting is a novel concept that is growing in practice and scale, whereby nuisance odor can be managed through the use of an air treatment system.