Waste Sewage Treatment Research Articles

Sewage sludge drying by energy recovery from OFMSW composting: Preliminary feasibility evaluation

In this paper an original energy recovery method from composting is analyzed. The integrated system exploits the heat available from the aerobic biochemical process in order to support the drying of sewage sludge, using a specific solar greenhouse. The aim is to tackle the problem of organic waste treatment, with specific regard to food waste. This is done by optimizing the energy consumption of the aerobic process of composting, using the heat produced to solve a second important waste management problem such as the sewage waste treatment. Energy and mass balances are presented in a preliminary feasibility study. Referring to a composting plant with a capacity of 15,000t/y of food waste, the estimation of the power from recovered heat for the entire plant resulted about 42kW. The results demonstrated that the energy recoverable can cover part of the heat necessary for the treatment of sludge generated by the population served by the composting plant (in terms of food waste and green waste collection). The addition of a renewable source such as solar energy could cover the residual energy demand. The approach is presented in detail in order for it to be replicated in other case studies or at full scale applications.

Development of a novel, two-step process for treating municipal biosolids for beneficial reuse

Modern municipal sewage waste treatment plants use conventional mechanical and biological processes to reclaim wastewaters. This process has an overall effect of converting a water pollution problem into a solid waste disposal problem (sludges or biosolids). An estimated 10 million tons of biosolids, which require final disposal, are produced annually in the United States. Although numerous disposal options for biosolids are available, including land application, landfilling, and incineration, disposal costs have risen, partly because of increased federal and local environmental restrictions. A novel, thermomechanical biosolids pre-treatment process, which allows for a variety of potential value-added uses, was developed. This two-step process first employs thermal explosive decompression to inactivate or kill the microbial cells and viruses. This primary step also results in the rupture of a small amount of the microbial biomass and increases the intrinsic fluidity of the biosolids. The second step uses shear to effect a near-complete rupturing of the microbial biomass, and shears the nondigested organics, which increases the overall surface area. Pretreated biosolids may be subjected to a secondary anaerobic digestion process to produce additional fuel gas, and to provide for a high-quality, easily dewatered compost product. This novel biosolids pretreatment process was recently allowed a United States patent.

Aerobic biometer analysis of glucose and starch biodegradation

The ASTM D5210-91 protocol for evaluating the biodegradability of a polymer was examined. The reactor design was modified not only to account for the total CO2 evolved but also to allow for the simultaneous carbon assessment in microbes, soluble products, and solid samples. Improvements in the test procedure were implemented such as (1) refining the CO2 pretrap and posttrap design, (2) optimizing the carbon dioxide removal efficiency, (3) accounting for the total polymeric carbon, (4) standardizing the inoculum, and (5) revising the nutrient medium. By growing the sludge on a suitable substrate prior to polymeric exposure, a constant microbial density was obtained. The modified ASTM method provides an assessment of the polymeric carbon degradation at any given time. The results of this work have specific significance to the behavior of polymers in a sewage waste treatment plant, where sludge is continuously being acrated, and also for aerobic biodegradation in general.