Development of Heat-dried Biosolids Product for Application in the Wetlands

In this paper, ferrate and ferric chloride were added to New Orleans municipal sludge in the dewatering step before heat drying. The study noted that ferrate was instable in the sludge cake, which has been substantiated by the deactivation EDCs and disinfection of New Orleans wastewater effluent going to the wetlands. For this study, the optimum dosage for ferric chloride was observed to be 2.3% iron/total solids (TS) of sludge by weight.The iron treated heat-dried biosolids inhibits putrefaction for over 5 to 6 days under a worst-case scenario (moisture content of 98 to 99% and seeded with microbes). The heat-dried biosolids inactivated vegetative microbes since it simulates pasteurization. Therefore, this ferric chloride could resist the putrefication process for over 2 to 3 weeks. The rationale for inhibition is that the iron addition will buffer the ORP with an electron pke similar to an acid/base reaction, and the ferric hydroxide has a high affinity to react with the sulfide and thiocompounds to reduce odor emission. The usage of ferrous and ferric salts has been used in for over the last 20 years in controlling odors in collection systems.In addition, ferrate and ferric salts have a high affinity for sulfur compound or functional groups as noted in the literature. The EDC activity of the heat-dried biosolids and E-beam treated biosolids appears to be lower than that in the sludge cake and puts its activity similar to those in wetland sediment as a result of ferrate and ferric hydroxide addition.