An equation was developed that quantifies the relationship between volatile solids reduction (VSR) calculated by the Van Kleeck and mass-balance equations. Two sets of data were used to illustrate the significance of fixed-solids loss on the agreement between the two methods. The Van Kleeck equation assumes that fixed solids are conserved during the digestion process; however, this assumption is not needed for the massbalance equation. Therefore, if substantial changes in the fixed-solids concentration occur, the Van Kleeck equation will not be as accurate as the mass-balance equation for computing VSR and will also underestimate VSR. Water Environ. Res., 75, 377 (2003).
A study was conducted to validate test protocols commonly used to assess the stability of various biosolids products and to specify a standard for each test method. A comprehensive and coordinated effort involving a literature review, a selected survey of practicing facilities, and a sampling and analysis program were performed. Information concerning stability testing protocols and data for each of the biosolids stabilization technologies evaluated (aerobic digestion and anaerobic digestion, alkaline stabilization, and composting) and testing methods (specific oxygen uptake rate, volatile solids reduction and additional volatile solids reduction; pH and changes in pH, and carbon dioxide evolution) were collected and evaluated.Specific protocols for each of the five testing methods are recommended. For each of the specific protocols, intrinsic precision data (that is related to the test) are presented. In addition, data are presented from facilities using each protocol to evaluate the collective degree of variability associated with each stabilization process. Using split -sample testing, interlaboratory data (variability among different laboratories) are presented. Issues associated with variability, sources of error, shortcomings and numerical criteria values are discussed for each method.
Prepared for presentation at Water Env ironment Federation Symposia Series, Innov ativ e Uses of Biosolids, September 17 to 19, 2000, Chicago Illinois)
INTRODUCTIONBiosolids management in the future might reveal new processes and management approaches. But the goals will continue to be the same:Decrease quantity of sludge Increase loads on unit processes Improve operation Provide a useful product or byproductDevelop programs that can be implemented and that will lastThe first four goals relate to items that deal with technology. The fifth goal addresses management, rather than technology. These five goals are discussed in turn.
DECREASING QUANTITY OF SLUDGEDecreasing the quantity of sludge to be processed has always been one of the mainstays of sludge processing. For example, thickening, dewatering, drying, and incineration have long decreased sludge volumes. Sludge digestion (aerobic and anaerobic), heat treatment, and incineration decrease the mass of dry solids.There are several options for decreasing production of secondary sludge. Stensel (1999) classifies these methods into four groups:1. Processes that increase the rate of biomass destruction following its synthesis from degradation of substrate;
Innovative Uses of Biosolids
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