Watcharapol Chayaprasert

Evaluating the Effects of Sealing Quality on Gas Leakage Rates During Structural Fumigation by Pressurization Testing and CFD Simulations

In this study, pressurization tests were conducted to quantify gas-tightness of the Hal Ross Flour Mill at Kansas State University, which was sealed at three sealing qualities, i.e., fully sealed, partially sealed, and non-sealed. A computational fluid dynamics (CFD) model of the mill was then constructed. Based on the building gas-tightness levels obtained from the pressurization tests, several sulfuryl fluoride fumigations were simulated to study sensitivities of the half-loss time (HLT) and concentration × time (Ct) product of the mill as affected by sealing quality, and wind and buoyancy forces. The HLT of the fully sealed simulation case was at least two to three times greater than that of the partially and non-sealed cases, respectively. The Ct product results followed a similar trend. The results of this study emphasized the importance of the pressurization test as a useful tool for quantification of building gas-tightness and for prediction of expected HLT and Ct product of a subsequent structural fumigation.

Composting of biodegradable organic waste from Thai household in a semi-continuous composter

ABSTRACT An 80-L prototype of a home composter was designed to be possibly applied in households with 4–6 members. Biodegradable waste generation was assumed to be 1–2 kg d−1. The composter consisted of a waste chamber, a pair of 12-cm diameter aeration fans, and an agitator. Five experiments with various feeding rates, mixing frequencies, and composting periods were conducted using a semi-continuous compost process under partially aerobic conditions. Tested were a feeding rate of 1 or 2 kg d−1 and a stirring frequency of 12 or 24 times d−1, the organic content of the compost was 58%–78%, and total nitrogen, phosphorus, and potassium were 1.3%–1.9%, 0.1%–0.2%, and 0.5%–1.0%, respectively. The compost was dark brown and odorless. The compost all passed a 12.5-mm mesh, while over 85% passed a 2-mm mesh. It is suggested that with a feeding rate of 1–2 kg d−1 the composting period should be 30 d. If the composting period has to be as short as 15 d, the feeding rate should be only 1 kg d−1.