Volatile fatty acids production from fermentation of secondary sewage sludge : a thesis presented in partial fulfillment of the requirements for the degree of Master of Engineering in Environmental Engineering

Sludge fermentation is used worldwide as an economical means to produce volatile fatty acids (VFA), which can be used as readily available carbon in biological nutrient removal (BNR) systems. In this research, secondary sludge was tested for its potential to generate VFA. Fermentation of secondary sludge was carried out in a lab-scale sequencing batch reactor (SBR). The SBR was fed with secondary sludge of 1% total solids and run with hydraulic retention time (HRT) of 48 hours and 28 hours in phase 1 (40 days) and phase 2 (12 days) respectively. The SBR produced net VFA (expressed as acetic acid) of 365 ±62.5 mg VFA HAC /I which was equivalent to a VFA yield of 0.28 ±0.05 mg VFA HAC /mg VSS feed during phase 1. A change in operating HRT from 48 hours to 28 hours led to a reduction in solids retention time (SRT) from 2.65 days to 2 days in phase 2. The reduction in SRT during phase 2 led to poor hydrolysis and hence could not support the fermentation. Net VFA generation decreased during phase 2 and reached 0 mg/I. Acetic acid was the main acid produced comprising 45% of total VFA content during the run with 48 hours HRT. The effect of total solids (TS) concentration on secondary sludge fermentation was tested using batch experiments. The batch with 2.8% TS secondary sludge showed a maximum net VFA production of 60 mg VFA HAC /I, which appeared to be superior to the 1% TS secondary sludge batch fermentation where no net VFA production observed throughout the test period. Primary sludge (3% TS) exhibited 1200 mg VFA HAC /I in a batch fermentation, which was superior to the net VFA produced during secondary sludge (2.8% TS) batch fermentation. The effects of sonication on fermentability of primary and secondary sludges were tested. A sonic power application of 0.0017 Watt/ml/min density increased soluble content of primary and secondary sludges. In batch fermentations, sonicated secondary sludge improved fermentation over unsonicated secondary sludge. A maximum net VFA production of 130 mg VFA HAC /I was observed in the secondary sludge batch fermentation. In this research work, an investigation into inhibiting VFA degradation in secondary sludge batch fermentations was also carried out. The effects of a methanogenic bacteria inhibitor (bromoethane sulfonic acid) and low pH (range of 4.02-6.07) were considered. The addition of 1 mM bromoethane sulfonic acid (BES) in secondary sludge (1% TS) batch fermentation successfully inhibited VFA degradation. pH values as low as 4.02 showed an inhibitory effect on secondary sludge (1% TS) batch fermentation which led to poor hydrolysis and hence no net VFA generated during the test period. However, low pH values reduced the VFA degradation rate in the batch fermentations. Secondary sludge used in the present research showed the potential to generate VFA. The amount of VFA produced in the present work showed the potential to improve the performance of a BNR system. Moreover, in batch fermentations, VFA generation was improved using various pre-treatments like sonication and BES addition

Development and fabrication of a solar cell junction processing system

Development of a pulsed electron beam subsystem, wafer transport system, and ion implanter are discussed. A junction processing system integration and cost analysis are reviewed. Maintenance of the electron beam processor and the experimental test unit of the non-mass analyzed ion implanter is reviewed

Structure and Finances of U.S. Farms: 2005 Family Farm Report

Most farms in the United States- 98 percent in 2003- are family farms. They are organized as proprietorships, partnerships, or family corporations. Even the largest farms tend to be family farms, although they are more likely to have more than one operator. Very large family farms and nonfamily farms account for a small share of farms but a large-and growing-share of farm sales. Small family farms account for most of the farms in the United States but produce a modest share of farm output. Median income for farm households is 10 percent greater than the median for all U.S. households, and small-farm households receive substantial off-farm income. Many farm households have a large net worth, reflecting the land-intensive nature of farming.Agricultural Finance, Consumer/Household Economics, Industrial Organization,

Health Coverage and Access to Care for Hispanics in "New Growth Communities" and "Major Hispanic Centers"

Examines healthcare coverage for Hispanics when they migrate from cities to smaller urban and rural areas, and encounter roadblocks such as language barriers, lack of insurance, and access to health clinics

Growing Farm Size and the Distribution of Farm Payments

Crop production is shifting to much larger farms. Since government commodity payments reflect production volumes for program commodities, payments are also shifting to larger farms. In turn, the operators of very large farms have substantially higher household incomes than other farm households, and as a result government commodity payments are also shifting to much higher-income households. Since the changes in farm structure appear to be ongoing, commodity payments will likely, under current policies, continue to shift to higher income households. This brief uses 2003 Agricultural Resource Management Survey (ARMS) data to detail the shifts.Farm structure, commodity programs, farm payments, farm household income, farm income, farm program payments, ERS, USDA, Agricultural and Food Policy, Industrial Organization,

Million-Dollar Farms in the New Century

Million-dollar farms—those with annual sales of at least $1 million—accounted for about half of U.S. farm sales in 2002, up from a fourth in 1982 (with sales measured in constant 2002 dollars). By 2006, million-dollar farms, accounting for 2 percent of all U.S. farms, dominated U.S. production of high-value crops, milk, hogs, poultry, and beef. The shift to million-dollar farms is likely to continue because they tend to be more profitable than smaller farms, giving them a competitive advantage. Most million-dollar farms (84 percent) are family farms, that is, the farm operator and relatives of the operator own the business. The million-dollar farms organized as nonfamily corporations tend to have no more than 10 stockholders.Contracting, family farms, farm businesses, farm financial performance, farm-operator household income, farm operators, farm structure, farm type, million-dollar farms, Farm Management,

OFF-FARM LABOR AND THE STRUCTURE OF U.S. AGRICULTURE: THE CASE OF CORN/SOYBEAN FARMS

While the growing importance of off-farm earnings suggests large benefits accrue to farmers from efforts to expand off-farm income opportunities, survival still depends on greater efficiency. To comprehensively gauge the economic health of farm operator households we interpret off-farm income as an output along with corn, soybeans, livestock, and other crops. To accomplish this task we use two related methodologies. First, using 2000 data, we setup a multiactivity cost function to analyze labor allocation decisions within the farm operator household and also to estimate returns to scale and scope. Second, using 1996-2000 data, we follow an input distance function approach to estimate returns to scale, technical progress, cost economies, and technical efficiency--and compare the relative performance of farm operator households with and without off-farm wages and salaries. Our preliminary results suggest that over our sample period, scale economies are a primary factor driving up farm operator household size and decreasing the competitiveness of small farm operator households in the base farm operator household model where off-farm income is constrained to zero. But small farm operator households appear to achieve efficiency levels more comparable to larger farm operator households when off-farm income is accommodated. The evidence therefore suggests that while short-falls in these productivity components are decreasing the competitiveness of small farm operator households as agricultural structure changes, corn/soybean farm operator households have partially adapted to such pressures by increasing off-farm income and, therefore, achieving economies of scope.Labor and Human Capital,

ERS Farm Typology for a Diverse Agricultural Sector

The Economic Research Service (ERS) developed a farm typology which categorizes farms into more homogeneous groups than do classifications based on sales volume alone, producing a more effective policy development tool. The typology is used to describe U.S. farms.Farm Management,

Differences in Canadian and U.S. Farm Structure: What the Canadian Farm Typology Shows

Canadian and U.S. farms vary widely in size and other characteristics, ranging from very small retirement and residential farms to firms with sales in the millions. Agriculture and Agri-Food Canada (AAFC) and the United States Department of Agriculture’s (USDA’s) Economic Research Service (ERS) have each developed a farm typology to classify farms into more homogeneous groups. These typologies provide useful insights into farm structure in each country. It is difficult, however, to use the typologies to compare farm structure in Canada and the United States, because the definitions within the two typologies differ. To make direct comparisons of farm structure in the two countries the Canadian typology was applied to the farms in both nations.Crop Production/Industries, Farm Management,