Ammonia volatilization from marsh-pond-marsh constructed wetlands treating swine wastewater

Ammonia (NH3) volatilization is an undesirable mechanism for the removal of nitrogen (N) from wastewater treatment wetlands. To minimize the potential for NH3 volatilization, it is important to determine how wetland design affects NH3 volatilization. The objective of this research was to determine how the presence of a pond section affects NH3 volatilization from constructed wetlands treating wastewater from a confined swine operation. Wastewater was added at different N loads to six constructed wetlands of the marsh-pond-marsh design that were located in Greensboro, North Carolina, USA. A large enclosure was used to measure NH3 volatilization from the marsh and pond sections of each wetland in July and August of 2001. Ammonia volatilized from marsh and pond sections at rates ranging from 5 to 102 mg NH3-N m(-2) h(-1). Pond sections exhibited a significantly greater increase in the rate of NH3 volatilization (p < 0.0001) than did either marsh section as N load increased. At N loads greater than 15 kg ha(-1) d(-1), NH3 volatilization accounted for 23 to 36% of the N load. Furthermore, NH3 volatilization was the dominant (54-79%) N removal mechanism at N loads greater than 15 kg ha(-1) d(-1). Without the pond sections, NH3 volatilization would have been a minor contributor (less than 12%) to the N balance of these wetlands. To minimize NH3 volatilization, continuous marsh systems should be preferred over marsh-pond-marsh systems for the treatment of wastewater from confined animal operations.     

Retention of nitrogen and phosphorous from liquid swine and poultry manures using highly characterized peats

This paper reports on research designed to test the hypothesis that differences in peat composition will cause differences in amounts of N and P retained during contact with liquid swine manure (LSM) and liquid poultry manure (LPM). Peat types representing a wide range of properties were tested in order to establish which chemical and physical properties might be most indicative of their capacities to retain N and P from LSM and LPM. Eight-percent slurries (peat/LSM and peat/LPM) were measured for total nitrogen (TKN) and total phosphorous (TP) after 6, 24 and 96 hours. Tests were done to determine the TKN and TP contents of these peats, the LSM, and the LPM, both before and after they were mixed together. The N and P retention results revealed that most peats worked reasonably well at retaining N and P from either LSM or LPM. However, some peats were more effective than others. These peats also decreased the N and P levels in the liquid portion of the LSM. Peats with higher N retention capacities tended to have lower ash contents, but higher macroporosities and total cellulose contents. Peats with higher P retention capacities tended to have lower bulk densities, ash contents, total guaiacyl lignins contents, fulvic acids contents, but higher microporosities, macroporosities, H contents, and total cellulose contents. Peats with higher N and P retention capacities also had humic acid contents between 5-7%. The results of this study suggest that if these peats are used to reduce odors and N and P contamination, possible byproducts could be the production of odorless fertilizers.     

Fate of polydimethylsilicone in biosolids-amended field plots

This research examined the fate of polydimethylsilicones (PDMS) in agricultural test plots amended with municipal biosolids. This 4 yr field study involved addition of 0, 15, and 100 Mg ha(-1) of municipal biosolids, which contained ambient concentrations of PDMS (1272 mg kg(-1) biosolids), to corn and soybean test plots. Soil samples collected at intermittent time intervals were analyzed for soil water, soil organic C, extractable PDMS and PDMS hydrolysis products. Above normal precipitation during the field study maintained soil water levels in excess of 100 g kg(-1) for most of the testing period of 1994-1998. Under these conditions half-lives for PDMS (based on field dissipation data) ranged from 876 to 1443 d. When biosolids amended soil samples were brought into the laboratory and subjected to more rapid drying, >80% of the PDMS was transformed to lower molecular weight hydrolysis products within 20 d. No difference in relative PDMS transformation rates were evident for soils that received PDMS in the form of a biosolids amendment or directly dosed to the soil (in the absence of biosolids) indicating little if any effect of direct PDMS-biosolids interactions on PDMS transformation rates. These results support that the overriding factor controlling the fate of PDMS in field soils is the soil moisture content.     

Simulated interior floods and the flood experience in urban communities

The Hydrologic Engineering Center (HEC-1) model was used to construct synthetic hydrographs for isolated interior urban floods. Flood peak and lag time were very well preserved in simulated flows. Total volume was not adequately expressed. Lag time varied inversely with both urban development and storm intensity. Peak discharge varied with storm intensity, but this variability was well defined only at very high urbanization levels. An 175% increase in storm intensity produced a change of about 15% in peak discharge. Claims for flood damage correlated well with estimates of peak flow and lag time combined. Other measures of flood experience also correlated with the two features. Within the range of storms utilized, urban development factors consistently outranked storm intensity as a determining factor in flood damage.     

Overview of regulatory/policy/economic issues related to carbon dioxide

This is an overview of Session 2c dealing with the regulatory, policy and economic issues related to carbon dioxide and its impact on global climate change. The information is taken from the two papers presented in this session (the U.S. Perspective by Dennis Leaf and the European Perspective by Hans J.H. Verolme) and from the panel discussion that took place at the end of the session. The overview focuses primarily on the policy responses of both the United States (US) and the United Kingdom (UK) to changes in global atmospheric pollution. To a lesser extent, the progress of policy responses to these changes is discussed. The United Nations Framework Convention on Climate Change (UNFCCC) has been signed and ratified by over 180 countries. The UNFCCC contained no binding targets or timetables for emissions reductions. The Kyoto Protocol [United Nations. Kyoto Protocol to the United Nations Framework Convention on Climate Change. UNEP.IUC/99/10. Chatlelaine, Switzerland: United Nations Environment Programme's Information Unit for Conventions, for the Climate Change Secretariat, 1997] to the UNFCCC did contain targets and timetables for reductions of greenhouse gases on the part of developed countries. The US has signed but not ratified the Kyoto Protocol. The US has experienced some movement to reduce greenhouse gas emissions on the part of various levels of government, as well as the private sector. The UK's commitment to reducing green house gases is laid down in the UK Climate Change Programme 2000. The UK is a member of the European Union (EU). In this context, an example of EU-wide progress, the voluntary agreement with car manufacturers to reduce CO(2) emissions in new vehicles, will be discussed. In addition, there will be some discussion on the UK CO(2) trading scheme that created the first market in the world in April 2001. Overall, the policy process is constantly informed by scientific research. In the case of climate change, much of this work is carried out under the auspices of international scientific panels.     

Planning STI/HIV prevention among refugees and mobile populations: situation assessment of Sudanese refugees

This article reflects an investigation of knowledge, attitudes and behaviours and HIV/STI prevalence of Sudanese refugees and Ethiopian sex workers in 1992. It represents one of the earliest such investigations within an African refugee population. The investigation took place in the Dimma refugee settlement in south-western Ethiopia and study participants included Sudanese refugee men and women and Ethiopian female sex workers. Methods used for this investigation included focus group discussions, behavioural surveys and serologic testing. The main outcome measures of the investigation were HIV/STI knowledge, attitudes and behaviours and biological markers for HIV, syphilis and herpes simplex 2. The study findings indicate that in the early 1990s, knowledge about AIDS and condom use was low among Sudanese refugee women and not one reported having ever used a condom. Furthermore, sexual contact between refugee men and sex workers was frequent during the time of this study and the prevalence of HIV and other STIs was high. The results confirm a widely held assumption that highly mobile and transient populations in Africa are susceptible to STIs and HIV, in large part due to their knowledge, attitudes and behaviours.