Enrichment of <Superscript>15</Superscript>N/<Superscript>14</Superscript>N in wastewater-derived effluent varies with operational performance of treatment systems: implications for isotope monitoring in receiving environments

Stable nitrogen isotope ratios are routinely used to trace the dispersion and assimilation of wastewater-derived N in receiving environments, but few isotope studies have investigated wastewater treatment plants and ponds themselves. An improved understanding of N isotope compositions in effluent will help assess treatment plant processes and performance and will help trace sources of excess nutrients in receiving environments. Here, we assess N budgets and treatment processes in seven wastewater treatment plants and wastewater stabilisation ponds in northern Australia based on concentrations and isotope ratios of N in effluent. We show that δ¹⁵N values in effluent are linked to treatment type, effectiveness of conversion of ammonia and levels of gaseous N emissions. These relationships suggest that N isotope monitoring of wastewater treatment plants and ponds can provide an integrated assessment of treatment performance and gaseous N emissions on a pond- or plant-wide scale that is not readily available through other methods. Our findings further imply that monitoring N isotope ratios in receiving environments cannot be assumed to be universally effective as their sensitivity to uptake of wastewater-derived N will vary with the characteristics of individual treatment systems. Paradoxically, N isotope monitoring is less effective where treatment systems are functioning poorly and where monitoring needs are the greatest.     

Assessment of the mechanical stability and chemical leachability of immobilized electroplating waste

The effectiveness of cement based treatment technology, in immobilizing chromium laden electroplating sludge was assessed by conducting toxicity characteristic leaching procedure (TCLP). The mechanical stability of the blocks was tested by measuring the compressive strength. Other leaching tests such as NEN 7341 test, ANS 16.1 and multiple TCLP (MTCLP) test conducted on select solidified blocks showed that chromium was immobilized by the binder studied. A linear relationship was obtained between the cumulative fraction of chromium leached (CFL) and square root of time in the solidified samples proving that diffusion is the controlling mechanism for leaching of chromium. The leachability indices (LI) obtained for the solidified materials using cement and cement-fly ash system (EPC6, EPFC6A and EPFC6B) satisfy the guidance value as per US NRC, which clearly indicates that chromium is well retained within the solid matrix. Chromium concentrations in the TCLP leachates of the above mix ratios were well within the regulatory level of United States Environmental Protection Agency (USEPA). Molecular characterization of the solidified material was carried out using Fourier transformation infra red (FTIR) technique.     

Putting houses in place:1 rebuilding communities in post‐tsunami Sri Lanka

This paper interrogates the social and political geographies of resettlement and reconstruction of temporary and permanent shelters, which are fundamental to rebuilding tsunami‐affected communities. War and ethnic cleavages are an endemic feature of Sri Lanka's social polity, and uneven development processes in the country are clearly visible. This paper draws attention to these spaces of inequality by drawing on in‐depth interviews and participant observation carried out in Eastern and Southern Sri Lanka. It argues that communities' concerns and anxieties regarding displacement and resettlement have tended to be articulated against prevailing fault lines of war and inequality. This is the backdrop against which communities negotiated the recovery process. My fieldwork shows that it is critical to understand that disaster and development relief are ingrained within context specificities. Relief efforts therefore need to recognise that the process of ‘putting houses in place’ should be embedded within local social relations.