Municipal Collection System Research Articles

Gram-negative bacteria carrying β-lactamase encoding genes in hospital and urban wastewater in Brazil.

Multidrug resistance mediated by β-lactamase in Gram-negative bacilli is a serious public health problem. Sewers are considered reservoirs of multiresistant bacteria due to presence of antibiotics that select them and favor their dissemination. The present study evaluated the antibiotic resistance profile and β-lactamases production in Gram-negative bacilli isolates from hospital sewage and urban wastewater treatment plants (UWWTP) in Brazil. Bacteria were isolated and identified with biochemical tests. Antibiotic susceptibility testing was performed by the disk-diffusion method and detection of extended-spectrum β-lactamase and carbapenemases by enzymatic inhibitor and conventional PCR. Differences in resistance to amoxicillin clavulanic, aztreonam, cefepime, and cefotaxime were observed in hospital sewage compared with urban sewage (p < 0.05). The multidrug-resistant phenotype was observed in 33.3% of hospital sewage isolates (p = 0.0025). β-lactamases genes were found in 35.6% of isolates, with the most frequent being blaKPC and blaTEM (17.8%), and blaSHV and blaCTX-M (13.3% and 8.9%, respectively). The data obtained are relevant, since the bacteria detected are on the priority pathogens list from the World Health Organization and hospital sewage could be released untreated into the municipal collection system, which may favor the spread of resistance. Changes in hospital sewage discharge practices, as well as additional technologies regarding effluent disinfection in the UWWTP, can prevent the spread of these bacteria into the environment and negative impact on water resources.

A Statewide Assessment of Infiltration and Inflow in Municipal Collection Systems in Maryland

A Statewide Assessment of Infiltration and Inflow in Municipal Collection Systems in Maryland

Truck sizing models for recyclables pick-up

Growing public concerns about the environmental consequences of waste disposal have led to an increase in recycling efforts. In many communities, curbside collection programs have been instituted for collecting recyclables from households for transfer to material recovery facilities. In most programs the cost of collection is the dominant cost. Despite the high cost and environmental importance of collecting recyclables from households, most municipal collection systems are designed and operated without a clear understanding of what factors drive those costs and how they might be reduced. In this paper, models for determining truck configurations, as well as optimal compartment sizes for recyclables collection are developed. Constraints arising from the operation of the trucks are formulated, and solution schemes are presented. In addition, a procedure for optimally partitioning a vehicle used to collect source-separated material is discussed. Several scenario based planning approaches are developed. Use of the truck sizing models as an industry decision tool and the associated benefits of applying the truck sizing models and the solution methodology to a contract based collection program are also discussed.

Modelling commercial/industrial waste generation: a Vienna, Austria case study

A study was done to determine in greater detail the volume of recyclable materials, sector-specific wastes and residual wastes from businesses within the Vienna city limits. To do so, a matrix-type model was applied to classify businesses according to commercial/industrial sector and business size. For small and medium-sized businesses, random samples were taken directly to determine average amounts and types of wastes generated; these figures were then extrapolated based on the number of employees. For large businesses, data taken from obligatory Waste Management Concepts were evaluated and augmented with an extrapolation. Because waste disposal channels were examined along with the volumes of wastes generated, it is possible to determine the impacts on the municipal collection system. The results are compared with data from the literature and other studies.

Modelling commercial/industrial waste generation: a Vienna, Austria case study

A study was done to determine in greater detail the volume of recyclable materials, sector-specific wastes and residual wastes from businesses within the Vienna city limits. To do so, a matrix-type model was applied to classify businesses according to commercial/industrial sector and business size. For small and medium-sized businesses, random samples were taken directly to determine average amounts and types of wastes generated; these figures were then extrapolated based on the number of employees. For large businesses, data taken from obligatory Waste Management Concepts were evaluated and augmented with an extrapolation. Because waste disposal channels were examined along with the volumes of wastes generated, it is possible to determine the impacts on the municipal collection system. The results are compared with data from the literature and other studies.