Evolution of urban waste- and storm-water management in the region of Crete, Greece: a preliminary assessment.

The history of water supply and wastewater engineering in Crete Island (Greece) dates back more than ca 4,500 years, since the early Bronze Ages. In the Minoan era, it was recognized that the removal of wastewater and storm-water were necessary for communal living. The early Minoan developments in wastewater and storm-water collection and removal are the cornerstones on which modern cities are built. The evolution of wastewater and storm-water management from prehistoric to modern times in Crete is examined briefly in this paper. Information on the current status and future strategies for wastewater and storm-water management is also presented.

Fate of nitrogen for subsurface drip dispersal of effluent from small wastewater systems.

Subsurface drip irrigation systems apply effluent from onsite wastewater systems in a more uniform manner at a lower rate than has been possible with other effluent dispersal methods. The effluent is dispersed in a biologically active part of the soil profile for optimal treatment and where the water and nutrients can be utilized by landscape plants. Container tests were performed to determine the fate of water and nitrogen compounds applied to packed loamy sand, sandy loam, and silt loam soils. Nitrogen removal rates measured in the container tests ranged from 63 to 95% despite relatively low levels of available carbon. A Hydrus 2D vadose zone model with nitrification and denitrification rate coefficients calculated as a function of soil moisture content fit the container test results reasonably well. Model results were sensitive to the denitrification rate moisture content function. Two-phase transport parameters were needed to model the preferential flow conditions in the finer soils. Applying the model to generic soil types, the greatest nitrogen losses (30 to 70%) were predicted for medium to fine texture soils and soils with restrictive layers or capillary breaks. The slow transport with subsurface drip irrigation enhanced total nitrogen losses and plant nitrogen uptake opportunity.

Developing a holistic strategy for integrated waste management within municipal planning: challenges, policies, solutions and perspectives for Hellenic municipalities in the zero-waste, low-cost direction.

The present position paper addresses contemporary waste management options, weaknesses and opportunities faced by Hellenic local authorities. It focuses on state-of-the-art, tested as well as innovative, environmental management tools on a municipal scale and identifies a range of different collaboration schemes between local authorities and related service providers. Currently, a policy implementation gap is still experienced among Hellenic local authorities; it appears that administration at the local level is inadequate to manage and implement many of the general policies proposed; identify, collect, monitor and assess relevant data; and safeguard efficient and effective implementation of MSWM practices in the framework of integrated environmental management as well. This shortfall is partly due to the decentralisation of waste management issues to local authorities without a parallel substantial budgetary and capacity support, thus resulting in local activity remaining often disoriented and isolated from national strategies, therefore yielding significant planning and implementation problems and delays against pressing issues at hand as well as loss or poor use of available funds. This paper develops a systemic approach for MSWM at both the household and the non-household level, summarizes state-of-the-art available tools and compiles a set of guidelines for developing waste management master plans at the municipal level. It aims to provide a framework in the MSWM field for municipalities in Greece as well as other countries facing similar problems under often comparable socioeconomic settings.

Seasonal tertiary wastewater treatment in California: an analysis of public health benefits and costs.

A number of communities in the Central Valley of California have requested that seasonally based effluent limits be developed for their wastewater treatment facilities. These seasonal limits would be based on disinfected secondary treatment during the winter and disinfected tertiary treatment during the rest of the year. Such a request for seasonal limits raises a significant water quality policy question with regard to the costs and relative benefits of tertiary treatment during the winter season. A benefit-cost analysis for winter season tertiary wastewater treatment in California's Central Valley is presented here. The assumed societal benefit of winter tertiary treatment is enhanced water quality for recreational purposes, and thus reduced risk to public health. Based on the results of this analysis, between four and sixteen million recreation events would need to occur annually region-wide during the winter to justify the costs of winter tertiary treatment. A similar method and the information described herein could be used by the state water quality regulatory agency to develop a risk-based policy to consider seasonal limits.

Urban wastewater and stormwater technologies in ancient Greece.

The status of urban sewerage and stormwater drainage systems in ancient Greece is reviewed, based on the results of archaeological studies of the 20th century. Emphasis is given to the construction, operation, and management of sewerage and stormwater drainage systems during the Minoan period (2nd millennium B.C.). The achievements of this period in dealing with the hygienic and the functional requirements of palaces and cities, were so advanced that they can only be compared to modern urban water systems, developed in Europe and North America in the second half of the 19th century A.D. The advanced Minoan technologies were exported to all parts of Greece in later periods of the Greek civilization, i.e. in Mycenaean, Archaic, Classical, and Hellenistic periods.

Ultrafiltration of wastewater: effects of particles, mode of operation, and backwash effectiveness.

The effects that wastewater quality and mode of operation have on the performance of an asymmetric, hollow fiber, polysulfone, ultrafiltration (UF) membrane with a molecular weight cutoff of 100,000 Daltons were investigated. Performance was assessed through monitoring membrane flux, transmembrane pressure, effluent biochemical oxygen demand, and operational cost of the experimental system while treating filtered secondary, secondary, and filtered primary effluents. Fluxes achieved for filtered secondary (129-173 l/m2 h), secondary (101-158 l/m2 h), and filtered primary (20-41 l/m2 h) effluents were compared to those obtained at three other locations where similar UF systems were operated. A conceptual model of the impact of an insufficient backwash and of operating the UF system at constant flux on membrane performance is presented to explain the differences in fluxes. Employing pre-membrane granular filtration to remove a portion of the problematic particles in secondary effluent prior to UF led to optimal operational conditions. The costs associated with the operation of pre-membrane granular filtration were offset by the increase in production achieved. Although the use of recirculation could increase maintainable flux when treating a concentrated feed (e.g., filtered primary effluent), the associated costs were high. Improved UF performance was found to result from allowing flux to decline naturally, rather than using a constant flux mode of operation. The effluents produced when filtered secondary and secondary effluents were the feeds would be equivalent to an oxidized, coagulated, clarified, and filtered wastewater as per Title 22 California Wastewater Reclamation Criteria.

Time-dependent retardation model for chemical oxygen demand removal in a subsurface-flow constructed wetland for winery wastewater treatment.

The relative success of chemical oxygen demand (COD) removal models to describe measured rates of COD removal in a pilot-scale constructed wetland designed for treatment of high-strength winery wastewater are evaluated using retention times determined from tracer studies. Not surprisingly, two-parameter residual and retardation models better fit the measured removal data than single-parameter, first-order decay models for wastewater at average COD loadings up to nearly 5000 mg/L. The residual and retardation models yielded nearly equivalent fits to the measured data. However, the retardation model had more consistent parameters for COD removal data across different depth levels in the constructed wetland and at different loadings, and a slightly smaller sum of least-squared errors. The retardation model seems to be appropriate for constructed wetland design because it allows a steady decrease in COD with increased treatment time rather than a constant residual COD (C*) value. From the least-squares optimization procedure used to estimate model parameters (a volumetric rate constant, Kv, range of 3 to 12 d(-1)), nonrealistic, or physically meaningless, large C* values (C* range of 23 to 450 mg COD/L) that were dependent on COD loading were obtained, potentially underestimating the constructed wetland system's actual winery wastewater treatment potential. The optimal parameters for the retardation model applied to the pilot-scale constructed wetland ranged from 9 to 12 d(-1) for the initial degradation rate constant, Ko, and 2 to 5 d(-1) for the time-based retardation coefficient, b. These values should be verified for full-scale field systems based on field measurements currently underway.

Environmental engineering: energy value of replacing waste disposal with resource recovery

Although in the past, environmental engineering has been primarily concerned with waste disposal, the focus of the field is now shifting toward viewing wastes as potential resources. Because reclamation usually consumes less energy than producing new materials, increasing reclamation not only reduces pollution but saves energy. Technological innovations contributing to this shift are summarized here, and are variously classified as emerging technologies or research topics, as either new departures or incremental improvements, and as opportunistic innovations, or examples of a unifying strategy. Both liquid and solid waste examples are given, such as a recent discovery of effects in disinfecting microfiltered reclaimed wastewater with ultraviolet light. In addition to its value in reducing pollution and conserving energy, this reorientation of environmental engineering could contribute to a more general shift toward greater cooperation among organizations dealing with the environment.