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Storm Water Issues In Biomass-fired Combined Heat And Power Plants Magnus Larsson, Jinying Yan* Kerstin Forsberg, Longcheng Liu Chemical Engineering, Royal Institute Of Te

Congress: 2015
Author(s): Jinying Yan (Stockholm, Sweden), Magnus Larsson, Kerstin Forsberg, Longcheng Liu
Royal Institute of Technology1

Keyword(s): Sub-theme 13: Non-conventional sources of water,
AbstractIntroduction

Two of the greatest environmental challenges facing today's society are those of sustainable energy production and water resource management. The International Energy Agency (IEA) estimates that global water consumption could be increasing with 2.5% per year through 2035 with energy-related consumption doubling over the same period. Based on this, one could argue that the water-energy nexus will be playing an increasingly important role when pursuing sustainable development in the future.

Stormwater is commonly given priority as an important water resource asset to which adequate investments are allocated. However, even though usually extensively accounted for on multiple levels in urban planning, corresponding management procedures for contaminated stormwater is usually not prescribed by the operational standards on many industrial sites. In Sweden, biomass-fired combined heat and power (bio-CHP) plants have the potential of contamination of stormwater run-off when the stormwater contact the biomass fuels (especially the recycled wood fuels).

In order to adequately manage this source of contaminants, a proper understanding of the parameters governing stormwater formation and composition, together with proper modeling tools, are needed. In this context, the EU Water Framework Directive has a strong impact on the storm water management procedures chosen and also includes requirements for water usage, utilisation efficiency and waste water discharge from local water district authorities. In the presented work, the main issues of stormwater in bio-CHP plants have been studied in terms of quality, magnitude and dynamics of discharge. The impacts of biomass fuel composition have also been investigated under the on-site storage conditions of biomass fuels. Generally these issues are not well-understood and not fully addressed so far.

Methodology:

The general methodology used for the characterisation of storm water run-off in a bio-CHP plant is illustrated in Figure 1. The evaluation is performed by using modelling combined with experimental investigation on site as indicated in the figure.

Results and Discussion:

The amount and quality of the run-off water leaving the storage site has been estimated by taking into account parameters such as local and seasonal conditions, sorption properties of biomass fuels affecting the run-off water quantity, as well as run-off water contamination and contaminate sources.

Mathematical models have been used to calculate run-off water volume. A number of relationships have been identified for the models. The relationships cover the impacts from precipitation, biomass fuel sorption properties and storage volume in the plant and the effect of local evaporation. Figure 2 shows an example of such a mathematical relationship.

The contamination of run-off water from the bio-CHP plant was showed mainly depending on how the precipitation water contacts with the biomass fuel (assuming outdoor storage), the fuel quality and leaching conditions. Figure 3 shows the leaching ability of recycled wood fuel under given fuel storage conditions, which could be used for estimation of the run-off quality.

Conclusions:

A general methodology has been developed for the characterisation of stormwater quality, magnitude and dynamics of run-off water discharge aspects in bio-CHP plants.

The run-off water volume from a bio-CHP plant has been identified to be a function of precipitation intensity, biomass fuel storage volume, water retention capacity of the biomass fuels, water evaporation from the plant area and run-off routing. For a bio-CHP plant, the final run-off water volume can be a small fraction of total precipitation in normal weather conditions.

The quality of run-off water from bio-CHP plants has been showed to mainly depend on precipitation intensity, the composition of biomass fuels, and its leaching ability together with surface characteristics of the biomass fuels in contact with the storm water. It is estimated that the total release potential from the recycled wood fuel could be much less than 1% for most of heavy metals. Other external factors such as run-off water from the areas other than the biomass fuel storage yard (dilution), evaporation (concentration), and external sources of contamination may also affect the quality of the run-off water finally leaving the plant.

Management of stormwater for a bio-CHP plant should be highly dependent on plant conditions and local authority requirements. This study provides a basis for the optimisation of stormwater management as the measures to utilise the non-conventional water source integrated with necessary recycle and cost-effective treatment for whole bio-CHP plant. Introduction Two of the greatest environmental challenges facing today's society are those of sustainable energy production and water resource management. The International Energy Agency (IEA) estimates that global water consumption could be increasing with 2.5% per year through 2035 with energy-related consumption doubling over the same period. Based on this, one could argue that the water-energy nexus will be playing an increasingly important role when pursuing sustainable development in the future. Stormwater is commonly given priority as an important water resource asset to which adequate investments are allocated. However, even though usually extensively accounted for on multiple levels in urban planning, corresponding management procedures for contaminated stormwater is usually not prescribed by the operational standards on many industrial sites. In Sweden, biomass-fired combined heat and power (bio-CHP) plants have the potential of contamination of stormwater run-off when the stormwater contact the biomass fuels (especially the recycled wood fuels). In order to adequately manage this source of contaminants, a proper understanding of the parameters governing stormwater formation and composition, together with proper modeling tools, are needed. In this context, the EU Water Framework Directive has a strong impact on the storm water management procedures chosen and also includes requirements for water usage, utilisation efficiency and waste water discharge from local water district authorities. In the presented work, the main issues of stormwater in bio-CHP plants have been studied in terms of quality, magnitude and dynamics of discharge. The impacts of biomass fuel composition have also been investigated under the on-site storage conditions of biomass fuels. Generally these issues are not well-understood and not fully addressed so far. Methodology The general methodology used for the characterisation of storm water run-off in a bio-CHP plant is illustrated in Figure 1. The evaluation is performed by using modelling combined with experimental investigation on site as indicated in the figure. Results and Discussion The amount and quality of the run-off water leaving the storage site has been estimated by taking into account parameters such as local and seasonal conditions, sorption properties of biomass fuels affecting the run-off water quantity, as well as run-off water contamination and contaminate sources. Mathematical models have been used to calculate run-off water volume. A number of relationships have been identified for the models. The relationships cover the impacts from precipitation, biomass fuel sorption properties and storage volume in the plant and the effect of local evaporation. Figure 2 shows an example of such a mathematical relationship. The contamination of run-off water from the bio-CHP plant was showed mainly depending on how the precipitation water contacts with the biomass fuel (assuming outdoor storage), the fuel quality and leaching conditions. Figure 3 shows the leaching ability of recycled wood fuel under given fuel storage conditions, which could be used for estimation of the run-off quality. Conclusions A general methodology has been developed for the characterisation of stormwater quality, magnitude and dynamics of run-off water discharge aspects in bio-CHP plants. The run-off water volume from a bio-CHP plant has been identified to be a function of precipitation intensity, biomass fuel storage volume, water retention capacity of the biomass fuels, water evaporation from the plant area and run-off routing. For a bio-CHP plant, the final run-off water volume can be a small fraction of total precipitation in normal weather conditions. The quality of run-off water from bio-CHP plants has been showed to mainly depend on precipitation intensity, the composition of biomass fuels, and its leaching ability together with surface characteristics of the biomass fuels in contact with the storm water. It is estimated that the total release potential from the recycled wood fuel could be much less than 1% for most of heavy metals. Other external factors such as run-off water from the areas other than the biomass fuel storage yard (dilution), evaporation (concentration), and external sources of contamination may also affect the quality of the run-off water finally leaving the plant. Management of stormwater for a bio-CHP plant should be highly dependent on plant conditions and local authority requirements. This study provides a basis for the optimisation of stormwater management as the measures to utilise the non-conventional water source integrated with necessary recycle and cost-effective treatment for whole bio-CHP plant.

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