Optimal Expansion Strategy Research Articles

Analisis Variabel Ekonomi Hijau (Green Economy Variable) Terhadap Pendapatan Indonesia (Tahun 2011-2020) dengan Metode SEM-PLS

The rapid economic development has the potential to cause negative impacts on the environment. Environmental problems that occur urge policies to implement green economy as the most urgent and effective environmental management tool. This research was conducted by analyzing the issue of implementing a green economy on Indonesia's economic growth. The country's growth by implementing a green economic system is a solution to achieving sustainable country development goals. This research is exploratory in nature using descriptive and inferential analysis techniques. The data used is in the 2011-2020 range (10 years) using the SEM-PLS data analysis technique. From this study it shows that there is a positive and significant influence between the green economy on state income with the result p (0.000) < 0.05 which gives a large effect of 0.965. The influence value of 0.965 means that the implementation of a green economy will make a significant contribution to increasing state revenues in Indonesia. Finally, from the empirical studies conducted, it was found that the country's development must involve a green system in the future with a focus on directions, policies, organizations, areas, capacities, and interventions from all parties as an optimal expansion strategy to achieve Indonesian economic activities that pay attention to environmental conditions.

Microvascular and Prognostic Effect in Lesions With Different Stent Expansion During Primary PCI for STEMI: Insights From Coronary Physiology and Intravascular Ultrasound.

BackgroundWhile coronary stent implantation in ST-elevation myocardial infarction (STEMI) can mechanically revascularize culprit epicardial vessels, it might also cause distal embolization. The relationship between geometrical and functional results of stent expansion during the primary percutaneous coronary intervention (pPCI) is unclear.ObjectiveWe sought to determine the optimal stent expansion strategy in pPCI using novel angiography-based approaches including angiography-derived quantitative flow ratio (QFR)/microcirculatory resistance (MR) and intravascular ultrasound (IVUS).MethodsPost-hoc analysis was performed in patients with acute STEMI and high thrombus burden from our prior multicenter, prospective cohort study (ChiCTR1800019923). Patients aged 18 years or older with STEMI were eligible. IVUS imaging, QFR, and MR were performed during pPCI, while stent expansion was quantified on IVUS images. The patients were divided into three subgroups depending on the degree of stent expansion as follows: overexpansion (>100%), optimal expansion (80%−100%), and underexpansion (<80%). The patients were followed up for 12 months after PCI. The primary endpoint included sudden cardiac death, myocardial infarction, stroke, unexpected hospitalization or unplanned revascularization, and all-cause death.ResultsA total of 87 patients were enrolled. The average stent expansion degree was 82% (in all patients), 117% (in overexpansion group), 88% (in optimal expansion), and 75% (in under-expansion). QFR, MR, and flow speed increased in all groups after stenting. The overall stent expansion did not affect the final QFR (p = 0.08) or MR (p = 0.09), but it reduced the final flow speed (−0.14 cm/s per 1%, p = 0.02). Under- and overexpansion did not affect final QFR (p = 0.17), MR (p = 0.16), and flow speed (p = 0.10). Multivariable Cox analysis showed that stent expansion was not the risk factor for MACE (hazard ratio, HR = 0.97, p = 0.13); however, stent expansion reduced the risk of MACE (HR = 0.95, p = 0.03) after excluding overexpansion patients. Overexpansion was an independent risk factor for no-reflow (HR = 1.27, p = 0.02) and MACE (HR = 1.45, p = 0.007). Subgroup analysis shows that mild underexpansion of 70%−80% was not a risk factor for MACE (HR = 1.11, p = 0.08) and no-reflow (HR = 1.4, p = 0.08); however, stent expansion <70% increased the risk of MACE (HR = 1.36, p = 0.04).ConclusionsStent expansion does not affect final QFR and MR, but it reduces flow speed in STEMI. Appropriate stent underexpansion of 70–80% does not seem to be associated with short-term prognosis, so it may be tolerable as noninferior compared with optimal expansion. Meanwhile, overexpansion and underexpansion of <70% should be avoided due to the independent risk of MACEs and no-reflow events.

Long-Term Expansion Planning of the Transmission Network in India under Multi-Dimensional Uncertainty

Considerable investment in India’s electricity system may be required in the coming decades in order to help accommodate the expected increase of renewables capacity as part of the country’s commitment to decarbonize its energy sector. In addition, electricity demand is geared to significantly increase due to the ongoing electrification of the transport sector, the growing population, and the improving economy. However, the multi-dimensional uncertainty surrounding these aspects gives rise to the prospect of stranded investments and underutilized network assets, rendering investment decision making challenging for network planners. In this work, a stochastic optimization model is applied to the transmission network in India to identify the optimal expansion strategy in the period from 2020 until 2060, considering conventional network reinforcements as well as energy storage investments. An advanced Nested Benders decomposition algorithm was used to overcome the complexity of the multistage stochastic optimization problem. The model additionally considers the uncertainty around the future investment cost of energy storage. The case study shows that deployment of energy storage is expected on a wide scale across India as it provides a range of benefits, including strategic investment flexibility and increased output from renewables, thereby reducing total expected system costs; this economic benefit of planning with energy storage under uncertainty is quantified as Option Value and is found to be in excess of GBP 12.9 bn. The key message of this work is that under potential high integration of wind and solar in India, there is significant economic benefit associated with the wide-scale deployment of storage in the system.

Optimized Expansion Strategy for a Hydrogen Pipe Network in the Port of Rotterdam with Compound Real Options Analysis

The port of Rotterdam is the largest seaport in Europe. To maintain its position, the harbor will have to anticipate global transitions such as transferring to sustainable energy. Hydrogen is seen as a promising energy carrier; however, future demand is uncertain. The current research investigates decision making under uncertainty and values flexibility. Compound real options analysis is applied to optimize the time-variant expansion strategies for a hydrogen pipe network. The trade-off between early investments and missed revenues when not investing in time determines the optimized expansion strategy. Moreover, the real options approach also provides the levelized unit price for hydrogen distribution, to cover the life cycle costs of the optimal expansion strategy. Finally, this real options approach offers flexibility to a decision maker as it allows for enhancing future decisions. The academic contribution of this research is a distinct perspective on a compound real options approach where the optimal strategic path is the key result of interest. This in contrast to other real options applications in the literature which focus on option value, exchange with limiting the options or do not visualize a strategic path. Moreover, this research demonstrates how stepwise expansion and decision making under uncertainty facilitate transitions such as the transition toward clean energy.

Regulatory T Cells for Acute Graft Versus Host Disease Prevention

BACKGROUND GVHD remains a major cause of morbidity and mortality after allo HSCT. The past few years have shown a number of successful advances in cellular therapies for the treatment of hematologic malignancies. It is logical to expand the use of these therapies earlier, in strategies aimed at prevention. Several studies showed that regulatory T cells (Treg) can reduce the incidence of aGVHD. METHODS Studies were identified using electronic databases (Medline, Embase, and Cochrane). Preclinical studies were excluded. Data analysis was performed using GraphPad Software 8.4.2. RESULTS 160 patients were identified from 7 clinical studies. 85% of the patients had acute leukemia and were in complete remission at the time of transplant. Tregs were isolated from either UCB or PB. Tregs were expanded ex-vivo using IL-2, CD3/CD28 ab coated beads and K562 cells in three studies (n=40). 1.Ex-vivo expanded Treg: In a phase I study (Brunstein et al) of UCB-derived Tregs in 23 pts undergoing double umbilical cord transplantation, Tregs were cultured with antiCD3/anti CD28 and IL-2. Ex-vivo expanded Tregs were given on day+1 and day+15. Eighteen pts received Treg cells at dose of &amp;gt;3x106 cells/kg. Grade II-IV aGvHD was seen in 39% of pts who received ≥3x106 cells/kg vs 43% in historical controls. In this study, CsA+MMF or sirolimus+MMF were used for GvHD prophylaxis. In a follow up study of 11 patients, Tregs were markedly expanded using K562 cells. Higher Treg doses were achieved up to 100x106cells/kg and the median proportion of CD4+CD127-FOXP3+ within the infused products was 87%. Grade II-IV aGVHD was 9% at 100 days vs 45% in control group. Treg cells were not detected in the peripheral blood after 14 days of infusion. In a phase II study (Kellner et al; Zeng et al), three of six pts undergoing PB MUD received ex-vivo expanded UCB-derived Tregs 1x106/kg at day-1. All developed aGVHD due to the high donor Tcon cells in the graft with donor Tcon:UCB Treg ratio as high as 356:1. Sixth patient was given 1x107 cells/kg Tregs in the presence of anti CD3/28 microbeads and IL-2 with Treg:Tcon ratio of 1:40. No aGVHD was observed in this patient compared to the others who received Treg at the dose of 1x106cells/kg. 2.Unexpanded Treg: In a study (Di Ianni et al) involving 26 high risk leukemia pts undergoing haplo-transplant with TBI based conditioning, 21 pts were infused with donor Tregs at a dose of 2x106 cells/kg and five pts were infused with Treg at a dose of 4x106 cells/kg on day -4, followed by Tcon infusion ranging from 0.5x106 to 2x106 cells/kg on day 0. No post-transplant immune suppression was given. Grade II-IV aGVHD was observed in 2 out of 26 patients who received 4x106cells/kg Tregs and 2x 106cells/kg Tcons. No GVHD was observed in pts who received 2x106cells/kg Tregs followed by 0.5-1x106 cells/kg Tcons. A phase II study by the same group (Martelli et al) reported on an additional 17 pts who received Tregs (2x106cells/kg) at day-4 co-infused with Tcon (1x106cells/kg) at day 0. Six of 41 (15%) evaluable pts developed grade II-IV aGVHD (vs 11% in historical cohort) with two pts requiring a short course of immunosuppression. Incidence of relapse was lower in Treg group than historical controls (5% vs 21%). In a phase I/II study (Meyer et al), 12 pts with hematological malignancies who underwent HLA-matched transplantation received purified Tregs (1-3x106cells/kg) on day0 followed by Tcon (1-3x106cells/kg) on day+2. GVHD was seen in 80% of pts with 50% being grade III in pts who received frozen Tregs. Upon revising protocol, 7 pts were given fresh Treg. The patients also received either tacrolimus or sirolimus for immunosuppression. None of 7 pts in revised cohort developed GVHD. Recent study applied hyper-fractionated TBI to the conditioning regimen in 12 pts out of 40 to further reduce leukemia relapse in Treg/Tcon based haplo-HSCT. Treg was administered at the dose of 2x106cells/kg and Tcon at 1x106cells/kg. No post-transplant GvHD prophylaxis was given. Grade II-IV aGVHD was observed in 12 pts. CONCLUSION These studies suggest that Treg therapy may represent an effective prevention strategy against acute GvHD (figure 1). Stimulated Treg expansion strategies and higher doses of Treg appear to be associated with lower incidence of aGVHD. Treg infusion was well-tolerated without serious adverse events. Large prospective clinical trials are warranted in order to establish the optimal infusion dose, optimal expansion strategies and dosing schedule. Disclosures No relevant conflicts of interest to declare.

A multi-period composite generation and transmission expansion planning model incorporating renewable energy sources and demand response

This study presents an evaluation of the potential impacts of Renewable Energy Sources (RES) and Demand Response (DR) on the Generation and Transmission Expansion Planning (GTEP) problem. This is highly essential in order to increase RES penetration in power systems thereby ensuring long term energy security and emissions reduction. GTEP with demand response is jointly considered so as to achieve an optimal expansion strategy for power systems by assisting the system planner make decisions about power system investments in order to meet the desired electricity demand. Therefore, the proposed model considers several levels of DR penetration in the planning system in order to assess its impact on the system performance. A multi-period multi-objective GTEP model was proposed and formulated as a Mixed Integer Quadratic Programming (MIQP) Problem. The developed MIQP was solved using the CPLEX 12.8.1 solver and is tested on two practical case studies: IEEE 24-bus and the real-world Nigerian Power system. Sensitivity analysis was performed on the system performance of the proposed model and the results indicate that an increase in penetration of DR resources in the planning procedure causes a decrease in the power generated, emissions and system costs whilst increasing RES utilization in power system.

Optimal expansion timing decisions in multi-stage PPP projects involving dedicated asset and government subsidies

The topic of investment timing in multi-stage public-private partnership (PPP) projects has not been received much attention so far. This study investigates optimal expansion timing decisions in multi-stage PPP projects under an uncertain demand and where the first-stage greenfield project involving a dedicated asset is immediately implemented as the PPP contract is closed, whereas the timing of the later expansion is flexibly decided according to the demand. In this setting, the optimal multiple stopping timing theory is adopted to model the expansion framework. Furthermore, we integrate a government subsidy, including an investment subsidy and revenue subsidy, into the expansion timing decisions. Through a hypothetical three-stage investment plan for a sanitary sewerage project, the optimal expansion strategies and the value of the multi-stage project before and after the subsidy are provided using a least squares Monte Carlo simulation. Also, the influences of a dedicated asset on the expansion strategies and project value are illustrated. In addition, we compare the incremental value before and after the subsidy and earlier expansion derived from two types of subsidies. The comparisons show that there is more incremental value for the revenue subsidy, and that the investment subsidy brings an earlier expansion.

"Game of Platforms: Strategic Expansion into Rival (Online) Territory"

Online platforms, such as Google, Facebook, and Amazon, are constantly expanding their activities while increasing the overlap in their service offerings. This paper asks: Is expansion into rival platforms’ services profit-maximizing when users’ platform choices endogenously change with expansion? We model an expansion game between two online platforms, both incumbents in distinct service markets, that provide their services free of charge to users and earn ad-based revenues. Platforms decide whether or not to expand by adding the service already offered by their rival. Expansion is costly and impacts users’ platform choice—namely, their choice of single- vs. multihoming, which, in turn, affects platform prices and profits derived from the advertisers’ side of the market. We demonstrate that, in equilibrium, platforms may choose not to expand. Strategic “no expansion” decisions are due to the quantity and price effects of changes in the user partition resulting from expansion. We further analyze the effects of expansion-driven changes in interplatform compatibility, expansion costs, probability of users’ ad engagement, switching costs, and intraplatform service complementarity and quality on the optimal expansion strategy. We then incorporate these considerations to derive an optimal expansion rule that can be used to guide managerial decision-making regarding expansion into a rival’s “territory.”

A coordinated production planning model with capacity expansion for supply chain networks

Developing a flexible supply chain is important for enterprises to face market volatility and diversity. In order to satisfy order requirements under demand uncertainty, this study constructs a coordinated production planning model of supply chain networks considering production capacity expansion. Besides, the proposed model involves batch production that is commonly used in many companies. The constructed model is then linearised as a mixed-integer linear programming problem to guarantee global optimality. The solution of the reformulated model determines the optimal production, transportation and inventory levels as well as the optimal batch production operations and capacity expansion strategy. Several numerical experiments are conducted to demonstrate the effectiveness of the proposed method and the impacts of production capacity expansion on the operations of the supply chain. [Received: 27 November 2017; Revised: 13 August 2018; Accepted: 29 December 2018].

Coordinated Planning Strategy for Electric Vehicle Charging Stations and Coupled Traffic-Electric Networks

The proliferation of electric vehicles (EVs) calls for an effective planning of charging stations by coupling the transportation network (TN) with the power distribution network (PDN). This paper conducts an interdisciplinary study on the coordinated planning strategy of EV charging stations in a coupled traffic-electric network. A comprehensive planning model is proposed, which determines the optimal expansion strategies for both TN and PDN, including sites and sizes of new charging stations, charging spots, TN lanes, and PDN lines. In TN, we use an unconstrained traffic assignment model (UTAM) to explicitly capture the steady-state distribution of traffic flows. In PDN, operating conditions are described by a linearized DistFlow. Moreover, EV charging demands and interdependency of TN and PDN are characterized by EV charging station location model. To retrieve a global optimal solution, an equivalent mixed-integer linear programming model with UTAM constraints is formulated for the coordinated planning model. Numerical experiments on coupled traffic-electric networks are conducted to validate the effectiveness of the proposed model and the solution method.

Relationship between Competitive Advantage and Success or Failure of Overseas Expansion in Small and Medium-Sized Manufacturers

The objective of this research is to clarify, empirically, how business factors influence the overseas expansion of small-to-medium-sized manufacturers (SMMs). With the internationalisation of a business, many SMMs have increased their overseas expansion in recent years. On the one hand, the probability of success for overseas expansion is not necessarily high. Of course, a lot of SMMs have succeeded in overseas expansion and expanded their revenue. On the other hand, however, there are many cases of SMMs failing in and withdrawing from the overseas expansion process. Although the influence of succeeding or failing is great in regard to corporate performance, there is a lack of clarification as to which business factors serve as the basis for SMMs’ decision-making. In this paper, research hypotheses are proposed to help measure the influential difference between the following select sources of competitive advantage: (a) external positioning and internal organizational capability; and (b) static perspective and dynamic perspective. Then, the select sources of competitive advantage are typified based on prior research. To verify the hypotheses, a questionnaire was implemented toward SMMs of Japan that expanded their business overseas. As a result, it became clear that the optimal overseas expansion strategies are different according to an SMM’s source of competitive advantage. As a contribution, it is expected that the results of this research will support the decision-making of SMMs toward overseas expansion.

Climate change impacts and adaptation strategies for a hydro-dominated power system via stochastic optimization

As outlined in the Paris Agreement on climate change, efforts to mitigate and adapt to climate change will require new modes of development of the energy sector including the transformation and expansion of power systems to low-carbon and more resilient designs. However, there is a need for more systematic tools to support decision-making processes in the context of climate change impacts and adaptation strategies for the energy and power sectors. For instance, quantitative approaches should be developed and implemented for the assessment of the impacts and hedging strategies associated with the uncertainties inherent to energy and power planning problems. This study addresses the development and implementation of an integrated model-based system analysis, which uses general circulation models, global sensitivity analysis, and stochastic optimization techniques, for the optimal design and planning of the Colombian power system in view of submitted climate pledges and climate change adaptation. It was found that during the 2015 to 2029 time frame, climate change will likely reduce the capacity factor of hydropower generation by 5.5–17.1%. Additionally, it was established that the independent effects of three key uncertain parameters, i.e., capacity factor of hydropower generation, gas prices, and emission reduction target, account for ∼96% of the variance in the total cost for the required expansion and operation of the power system. Furthermore, when uncertainty is taken into account, the optimal expansion strategy consists of rescheduling of investments in hydropower plants and investing more in carbon management technologies and renewable power plants to compensate for the uncertainty in hydropower generation, climate policy, and gas prices.

Optimal expansion planning of isolated microgrid with renewable energy resources and controllable loads

As the load demand in a microgrid increases, more distributed generators (DGs) should be installed to meet the demand, which makes the microgrid expansion planning very important. To obtain the optimal expansion strategy, a tri-level expansion planning framework is presented for an isolated microgrid in this study, which is composed of demand expansion, capacity optimisation and operation optimisation. The uncertainties of load forecasting are considered. Latin hypercube sampling method is utilised to generate the load demand scenarios. Controllable load is also considered in the expansion, which can be switched off and on as required. Considering the complexity of the operation optimisation problem, particle swarm optimisation is used to obtain the planning results. Finally, numerical simulations for an isolated microgrid in Weizhou Island, Guangxi, China are utilised to validate the effectiveness of the proposed model as well as its solving algorithm.

Evolution of a transmission network with high proportion of renewable energy in the future

Compared with other traditional energy sources, renewable energy, which results the less pollution and has numerous resources, is a significant factor in addressing the current issues of the serious environmental pollution and the resource depletion. Large-scale renewable energy integrated to the grid could bring change in both morphological structure and operation modes of energy transmission. Therefore, it is necessary to research the evolution mechanism of the future transmission network with a high proportion of the renewable energy. In this paper, an evolution framework of power system with high proportion of renewable energy is proposed. Firstly, a network equivalence and simplification based on power transfer distribution factors (PTDFs) is proposed, which can effectively simplify the decision-making process of evolution of large-scale power system. Then, an annual production simulation (8760 h) which takes into account renewable energy and load fluctuations is used to find out the bottleneck of the power grid. Based on the above methods, evolution strategy of power system with high proportion of renewable energy is studied for finding out optimal expansion strategy. A real power system of Zhejiang province is used as a test system. Test results demonstrate the feasibility of the proposed evolution framework.

A new evolutionary solution method for dynamic expansion planning of DG-integrated primary distribution networks

Reconstruction in the power system and appearing of new technologies for generation capacity of electrical energy has led to significant innovation in Distribution Network Expansion Planning (DNEP). Distributed Generation (DG) includes the application of small/medium generation units located in power distribution networks and/or near the load centers. Appropriate utilization of DG can affect the various technical and operational indices of the distribution network such as the feeder loading, energy losses and voltage profile. In addition, application of DG in proper size is an essential tool to achieve the DG maximum potential benefits. In this paper, a time-based (dynamic) model for DNEP is proposed to determine the optimal size, location and installation year of DG in distribution system. Also, in this model, the Optimal Power Flow (OPF) is exerted to determine the optimal generation of DGs for every potential solution in order to minimize the investment and operation costs following the load growth in a specified planning period. Besides, the reinforcement requirements of existing distribution feeders are considered, simultaneously. The proposed optimization problem is solved by the combination of evolutionary methods of a new Binary Enhanced Particle Swarm Optimization (BEPSO) and Modified Differential Evolution (MDE) to find the optimal expansion strategy and solve OPF, respectively. The proposed planning approach is applied to two typical primary distribution networks and compared with several other methods. These comparisons illustrate the effectiveness of the proposed DNEP approach.

Generating structured LPV-models with maximized validity region

A general approach for approximating the nonlinear dynamics of an aircraft model by a linear parameter varying (LPV) model of fixed structure (e.g. affine, polynomial, rational,…) is presented, which is a prerequisite for the application of several LPV based analysis and synthesis techniques. Starting from a given trim-point in the flight envelope, the approach tries to maximize the size of the region (flight envelope) around this trim point, for which the resulting LPV model describes the nonlinear model with sufficient accuracy. For this purpose the sensitivities of the model error with respect to an expansion of the flight envelope in the direction of specific parameters are used to get an optimal overall expansion strategy, which then yields a large validity region for the LPV model.

Optimal expansion of a drinking water infrastructure system with respect to carbon footprint, cost-effectiveness and water demand

Urban water infrastructure expansion requires careful long-term planning to reduce the risk from climate change during periods of both economic boom and recession. As part of the adaptation management strategies, capacity expansion in concert with other management alternatives responding to the population dynamics, ecological conservation, and water management policies should be systematically examined to balance the water supply and demand temporally and spatially with different scales. To mitigate the climate change impact, this practical implementation often requires a multiobjective decision analysis that introduces economic efficiencies and carbon-footprint matrices simultaneously. The optimal expansion strategies for a typical water infrastructure system in South Florida demonstrate the essence of the new philosophy. Within our case study, the multiobjective modeling framework uniquely features an integrated evaluation of transboundary surface and groundwater resources and quantitatively assesses the interdependencies among drinking water supply, wastewater reuse, and irrigation water permit transfer as the management options expand throughout varying dimensions. With the aid of a multistage planning methodology over the partitioned time horizon, such a systems analysis has resulted in a full-scale screening and sequencing of multiple competing objectives across a suite of management strategies. These strategies that prioritize 20 options provide a possible expansion schedule over the next 20 years that improve water infrastructure resilience and at low life-cycle costs. The proposed method is transformative to other applications of similar water infrastructure systems elsewhere in the world.

Effect of age and gender on cell proliferation and cell surface characterization of synovial fat pad derived mesenchymal stem cells

Cell based therapies are being investigated for biological repair of a variety of disorders. Previous work has shown that mesenchymal stem cells (MSCs) from older patients have reduced proliferation rates. As age is associated with greater musculoskeletal morbidity, e.g., osteoarthritis, an optimal MSC expansion strategy is required for older patients. In this in vitro study we investigate how age and gender affect MSC proliferation rate and cell surface characterization, as well as identify a relationship between seeding density and proliferation that could be applied to therapeutic MSC uses. Synovial fat pad derived MSCs were isolated and expanded from 14 patients undergoing total knee replacements. The cells were seeded at densities between 50 and 10,000 cells/cm(2) and cell proliferation studies, flow cytometry, and cell surface staining were performed. Females were found to have consistently higher cell proliferation and cell surface marker expression. The cell surface marker CD105 had a constant expression irrespective of age. A statistically significant inverse relationship was found between seeding densities and cell proliferation rates. This study has shown that patient characteristics do effect cell proliferation rate and cell surface characterization, but as seeding density has a significant relationship with proliferation rate, it can be altered, possibly along with other cell culturing strategies, to compensate for the effects of patient factors on MSCs. We have also shown that gender affects cell proliferation and cell surface characterization, something most previous studies may have failed to identify as they group male and female patients together.

Optimal expansion of a coastal wastewater treatment and ocean outfall system under uncertainty (I): simulation analysis

An ocean outfall system is an integrated engineering system in which a coastal wastewater treatment plant (WWTP) is connected with a pipeline that discharges wastewater effluent into a body of water. Safety factors to accommodate for uncertainty in modelling of such systems often result in a degree of wastewater treatment that is not cost-effective. This paper presents the first part of an integrated simulation and optimisation analysis to resolve some such uncertainties in the Cornell mixing zone expert system (CORMIX) model by testing it against a laboratory flume. CORMIX is a United States Environmental Protection Agency (USEPA)-supported mixing zone model for environmental impact assessment of regulatory mixing zones resulting from continuous point source discharges. This model especially emphasises prediction of plume geometry, flow classification, and dilution characteristics within an initial mixing zone of a receiving water body so that compliance with regulatory constraints can be evaluated. With the aid of a flume test, such information may be used as stochastic inputs to an optimisation model to assess the cost-effectiveness of discharge treatment. A total of 19 dye-study scenarios were designed and carried out for single-port (co-flow or counter-flow) and multi-port experiments according to the physical features of the outfall pipe to be expanded in the coastal environment of Taiwan Strait. The flume test showed a good agreement between CORMIX1/CORMIX2 models and the dye-study data. This approach is a stepwise, flexible technique allowing for continuous feedback of the varying design and operating conditions and the observed impacts on coastal waters and may be used to identify the optimal expansion strategy of an integrated coastal WWTP and ocean outfall system such as the case study presented for Kaohsiung, South Taiwan.

Optimal expansion of a coastal wastewater treatment and ocean outfall system under uncertainty (II): optimisation analysis

This paper presents an integrated simulation–optimisation assessment of the various physical, chemical, and microbiological processes that determine the transport and fate of key constitutes associated with coastal wastewater treatment and disposal effluents in coastal environments. The well-calibrated and validated ocean mixing simulation model – Cornell mixing zone expert system (CORMIX) – was employed in the first stage as an indispensable tool to simulate the initial dilution factor with respect to two major water quality indicators, biochemical oxygen demand (BOD) and Escherichia coli. The CORMIX outputs, which were obtained in a companion study, were used as the inputs in both deterministic and chance-constraint based stochastic programming models to evaluate a few alternatives for system planning and design. Such integration allowed the identification of the optimal expansion strategies for a large-scale coastal wastewater treatment and ocean outfall system in the city of Kaohsiung, South Taiwan. Research findings clearly indicate that the original alternative proposed by the city government, which had planned on upgrading the wastewater treatment process directly from the primary to the secondary level, is economically undesirable. Given the technology options of primary or enhanced primary treatment, in the most cost-effective expansion strategy, the optimal length of a newly constructed second ocean outfall pipe is no less than 1260 m in order to gain sufficient assimilative capacity in the ocean environment. With this strategy, the BOD standards in the ocean environment are met for both Classes B and A types of ocean waters. The reliability of this system design may be assessed by taking the stochastic characteristics of sewerage inflow and diffusion and dispersion processes into consideration. Such an optimisation analysis could eventually lead to considerable cost savings of up to 75% when compared to the original, officially favoured alternative.