Optimization models for siting water quality monitoring stations in a catchment

A water quality monitoring network (WQMN) must be designed so as to adequately protect the water quality in a catchment. Although a simulated annealing (SA) method was previously applied to design a WQMN, the SA method cannot ensure the solution it obtained is the global optimum. Therefore, two new linear optimization models are proposed in this study to minimize the deviation of the cost values expected to identify the possible pollution sources based on uniform cost (UC) and coverage elimination uniform cost (CEUC) schemes. The UC model determines the expected cost values by considering each sub-catchment being covered by which station, while the CEUC model determines the coverage of each station by eliminating the area covered by any upstream station. The proposed models are applied to the Derchi reservoir catchment in Taiwan. Results show that the global optimal WQMN can be effectively determined by using the UC or CEUC model, for which both results are better than those from the SA method, especially when the number of stations becomes large.     

Evaluating the Management Effectiveness of Five Protected Areas in Taiwan Using WWF’s RAPPAM

This study adopts and modifies the WWF Rapid assessment and prioritization of protected areas management methodology (RAPPAM) to evaluate the management effectiveness of five protected areas in Taiwan. The results indicate that, unlike the situation in most developing countries, the threats and pressures faced by protected areas in Taiwan come mainly from the outside-with pollution as the most common pressure and threat, and difficult for their management authorities to deal with effectively. The categories and extent of these pressures and threats are related to remoteness and geographic location of the protected areas. All five cases under study reveal a similar management approach, clear management goals, adequate basic infrastructure and clear management decision-making; on the down side, however, all of them suffer from the lack of an effective comprehensive management plan, inadequate or poor quality human resources and insufficient funding. The present study suggests that first priority should be given to strengthening management planning in order to improve management effectiveness of protected areas in Taiwan. The adjustment made to RAPPAM in this study was to amend and take the format of the management plan as the basis for evaluation material preparations and open the discussion to encourage stakeholders' participation to open the dialogue among them. The results indicate that, although the system evaluation design still has some constraints, the quality of information collected is improved and can respond more directly to the specific demands of the respective areas.     

Potential assessment of establishing a renewable energy plant in a rural agricultural area

An evaluation of the green energy potential generated from biogas and solar power, using agricultural manure waste and a photovoltaic (PV) system, was conducted in a large geographical area of a rural county with low population density and low pollution. The studied area, Shoufeng Township in Hualien County, is located in eastern Taiwan, where a large amount of manure waste is generated from pig farms that are scattered throughout the county. The objective of the study is to assess the possibility of establishing an integrated manure waste treatment plant by using the generated biogas incorporated with the PV system to produce renewable energy and then feed it back to the incorporated farms. A filed investigation, geographic information system (GIS) application, empirical equations development, and RETScreen modeling were conducted in the study. The results indicate that Shoufeng Township has the highest priority in setting up an integrated treatment and renewable energy plant by using GIS mapping within a 10-km radius of the transportation range. Two scenarios were plotted in assessing the renewable energy plant and the estimated electricity generation, plus the greenhouse gas (GHG) reduction was evaluated. Under the current governmental green energy scheme and from a long-term perspective, the assessment shows great potential in establishing the plant, especially in reducing environmental pollution problems, waste treatment, and developing suitable renewable energy.     

Pollution and variation of stream nitrate in a protected high-mountain watershed of Central Taiwan: evidence from nitrate concentration and nitrogen and oxygen isotope compositions

This study analyzed the concentration and stable nitrogen (δ(15)N) and oxygen (δ(18)O) isotopic compositions of water NO (3) (-) , as well as NO (3) (-) concentration and δ(15)N values of soils and manure-sourced fertilizers to assess pollution and variation in stream nitrate at the watershed of the Chi-Chia-Wan Stream (CCWS), a protected high-mountain stream in Central Taiwan. Results indicate a gully (G1) that contributes significantly high NO (3) (-) concentration water (up to 122 mg/L) to trunk water as the major pollution source of CCWS. The high NO (3) (-) concentration gully water has a close relationship with manure-sourced fertilizer with both having compatible enriched δ(15)N values. Results also indicate that water mixing over isotopic fractionation processes such as denitrification or assimilation is the major process accounting for variations in concentrations and isotopic values for stream NO (3) (-) . Incorporation of gully/tributary water of high NO (3) (-) concentration increases both the concentration and isotopic values of trunk water and vice versa for the incorporation of low NO (3) (-) concentration tributary water. Despite G1 contributing high NO (3) (-) concentration water to the trunk water of CCWS, the concentration of the trunk water is only slightly elevated and is still lower than the required water quality standard due to much lower drainage of the gully water compared to trunk water's runoff. In addition to gully or tributary water and rainwater, NO (3) (-) derived from soil is another important contributor to trunk water. The NO (3) (-) contribution of soil to trunk water is greater in summer than in winter. Additionally, NO (3) (-) concentrations in soil from ex-cultivated land are significantly lower than that in cultivated land. This means that NO (3) (-) contribution from ex-cultivated land soil to trunk water is small and demonstrates that the land-recovery plan that has been underway in the studied watershed for sometime is effective.     

Control of petroleum-hydrocarbon contaminated groundwater by intrinsic and enhanced bioremediation

In the first phase of this study, the e ectiveness of intrinsic bioremediation on the containment of petroleum hydrocarbons was evaluated at a gasoline spill site. Evidences of the occurrence of intrinsic bioremediation within the BTEX (benzene, toluene, ethylbenzene, and xylenes) plume included (1) decreased BTEX concentrations; (2) depletion of dissolved oxygen (DO), nitrate, and sulfate; (3) production of dissolved ferrous iron, methane, and CO2; (4) deceased pH and redox potential; and (5) increased methanogens, total heterotrophs, and total anaerobes, especially within the highly contaminated areas. In the second phase of this study, enhanced aerobic bioremediation process was applied at site to enhance the BTEX decay rates. Air was injected into the subsurface near the mid-plume area to biostimulate the naturally occurring microorganisms for BTEX biodegradation. Field results showed that enhanced bioremediation process caused the change of BTEX removal mechanisms from anaerobic biodegradation inside the plume to aerobic biodegradation. This variation could be confirmed by the following field observations inside the plume due to the enhanced aerobic bioremediation process: (1) increased in DO, CO2, redox potential, nitrate, and sulfate, (2) decreased in dissolved ferrous iron, sulfide, and methane, (3) increased total heterotrophs and decreased total anaerobes. Field results also showed that the percentage of total BTEX removal increased from 92% to 99%, and the calculated total BTEX first-order natural attenuation rates increased from 0.0092% to 0.0188% per day, respectively, after the application of enhanced bioremediation system from the spill area to the downgradient area (located approximately 300 m from the source area).     

Health risk assessment of groundwater arsenic pollution in southern Taiwan

Residents of the Pingtung Plain, Taiwan, use groundwater for drinking. However, monitoring results showed that a considerable portion of groundwater has an As concentration higher than the safe drinking water regulation of 10 μg/L. Considering residents of the Pingtung Plain continue to use groundwater for drinking, this study attempted to evaluate the exposure and health risk from drinking groundwater. The health risk from drinking groundwater was evaluated based on the hazard quotient (HQ) and target risk (TR) established by the US Environmental Protection Agency. The results showed that the 95th percentile of HQ exceeded 1 and TR was above the safe value of threshold value of 10^?6. To illustrate significant variability of the drinking water consumption rate and body weight of each individual, health risk assessments were also performed using a spectrum of daily water intake rate and body weight to reasonably and conservatively assess the exposure and health risk for the specific subgroups of population of the Pingtung Plain. The assessment results showed that 0.01–7.50 % of the population’s HQ levels are higher than 1 and as much as 77.7–93.3 % of the population being in high cancer risk category and having a TR value >10^?6. The TR estimation results implied that groundwater use for drinking purpose places people at risk of As exposure. The government must make great efforts to provide safe drinking water for residents of the Pingtung Plain.     

The development of stream temperature model in a mountainous river of Taiwan

Formosan landlocked salmon is an endangered species and is very sensitive to stream temperature change. This study attempts to improve a former stream temperature model (STM) which was developed for the salmon’s habitat to simulate stream temperature more realistically. Two modules, solar radiation modification (SRM) and surface/subsurface runoff mixing (RM), were incorporated to overcome the limitation of STM designed only for clear-sky conditions. It was found that daily temperature difference is related to cloud cover and can be used to adjust the effects of cloud cover on incident solar radiation to the ground level. The modified model (STM + SRM) improved the simulation during a baseflow period in both winter and summer with the Nash-Sutcliffe efficiency coefficient improved from 0.37 (by STM only) to 0.71 for the winter and from ?0.18 to 0.70 for the summer. On the days with surface/subsurface runoff, the incorporation of the two new modules together (STM + SRM + RM) improved the Nash-Sutcliffe efficiency coefficient from 0.00 to 0.65 and from 0.29 to 0.83 in the winter and the summer, respectively. Meanwhile, the contributions of major thermal sources to stream temperature changes were identified. Groundwater is a major controlling factor for regulating seasonal changes of stream temperature while solar radiation is the primary factor controlling daily stream temperature variations. This study advanced our understanding on short-term stream temperature variation, which could be useful for the authorities to restore the salmon’s habitat.     

Control strategies for biohydrogen production by immobilized co-culture of Clostridium butyricum and Rhodopseudomonas palustris

In this study, we evaluated biohydrogen production of Clostridium butyricum and Rhodopseudomonas palustris by immobilized co-culture. Effects of free cells and immobilized cells, immobilized biomass ratio, sucrose concentration, and initial pH on hydrogen production were investigated. The immobilized co-culture can achieve high cumulative hydrogen volume yield (604 mL) as compared to free co-culture cumulative hydrogen volume (513 mL) while the initial sucrose concentration was 17.8 g/L. The optimum C. butyricum/R. palustris ratio was 1:10, yielding the highest cumulative hydrogen (728 mL). High sucrose concentration (above 35.6 g/L) would inhibit hydrogen production. The optimal initial pH value for hydrogen production of immobilized co-culture was 7.0 (cumulative hydrogen volume 830 mL).     

A model for the implementation of a two-shift municipal solid waste and recyclable material collection plan that offers greater convenience to residents

Separating recyclables from municipal solid waste (MSW) before collection reduces not only the quantity of MSW that needs to be treated but also the depletion of resources. However, the participation of residents is essential for a successful recycling program, and the level of participation usually depends on the degree of convenience associated with accessing recycling collection points. The residential accessing convenience (RAC) of a collection plan is determined by the proximity of its collection points to all residents and its temporal flexibility in response to resident requirements. The degree of proximity to all residents is determined by using a coverage radius that represents the maximum distance residents need to travel to access a recycling point. The temporal flexibility is assessed by the availability of proximal recycling points at times suitable to the lifestyles of all residents concerned. In Taiwan, the MSW collection is implemented at fixed locations and at fixed times. Residents must deposit their garbage directly into the collection vehicle. To facilitate the assignment of collection vehicles and to encourage residents to thoroughly separate their recyclables, in Taiwan MSW and recyclable materials are usually collected at the same time by different vehicles. A heuristic procedure including an integer programming (IP) model and ant colony optimization (ACO) is explored in this study to determine an efficient two-shift collection plan that takes into account RAC factors. The IP model has been developed to determine convenient collection points in each shift on the basis of proximity, and then the ACO algorithm is applied to determine the most effective routing plan of each shift. With the use of a case study involving a city in Taiwan, this study has demonstrated that collection plans generated using the above procedure are superior to current collection plans on the basis of proximity and total collection distance.