Enhancing chemical phosphorus precipitation from tapioca starch anaerobic digestion effluent in a modified pilot-scale fluidized bed reactor.

This study aimed to evaluate the possibility of P precipitation as struvite from real anaerobic digestion (AD) effluent of tapioca starch processing. The results showed that at a pH of 9, and without Mg:P molar adjustment, P recovery was at 85%. The percentage of P recovery was increased to 90% and P contained in precipitates was at 11.80-14.70 wt% P, which is higher than commercial single superphosphate fertilizer (SSP, 18-22 wt% P2O5). This was achieved by controlling mixing at 200-400 rpm and upflow velocity at 50-200 cm min-1 inside a fluidized bed reactor (FBR). Based on SEM-EDX, powder XRD, phase identification by profile matching, and FT-IR analysis, the results demonstrated that recovered precipitates formed struvite predominantly. In addition, results of the woodchip ash additions and the one-way ANOVA based-RSM analysis revealed that mixing, the solution pH, and the woodchip ash intensely affected P recovery with the optimum condition found at 400 rpm, pH9, 4 g L-1, respectively. Ash addition enhanced P recovery efficiency but decreased the product's purity. Total costs of P recovery varied considerably from 0.28 to 7.82 USD∙(kg P)-1 depending on chemical consumption and %P content in recovered products. Moreover, the total cost was reduced by 57% from 7.82 USD∙(kg P)-1 (profit margin: -4.30 to -2.82) by a single mixing operation to 3.35 USD∙(kg P)-1 (profit margin: +0.17 to +1.65) employing coupling effect of mixing and Vup. The results indicate that P recovery from tapioca starch AD effluent not only provides a good-quality alternative slow-release P fertilizer, but also helps to curtail environmental problems due to excessive P and nitrogen discharge. These findings also demonstrate the ways of recovering nutrients from an abundant renewable resource that are relevant to simultaneous waste utilization during pollution controls.

Enhancing anaerobic co-digestion of primary settled-nightsoil sludge and food waste for phosphorus extraction and biogas production: effect of operating parameters and determining phosphorus transformation.

The study aimed to comprehensively determine P extraction efficiency and co-digestion of food waste (FW) and primary settled-nightsoil sludge (PSNS) process performance influenced by different hydraulic retention times (4, 7, 10, and 15 days) and mixture ratios of FW:PSNS in substrates (100:0, 75:25, 50:50, 25:75, and 0:100). P-transformation was evaluated to identify P fractionation in both supernatant and sludge accumulated in reactors. The results showed that anaerobic co-digestion was inhibited by the accumulation of undigested feedstock due to higher %PSNS found in AD4 (25FW:75PSNS) and AD5 (100PSNS). A more stable process was found in AD2 (75FW:25PSNS) under hydraulic retention time (HRT) 15 days in which COD removal efficiency and P release were 97.2 and 80.2%, respectively. This recommended condition allowed a high organic loading rate (OLR) at 12 gVS/L/day resulting in the highest biogas yield of 0.93 L/L/day. Distribution of P data demonstrated that most of P in feedstock was deposited and accumulated in sediment up to 97.8%. Poor biodegradability resulting from using shortened HRT led to high increased P-solid content in effluent. In addition, available P in effluents and accumulated P-solids in sediment obtained from the AcoD process has the potential to serve as sources for P recovery.

Considering the effects of ambient particulate matter on the lung function of motorcycle taxi drivers in Bangkok, Thailand.

The motorcycle taxi drivers of Bangkok have been heavily exposed to high concentrations of PM10 (particulate matter with an aerodynamic diameter ≤10 µm), and the impact of this on their lungs has been neither documented nor studied. This study examines the association between exposure to PM10 and lung function decline among motorcycle taxi drivers. A cross-sectional study was conducted in Bangkok between two groups: a subject group of motorcycle taxi drivers and control group of enclosed vehicle taxi drivers. The findings of the Thailand Pollution Control Department were used to estimate the annual ambient PM10 concentration levels in the metropolis. Pulmonary functions of motorcycle taxi drivers and enclosed vehicle taxi drivers were measured and compared using the Mann-Whitney test. Multiple linear regression analysis was applied to estimate the effects of PM10 exposure on the lung function of motorcycle taxi drivers. A total of 1283 motorcycle taxi drivers and 600 taxi drivers were investigated. The mean forced expiratory volume in 1 sec/forced vital capacity (FEV1/FVC) of the motorcycle taxi drivers was significantly lower than that of the taxi drivers (P < 0.001). The mean FEV1/FVC of motorcycle taxi drivers exposed to ≥50 µg/m3 PM10 was statistically lower (-2.82%; 95% confidence interval [CI]: -4.54% to -1.09%) and the mean % vital capacity (%VC) of those exposed to 40-49.9 µg/m3 PM10 was statistically lower than that of motorcycle taxi drivers exposed to <30 µg/m3 PM10 (-3.33%; 95% CI: -5.79% to -0.87%). Motorcycle taxi drivers were directly exposed to air pollution in their working environment. As a result, their lung function might decrease more than that of enclosed vehicle taxi drivers. With the possible exposure to ≥50 µg/m3 PM10, the vehicular emission standards should be vigorously enforced. Further investigation is warranted to clarify the effect of lung dysfunction on the work and lifestyle of motorcycle taxi drivers. IMPLICATIONS: Motorcycle taxi drivers are directly exposed to air pollution in their work environment; therefore, their lung function might decrease more than that of enclosed vehicle taxi drivers, especially when exposed to ≥50 µg/m3 PM10. World Health Organization (WHO) vehicular emission standards should be recognized and eventually enforced.