The majority of the Southeast Asian region is composed of developing countries with urban, peri-urban, and rural areas whose anticipated change in wastewater treatment demand necessitates improvement in wastewater management. The narrative relating to the present scenario has been constructed via a rapid review structure using various literature concerning the state of wastewater management in the Southeast Asian region. Existing wastewater technology systems in the region have been studied in order to identify challenges in improving wastewater management. Several barriers across technology systems have been identified which shows that offering either centralised, decentralised, or cluster technology systems as one solution is not enough to address changing future demands for wastewater treatment. Thus, flexibility has been identified through the discussion as a key concept for proposing technology systems in regions where future demands require solutions in the present. We propose that investments in wastewater management in the developing countries of Southeast Asia require a perspective that focuses not only on what is appropriate for the present demand but also for the future.
The photolysis of chlorine by ultraviolet radiation (UV/chlorine) produces HO˙ and Cl˙, part of which further transforms into reactive chlorine species (RCS) like Cl2˙− and ClO˙. These radicals are responsible for the advanced oxidation effect of UV/chlorine processes. Recently, UV/chlorine processes gather much attention from researchers and practitioners and published papers on UV/chlorine processes have drastically increased, which were thoroughly reviewed in this paper for understanding the state of the art of these technologies. Fundamental studies elucidate that acidic conditions are favorable to UV/chlorine processes through a change in quantum yield of chlorine photolysis, equilibrium shifts of radical species, and a change in radical scavenger effect of free chlorine. Comparative studies reveal that UV/chlorine processes are usually more energy-efficient than UV/hydrogen peroxide and UV/persulfate processes. Although unfavorable byproducts formation by RCS reactions is apprehended, application researches in real waters show that UV/chlorine processes do not enhance disinfection byproducts formation very much. Since UV irradiation and chlorination are widely used unit operations, a barrier to install an UV/chlorine process into a conventional process is not high. It is desired to develop and optimize a whole process combined with other unit processes for maximizing benefits in water treatment in the future.
Brewers’ spent grain (BSG) and spent yeast cell (SYC) are the wastes from mashing and fermentation process of beer. The compositions of BSG were 24.49 ± 0.91% hemicellulose, 20.86 ± 0.60% cellulose and 9.62 ± 0.40% lignin, while those of SYC were 46.97 ± 0.07% protein, 21.32 ± 0.08% carbohydrate and 5.73 ± 0.57% lipids. BSG and SYC were acid hydrolyzed using different solid loadings at 5–24%. The optimal solid loadings for BSG and SYC that gave maximum sugar concentration were 15% and 24%, respectively. Sugar compositions in BSG hydrolysate were 22.02 ± 0.8% glucose, 45.83 ± 1.53% xylose, and 32.13 ± 2.3% arabinose, while those found in SYC hydrolysate were 31.43 ± 0.38% glucose and 69.57 ± 1.04% mannose. Both hydrolysates were used as nutrient sources at the same sugar concentration of 40 g/L for cultivation of three oleaginous yeasts, Trichosporonoides spathulata JU4-57, Rhodotorula mucilaginosa G43 and Yarrowia lipolytica TISTR 5151. BSG hydrolysate gave higher biomass than SYC hydrolysate possibly due to a higher content of suitable sugars for cell growth. Among three yeasts, T. spathulate JU4-57 gave the highest lipid yields of 62.9 ± 5.67 and 39.9 ± 0.62 mg/g-substrate on BSG and SYC hydrolysates, respectively. This study may contribute greatly to low-cost production of oil sources for biodiesel production and may help to increase the environmental and economic sustainability of the brewery business.
The photoassisted degradation of the recalcitrant and persistent Flubendiamide insecticide was examined in the presence of the metal-oxide semiconductor Ga2O3 in air-equilibrated and inert conditions (Ga2O3/air and Ga2O3/N2, respectively) under Ultraviolet C (UVC) irradiation at 254 nm; for comparison, the degradation of this insecticide was also investigated in catalyst-free/air and catalyst-free/N2 under UVC irradiation. The time course of the degradation was monitored by examining the yields of inorganic ions formed (fluoride, iodide, sulfate, nitrate and ammonium ions) and analyzed quantitatively by ion chromatographic techniques. Mechanistic considerations are described from calculating partial charges and electron densities on each of the functionalities in the Flubendiamide structure in aqueous media. Reactive oxygen species, such as the electrophilic •OH radicals and singlet oxygen, are inferred to attack the insecticide at positions where the functional groups possess the highest electron densities and highest negative partial charges, which led ultimately to defluorination, deiodination, desulfonation, and denitrogenation (i.e., formation of ammonium and nitrate ions). The total yields of decomposition followed expectations in the increasing order: N2 < Ga2O3/N2 < air < Ga2O3/air.
Reverse osmosis (RO) plays an outstanding role in water desalination worldwide. Performance of this technique depends on membrane fouling and the raw water seasonal variations, especially temperature and raw water salt concentration. Hence, to neutralize the impact of temperature and feed concentration on the performance parameters, the data collected from the brackish surface water plant were standardized through the use of the American Society for Testing and Materials methods. The value of this normalization is to be able to discern the performance variation which is due to the membrane aging and the membrane fouling, scaling or degradation. The present research investigates the real industrial results gathered from the first experience of brackish surface water demineralization by RO in Morocco. The results obtained evidently show that the feed water is subject to serious seasonal variations in terms of feed temperature and feed salts concentration, which noticeably affect the feed pressure, membrane permeability, and permeate conductivity. The standardized permeate flow, standardized pressure drop, and standardized salt passage show that the performance of the plant was steady all over the period of the monitoring and the observed performance decline-was due to membrane fouling.