The presence of excess nutrients in water resources can be harmful to human health and aquatic ecosystems. To develop an affordable water treatment method, the agricultural waste material coconut husk was converted into a low-cost adsorbent by thermal conversion to biochar, pelletized without (CH), and with chitosan (CHC), or eggshell powder (CHEG) modifications. The physical and chemical properties of all adsorbents were characterized using Brunauer-Emmett-Teller (BET) surface analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, pH_zpc, iodine number and elemental analysis. The adsorption of ammonium (NH₄⁺), nitrate (NO₃⁻), and phosphate (PO₄³⁻) in single and mixed solute solutions was investigated for initial concentrations of 10 mg L^− 1. Langmuir, Freundlich, Sips, Dubinin-Radushkevich (D-R) and BET isotherm models were used to investigate the adsorption mechanisms. The maximum adsorption capacity of NH₄⁺ on CH, CHC, and CHEG from mixed solute solution was 5.0, 4.7 and 5.9 mg g^− 1, respectively, while the adsorption capacity of mixed:single solute solution was 0.95, 0.93, and 1.04, respectively. CH, CHC, and CHEG had greater ability to remove the cation NH₄⁺ than anions NO₃⁻ and PO₄³⁻ from aqueous solution. The highest maximum adsorption capacity for anions NO₃⁻ and PO₄³⁻ was found on CHEG (1.7 mg g^− 1) and CH (6.7 mg g^− 1), respectively. NH₄⁺ and NO₃⁻ were bound by chemisorption as indicated by D-R isotherm E values (> 8 kJ mol^− 1), and enthalpy ∆H values (> 80 kJ mol^− 1). In contrast, PO₄³⁻ adsorption was mainly by physical interaction, including pore-filling, and electrostatic attraction. Pseudo first order and pseudo second order models provided good fits of the sorption kinetics data (R² > 0.9). The initial concentrations of NH₄⁺, NO₃⁻, and PO₄³⁻ in surface water sampled from a canal in Bangkok were 10.4, 1.2, and 3.9 mg L^− 1, respectively, which indicated eutrophication. At a dose of 20 g L^− 1, CHC achieved the best nutrient removal from this surface water, by 24% for NH₄⁺, 25% for NO₃⁻, and 66% for PO₄³⁻ after 48 h contact, respectively.

Potassium permanganate-modified bamboo biochar (MBB) was used to adsorb manganese from simulated groundwater and its performance was compared to that of unmodified bamboo biochar (BB), activated carbon, and manganese greensand. The adsorption kinetics, adsorption isotherms, and manganese fractions were investigated. The Langmuir model was the best fit for manganese adsorption by MBB and BB at the maximum adsorption capacities of 21.277 and 0.803 mg g⁻¹, respectively. The heat of adsorption from the Temkin model indicated that manganese adsorption occurs via an ion exchange process for MBB and a physical adsorption process for BB. The sequential extraction results revealed that manganese was strongly bound to the iron/manganese oxide fraction, in accordance with the chemical adsorption established in pseudo-second order kinetic data records.

This research studied the production of ethanol from desizing wastewater of dye-bleaching industry by using co-culture of Bacillus subtilis D (B) and Saccharomyces cerevisiae TISTR 5160 (S). This work began with the study of the growth of single culture of B and S in wastewater by varying incubation temperature. The optimum temperature for the growth of B and S was 37°C and 30°C, respectively. For co-culture, the order of S inoculation, the inoculum ratio of B to S, shaking effect, incubation temperature after S addition, and the effect of nitrogen sources were studied. The optimum condition for ethanol production of co-culture was shaking at 150rpm and 37°C with the inoculation of B 1 day before S and the inoculum ratio of B to S was 5:10. This gave the ethanol content of 5.8g/L after 48h. Addition of nitrogen sources prolonged the period the ethanol production going to the maximum

Currently, heavy metal-contaminated groundwater is an environmental concern. This study investigated the use of bamboo biochar, chitosan-impregnated biochar, and iron-impregnated biochar for arsenic, iron, and manganese removal from groundwater. Isotherms of arsenic, iron, and manganese adsorption by bamboo derived biochar were compared with those of commercial activated carbon in simulated groundwater composed of single and trinary heavy metal solutions. The binding of heavy metals by virgin and loaded bamboo biochar and activated carbon was also investigated by sequential extraction. Chitosan and iron-impregnated biochar had enhanced arsenic adsorption, but these sorbents turned the pH of solution acidic, while it was alkaline for activated carbon. Adsorption equilibrium times of arsenic and iron were faster for single than trinary heavy metal systems because less ion competition occurred at active sites. The Langmuir model fitted the adsorption data well. The maximum adsorption capacities of arsenic, iron, and manganese by bamboo biochar in trinary heavy metal system were 2.2568, 0.6393, and 1.3541 mg g⁻¹, respectively. The main mechanism for arsenic removal was precipitation with iron. Bamboo biochar bound iron in organic and sulfide fractions and manganese with iron-oxide. Bamboo biochar can replace activated carbon as a more efficient and sustainable carbonaceous sorbent material for removal of mixed heavy metals from groundwater within acceptable pH ranges.

Mangrove biochar residue was used for nitrogen adsorption and retention in sediment, which is beneficial for plant germination. The present study investigated the effect of contact time (5–360 min), biochar dosage (0.2–2 g L⁻¹), pH (5–6), and initial concentration (2–10 mg L⁻¹) on NH₄⁺-N and NO₃⁻-N adsorption. Three different adsorption isotherm models were used to fit the experimental data. Column leaching experiments were conducted to investigate the effect of biochar with sediment from a shrimp pond on nitrogen leaching at varying biochar dosages (0–8% w/w). The results showed that the maximum percentage of both NH₄⁺-N and NO₃⁻-N adsorption was achieved at an equilibrium contact time of 240 min, with an adsorbent dosage of 2 g L⁻¹, and pH at 5.5 and 5, respectively. The adsorption of NH₄⁺-N and NO₃⁻-N were fitted to the Freundlich model and the adsorption process followed the physisorption and ion exchange. The addition of 8% biochar reduced both cumulative water volume and nitrogen leaching from the sediment. The biochar amendment increased the relative abundance of nitrifying and denitrifying bacteria in the sediment. This result suggested that biochar amended with sediment could be useful for nitrogen loss reduction.