Process optimization for treatment of methyltin mercaptide effluents using modified semi-coke

The central composite process optimization was performed by response surface methodology technique using a design for the treatment of methyltin mercaptide with modified semi-coke. The semi-coke from the coal industry was suitably modified by treating it with phosphoric acid, with a thermal activation process. The objective of the process optimization is to reduce the chemical oxygen demand （COD） and NH4＋-N in the methyltin mercaptide industrial effluent. The process variables considered for process optimization are the semi-coke dosage, adsorption time and effluent pH. The optimized process conditions are identified to be a semi-coke dosage of 80 g/L, adsorption time of 90 min and a pH value of 8.34. The ANOVA results indicate that the adsorbent dosage and pH are the significant parameters, while the adsorption time is insignificant, possibly owing to the large range of adsorption time chosen. The textural characteristics of modified semi-coke were analyzed using scanning electron microscopy and nitrogen adsorption isotherm. The average BET surface area of modified semi-coke is estimated to be 915 mE/g, with the average pore volume of 0.71 cm3/g and a average pore diameter of 3.09 nm, with micropore volume contributing to 52.36%.

Study on the Removing Nitrogen and Phosphorus from Wastewater by Chlorella

[Objective] The aim was to research Chlorella properties in removing ni- trogen and phosphorus from wastewater. [Method] The effects of initial NH4＋-N and total P concentrations, N-to-P ratios, lightJdarkness ratios and pH on the removal of NH4＋-N and total P were evaluated. [Result] The results showed that Chlorella al- most removed NH4＋-N and total P at 100% as initial concentrations of NH4＋-N and total P were no more than 55 and 7 mg/L, respectively, whereas the removal ratio of NH4＋-N decreased to 90% with initial NH4＋-N concentration coming up to 75 mg/L. With N-to-P ratios of 5：1, 10：1 and 25：1, Chlorella completely removed NH4＋-N within 4 d, while the removal ratio of total P reached almost 100% within 7 d, with different N-to-P ratios. With L./D ratios of 24 h： 0 h and 12 h： 12 h as well as the initial concentrations of NH4＋-N at 30 mg/L and total P at 7 mg/L, the removing ra- tio of NH4＋-N and total P almost achieved 100% by Chlorella, and the removing ra- tio under L/D ratio of 24 h：0 h proved much faster. The optimal pH range for Chlorella to remove NH4＋-N and total P was 7-8. [Conclusion] The research pro- vides references for wastewater treatment in biological way and highly-efficient and environment-friendly treatment in future.

Influencing Factors of Ammonium Nitrogen Removal by Composite Phosphate and Magnesium

It is necessary to adjust reaction pH when a single kind of PO4^3- is used as phosphorus source to remove NH4^＋- N in a chemical precipitation process. However, this tedious step could be avoided in experiments that use the buffering effect of the composite phosphate and employ PO4^3- and HPO4^2- as phosphorus sources, pH was controlled by properly changing the proportion of PO4^3- to HPO4^2-. The influences of pH, material proportion and different addition modes of magnesium on NH4^＋-N removal efficiency were investigated, with NH4^3--N concentration in influent being 200 mg/L. It showed that the ratio of HPO4^2- ： PO4^3- was concerned with phosphorus and NH4^＋-N removal. Under the condition that the total amount of phosphate is definite, the removal efficiency of NH4^＋-N decreased with the enhancement of HPO4^2- concentration, while the efficiency of phosphorus increased. When increasing PO4^3- concentration, it benefited the removal of NH4^＋-N, but the remaining phosphorus was high. The results showed that NH4^＋-N concentration decreased from the initial 200 mg/L to 39.14 mg/L with the remaining PO4^3- at 5.14 mg/L if the ratio of HPO4^2- ： PO4^3- remained at 1：3.