Struvite formation, analytical methods and effects of pH and Ca2+.

Struvite formation is mainly controlled by concentrations of Mg2+, NH4+ and PO4 3+, pH, temperature, and other ions like Ca2+. Experiments evaluating the effects of pH and Ca2+ on struvite formation indicated that XRD is only a qualitative method to analyze the struvite content in precipitating compounds, which was also reflected in microscopic images. The element analyses preceded by a dissolution method were introduced to quantitatively determine the struvite content and were shown to be an efficient enough method. Based on element analyses, the struvite content could be calculated according to the N content in the precipitations, based on the molar ratios (1:1:1) of Mg, N and P in pure struvite (MgNH4PO4 x 6H2O). It was found that the optimal pH ranges for the struvite content >90% were respectively at 7.5 approximately 9.0 with ultra pure water as solute and at 7.0 approximately 7.5 with tap water (mainly consisting of ground water) as solute. Applying a pH > 8.0 in real wastewater containing Ca2+ might result in impure struvite contents in the precipitate due to the effect of Ca2+.

Experimental study on sludge reduction by ultrasound.

In recent years, considerable impetus emerges to develop strategies for reducing excess sludge produced in biological wastewater treatment (BWT) systems. In this study, an experiment on sludge reduction by ultrasound treatment was conducted. The influences of sonication on observed yield, sludge reduction, effluent quality, sludge settleability and stability were extensively evaluated. It was found that ultrasound had an impressive potential to reduce sludge production. Moreover, it was also concluded that a treatment time of 10 minutes was more cost-effective for sludge reduction, and a reduction by 44% was reached with an ultrasonic intensity of 0.25 w/ml. The reduction could be mainly attributed to disintegration of bio-flocs and cryptic growth. In addition, sonication time seemed to be more effective to reduce sludge production compared with ultrasonic intensity. Slight deterioration of the effluent quality and some variations of the sludge settleability and stability were observed after ultrasound treatment.

Model-based evaluation of struvite recovery from an in-line stripper in a BNR process (BCFS).

Phosphate removal and recovery can be combined in BNR processes. This may be realised by struvite precipitation from the supernatant of the sludge in anaerobic compartments. This can be beneficial for either improving bio-P removal effluent quality or lowering the influent COD/P ratio required for bio-P removal. For this reason, a patented BNR process, BCFS, was developed and applied in The Netherlands. Several questions relating to P-recovery and behaviour of the system remain unclear and need to be ascertained. For this purpose, a modelling technique was employed in this study. With the help of a previous developed model describing carbon oxidation and nutrient removal, three cases were fully simulated. The simulations demonstrated that there was an optimal stripping flow rate and P-recovery would increase in costs and bio-P activity might be negatively affected due to decreased bio-P efficiency if this value was exceeded. The simulations indicated that the minimal COD(biod)/P ratio required for the effluent standard (1 g P/m3) could be lowered from 20 to 10 with 36% of P-recovery. A simulation with dynamic inflow revealed that the dynamic influent loads affected slightly the anaerobic supernatant phosphate concentration but the effluent phosphate concentration would not be affected with regular P-recovery.

Model-based evaluation of COD influence on a partial nitrification-Anammox biofilm (CANON) process.

A model evaluating COD influence on a partial nitrification-Anammox biofilm process is integrated on the basis of heterotrophic growth as described in ASM3, combined with a previously published model for the CANON process. This integrated model can simulate the activities of heterotrophs and autotrophs involved in a biofilm, and interactions between COD oxidation, denitrification, nitrification and Anammox can be evaluated. Simulations indicate that COD in the influent has no important influence on the trends in the partial nitrification-Anammox biofilm process. Besides full COD removal, a total nitrogen removal efficiency of about 90% can be expected for stable biofilm systems. Furthermore, Anammox is a major contributor to the total nitrogen removal in stable biofilm systems and conventional denitrification only takes a share of <20% in the total nitrogen removal.

A proposed sustainable BNR plant with the emphasis on recovery of COD and phosphate.

Water problems have to be solved in an integrated way, and sustainability has become a major issue. For this reason, developing more sustainable wastewater treatment processes is needed. New discoveries and good understanding on microbial conversions of nitrogen and phosphorus make more sustainable processes possible. New options for decentralized sustainable sanitation are generally compared to conventional sewage systems, we think that for a proper comparison also innovative centralized treatment schemes should be evaluated. In this article, a more sustainable WWTP is proposed for municipal wastewater treatment, mainly based on the principles of denitrifying dephosphatation and anaerobic ammonium oxidation (ANAMMOX). The proposed system consists of a first stage of the A/B process in which maximal sludge production is achieved. In this way, COD is regained as sludge for methanation. The following BCFS and CANON processes can remove N and P with minimal or no COD need. As a potential fertiliser, struvite can easily be removed from the sludge water by adding magnesium compounds. A case study is done on the basis of the mass balance over the proposed plant. The effluent from the system has a good quality to be recycled. This could also make a contribution to meeting the world's water needs and lessening the impact on the world's water environment. Since all the separate units are already applied or tested on pilot-scale, no problems for technical implementation are foreseen.

Ultrastructural observation on macrophage-lymphocyte interactions in semen from Tripterygium wilfordii Hook.f. takers.

Sixty-nine specimens from Tripterygium Wilfordii Hook.f. (TWH) users were investigated by electron microscopy. No macrophages were demonstrated in the 21 specimens collected prior to the administration of TWH. However, it was found in 23 out of the 48 semen specimens obtained following the TWH administration. The macrophages were functionally active as shown by the presence of a large number of cytoplasmic processes and pseudopodia on the surface, and primary and secondary lysosomes in the cytoplasm. The macrophages phagocytized sperm debris and degenerated or dead spermatids with formation of specific phagosomes. Around those macrophages, lymphocytes were commonly noted. The cytoplasmic processes of the two cell types could come into contact or even fuse with each other, leading to tight junction-like structure; in some of the contacts, the plasma membranes were found dissolved so as to form direct cytoplasmic linkage.