pH Control during the Struvite Precipitation Process of Wastewaters

Abstract The high concentration of phosphorus and nitrogen in wastewater and sludge could be lowered to a certain level by struvite (MgNH4PO4•6H2O) crystallization. One of the main factors for struvite formation is the solution pH. It can be adjusted by non-reagent carbon (CO2) dioxide stripping through the process of aeration. The intensity of the mass transfer between the air and the supernatant of dewatering sludge obtained from wastewater treatment plant is characterized by the volumetric liquid-side mass transfer coefficient, which can be estimated theoretically. It is found that the rate of pH increase depends strongly on the sparging area of the air distribution system while the air flow rate does not influence considerably the Dissolved Oxygen (DO) level which governs the CO2 stripping process. The theoretical calculated values of the volumetric mass transfer coefficient have been compared with those obtained experimentally. Based on the data obtained, relationships of pH/kLa (mass transfer coefficient) were developed. These correlations serve as a tool for prediction of pH during the struvite precipitation process

Phosphorus Recovery through Waste Transformation: Implication for an Alternative Fertilizer

Presently, the recovery and reuse of phosphorus are still far from being a mainstream practice. Yet, the techniques already accepted and applied differ by the origin of the used matter (wastewater, sludge, ash) and are mainly focused on the process of precipitation. One of these techniques is struvite (magnesium ammonium phosphate; MAP; MgNH4PO4·6H2O) precipitation, which can be implemented in wastewater treatment plants that use enhanced biological or semi-biological/chemical phosphorus (P) removal. Struvite/MAP is formed by a basic precipitation reaction in different stages of the wastewater treatment process, where magnesium (Mg2+), ammonium (NH4+), and orthophosphate (PO4−3). This chapter aims to discuss: (i) the progress in extraction of P from sewage sludge and animal manure; (ii) the methods to create optimal conditions for struvite precipitation in such media; (iii) the avenues for overcoming the problems associated with choosing the right Mg source, pH adjustment and the non-acceptable level of organic matter in the initial suspension; and (iv) the implication of struvite as an alternative fertilizer for the global agriculture sector

Does first-trimester serum pregnancy-associated plasma protein A differ in pregnant women with sickle cell disease?

OBJECTIVE: To assess whether levels of first-trimester pregnancy-associated plasma protein A (PAPP-A) differ between women with and without sickle cell disease (SCD). METHODS: Retrospective study of 101 singleton pregnancies in women with SCD (including 55 with genotype HbSS, 37 with genotype HbSC, and nine with other genotypes). Measured levels of PAPP-A were converted to multiple of the median (MoM) values corrected for gestational age and maternal characteristics. Median PAPP-A MoM in the SCD group was compared with that of 1010 controls. RESULTS: In the SCD group median, PAPP-A MoM was lower than in the non-SCD group (0.72, interquartile range [IQR] = 0.54-1.14 versus 1.09, IQR = 0.74-1.49; P < .001). Within the SCD group median PAPP-A MoM was lower for those with genotype HbSS than HbSC (0.62, IQR = 0.44-1.14 versus 0.94, IQR = 0.72-1.25; .006). In 7.3% (4/55) of the HbSS group, there was stillbirth, and in these cases, PAPP-A was less than or equal to 0.5 MoM; in the control group, the incidence of stillbirth was lower (1%; P < .001). In HbSS disease, the incidence of small for gestational age (SGA) neonates was increased. CONCLUSION: Pregnancies with HbSS have lower PAPP-A MoM values and higher incidence of stillbirth and birth of SGA neonates than in non-SCD controls

Laser coagulation in complicated monochorionic pregnancies

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Medicina, Departamento de Obstetricia y Ginecología. Fecha de lectura: 23-05-2018Monochorionic pregnancies are found in 1 in 200 births, but the incidence is increasing because of the widespread use of assisted reproductive technology. Monochorionic twins, compared to dichorionic twins, have a considerably higher risk of pregnancy complications that are dues to the process of splitting of the single embryonic mass [congenital abnormalities, conjoint twins, selective fetal growth restriction (sFGR)] and the communicating placental vessels between the two circulations [twin-to-twin transfusion syndrome (TTTS), twin reversed arterial perfusion (TRAP) sequence, twin anemia polycythemia sequence (TAPS)]. This thesis reports on the outcome of pregnancies with sFGR (with and without superimposed TTTS) treated by endoscopic laser separation of the inter-twin communicating placental vessels. Triplet pregnancies in which two or all three fetuses are monochorionic, are at very high risk of perinatal death. The incidence of dichorionic triamniotic pregnancies has dramatically increased following the practice of IVF with delayed transfer of two embryos. This thesis reports on the outcome of monochorionic and dichorionic triplet pregnancies complicated by TTTS (with and without sFGR) treated by endoscopic laser separation of the communicating placental vessels. The thesis also reports on the development of a first-trimester technique for embryo reduction of one of the two monochorionic twins by ultrasound-guided interstitial laser ablation of the pelvic vessel

Potential Use of Microbial Fuel Cell Technology in Wastewater Treatment

Two options, in regard to applying microbial fuel cells (MFCs) in water treatment, are under discussion, namely the conversion of the chemical energy of organic substrates to electricity, as well as the use their potential to reduce different species, such as the ionic form of copper (Cu2+ converted to metal copper) and iron (Fe3+ converted to Fe2+). The high reduction potential of Cu2+ and Fe3+ makes the processes of electricity production and metal reduction, to be performed simultaneously in MFC, achievable. The electrical yield measurement during the experiments of anodic organic matter degradation by MFC in treating an artificial wastewater with chemical oxygen demand (COD) 0.6 and 1.6 g O2&middot;dm&minus;3, as initial COD, are given. It is demonstrated that the higher organic load is associated with better electrical yield. A comparison of MFC and conventional anaerobic digestion performance is discussed, as well. Experimental proofs of copper removal and phosphate mobilization, following the iron reduction of FePO4, are also reported