铁盐与阴离子型PAM联合调质处理给水厂排泥水试验研究

采用铁盐与阴离子型PAM联合调质方式对给水厂排泥水进行调质试验.试验条件下,AN910PWG投加率为2‰,铁盐与其投加质量比为1时,调质后污泥絮体颗粒较大,沉速为3.18 mm/s,污泥比阻为4×1011 m/kg,上清液浊度为10 NTU,与阳离子型FO4240SH投加率为4‰时的调质效果相当,但药剂费用节约显著.     

Biodegradation of Mixtures of Phenolic Compounds in an Upward-Flow Anaerobic Sludge Blanket Reactor

The anaerobic biodegradability of mixtures of phenolic compounds was studied under continuous and batch systems. Continuous experiments were carried out in up-flow anaerobic sludge bed (UASB) reactors degrading a mixture of phenol and p-cresol as the main carbon and energy sources. The total chemical oxygen demand (COD) removal above 90% was achieved even at organic loading rates as high as 7 kg COD/m3/day. Batch experiments were conducted with mixtures of phenolic compounds (phenol, p-cresol, and o-cresol) to determine the specific biodegradation rates using unadapted and adapted anaerobic granular sludge. Phenol and p-cresol were mineralized by adapted sludge with rates several orders of magnitude higher than unadapted sludge. Additionally, an UASB reactor was operated with the mixture phenol, p-cresol, and o-cresol. After 54 days of operation, 80% of o-cresol (supplied at 132 mg/L) was eliminated. The phenol biodegradation was not affected by the presence of o-cresol. These results demonstrate that major phenolic components in petrochemical effluents can be biodegraded simultaneously during anaerobic treatment.     

Estimating Solar and Nonsolar Inactivation Rates of Airborne Bacteria

Land application of biosolids is a wide spread practice in the United States, Canada, and Western Europe. Given the potential for biosolid aerosolization during land application, both solar and nonsolar induced inactivation rate information is needed to more accurately predict the fate of bacteria in air. Pilot-scale bioaerosol reactor experiments that independently measure the solar and nonsolar (absence of solar radiation) inactivation rates of airborne Mycobacterium parafortuitum and Escherichia coli were performed. Direct fluorescent microscopy measurements for total airborne bacteria and culture-based assays were used to measure concentrations in a 1?m3 aerosol reactor that was transparent to UV-A and UV-B wavelengths, and to produce decay curves of airborne bacteria under moderate (50–60%) and high (85–95%) levels of relative humidity (RH). E. coli was more susceptible to airborne decay than M. parafortuitum at all RH levels tested. RH strongly influenced solar and nonsolar airborne inactivation rates in both bacteria. These inactivation rates for both bacteria were greatest at moderate RH levels.     

宁德滩涂软土工程特性研究

宁德海域分布深厚淤泥。通过多种勘探手段对宁德滩涂淤泥的研究,查明了该地层的岩土工程特性,探寻了测取其各种地质参数的最佳试验方法和组合,通过对力学参数与深度的规律性研究,总结了采用静力触探推算宁德滩涂淤泥不排水抗剪强度的经验公式,验证了原位测试手段在查找岩土规律性方面的优势,对今后宁德海积软土区域的综合勘探和工程建设有指导意义。     

Low-temperature alkaline pyrolysis of sewage sludge for enhanced H2 production with in-situ carbon capture

Pyrolysis has been recognized as one of the promising thermal technologies on the account of satisfying the principles of waste reduction, resource recovery, and detoxification. This study proposed the alkaline thermal treatment of sewage sludge of enhanced H₂ production and in-situ carbon capture. The maximum H₂ yield of ∼10 mmol g⁻¹ biomass was achieved at 1:3 sludge: NaOH ratio, 10 °C min⁻¹ heating rate, and 500 °C temperature, with the H₂ purity of 79.1% in the gaseous products. The presence of NaOH significantly promoted H₂ production and substantially suppressed CO and CO₂. Temperature also played an important role in cracking of CC and CH bonds and gave H₂-rich gas (H₂ formation rate 0.34 mmol min⁻¹ g⁻¹) with a high yield of 10.3 mmol g⁻¹ at 500 °C. The solid residue analysis via XRD verified the existence of Na₂CO₃ in the solid, implying the inherent carbon management potential of the NaOH during the sludge pyrolysis process.     

Production of hydrogen in a granular sludge-based anaerobic continuous stirred tank reactor

An investigation on biohydrogen production was conducted in a granular sludge-based continuous stirred tank reactor (CSTR). The reactor performance was assessed at five different glucose concentrations of 2.5, 5, 10, 20 and 40 g/L and four hydraulic retention times (HRTs) of 0.25, 0.5, 1 and 2 h, resulting in the organic loading rates (OLRs) ranged between 2.5 and 20 g-glucose/L h. Carbon flow was traced by analyzing the composition of gaseous and soluble metabolites as well as the cell yield. Butyrate, acetate and ethanol were found to be the major soluble metabolite products in the biochemical synthesis of hydrogen. Carbon balance analysis showed that more than half of the glucose carbon was converted into unidentified soluble products at an OLR of 2.5 g-glucose/L h. It was found that high hydrogen yields corresponded to a sludge loading rate in between 0.6 and 0.8 g-glucose/g-VSS h. Substantial suppression in hydrogen yield was noted as the sludge loading rate fell beyond the optimum range. It is deduced that decreasing the sludge loading rate induced the metabolic shift of biochemical reactions at an OLR of 2.5 g-glucose/L h, which resulted in a substantial reduction in hydrogen yield to 0.36–0.41 mol-_H2${\mathrm{H}}_2$/mol-glucose. Optimal operation conditions for peak hydrogen yield (1.84 mol-_H2${\mathrm{H}}_2$/mol-glucose) and hydrogen production rate (3.26 L/L h) were achieved at an OLR of 20 g-glucose/L h, which corresponded to an HRT of 0.5 h and an influent glucose concentration of 10 g/L. Influence of HRT and substrate concentration on the reactor performance was interrelated and the adverse impact on hydrogen production was noted as substrate concentration was higher than 20 g/L or HRT was shorter than 0.5 h. The experimental study indicated that a higher OLR derived from appropriate HRTs and substrate concentrations was desirable for hydrogen production in such a granule-based CSTR.     

Co-combustion of sludge with coal

Utilisation of waste-water sludge is one of the most difficult processes of environment protection because of the high moisture and contents of harmful substances. The waste-water treatment systems in Poland, especially in small towns, are often not separate from industrial sewage systems and this causes relatively large contents of heavy metals and other toxic substances in the sludge. Incineration is the only effective method of utilisation of such waste material. From the other side, coal is still the most popular fuel in Poland, and it is often used in many boilers producing hot water for the central heating of buildings or parts of the towns. Mostly they are stoker fired boilers of old construction, and they need urgent modernisation. The use of stoker-fired boilers for incineration of the sludge in small towns is the object of the analysis presented in this paper. There are two important points in the co-combustion of sludge with coal in a stoker-fired boilers: ecological and exploitation requirements. The important restriction of the sludge/coal ratio is the emission of harmful substances with the flue gas. There are substances originating from the components of the sludge: SO₂, NO_x, HCl, heavy metals and dust. Their concentrations in the flue gas should meet the environmental regulations. The other factor influencing the co-combustion process is the change of physical and thermal properties of the fuel: heating value, moisture content and ash composition. These influence the thermal output of the boiler, the amount of air required for combustion, the volume of flue gases and dust concentration and particle distribution. In this paper, the results of experiments performed with an experimental boiler are presented. The effects of the following parameters are considered: composition and thermal parameters of the sludge and their change during the year, emissions of SO₂, NO_x, CO and dust from the experimental boiler for various compositions of the fuel (sludge/coal ratio, moisture content). As a result of the analysis, the parameters limiting the amount of sludge in a mixture with coal are identified.     

Heat and energy requirements in thermophilic anaerobic sludge digestion

The heating requirements of the thermophilic anaerobic digestion process were studied. Biogas production was studied in laboratory experiments at retention times from 1 to 10 days. The data gathered in the experiments was then used to perform a heat and energy analysis. The source of heat was a conventional CHP unit system. The results showed that thermophilic digestion is much faster than mesophilic digestion and therefore produces more biogas in a shorter time or at smaller digester volumes. The major part of the heating requirements consisted of sludge heating. The heat losses of the digester were only 2–8% of the sludge heating requirements. The heating requirements in thermophilic digestion are about twice those of mesophilic digestion. Therefore a CHP unit system cannot cover all of the needs for successful operation of thermophilic digestion. Heat regeneration was introduced as a solution. Heat is regenerated from the sludge outflow at a temperature of 50–55 °C and transferred to the cold inflow sludge at a temperature of 11 °C. Enough heat is regenerated in a conventional counter flow heat exchanger to bring the thermophilic process to the same level as the mesophilic one. Considering the smaller digester volumes and the relatively small investment in the regenerative equipment, the construction of thermophilic digestion systems may be a very good alternative to conventional mesophilic sludge digestion systems.     

Reduced membrane fouling in a novel bio-entrapped membrane reactor for treatment of food and beverage processing wastewater

A novel Bio-Entrapped Membrane Reactor (BEMR) packed with bio-ball carriers was constructed and investigated for organics removal and membrane fouling by soluble microbial products (SMP). An objective was to evaluate the stability of the filtration process in membrane bioreactors through backwashing and chemical cleaning. The novel BEMR was compared to a conventional membrane bioreactor (CMBR) on performance, with both treating identical wastewater from a food and beverage processing plant. The new reactor has a longer sludge retention time (SRT) and lower mixed liquor suspended solids (MLSS) content than does the conventional. Three different hydraulic retention times (HRTs) of 6, 9, and 12 h were studied. The results show faster rise of the transmembrane pressure (TMP) with decreasing hydraulic retention time (HRT) in both reactors, where most significant membrane fouling was associated with high SMP (consisting of carbohydrate and protein) contents that were prevalent at the shortest HRT of 6 h. Membrane fouling was improved in the new reactor, which led to a longer membrane service period with the new reactor. Rapid membrane fouling was attributed to increased production of biomass and SMP, as in the conventional reactor. SMP of 10-100 kDa from both MBRs were predominant with more than 70% of the SMP <100 kDa. Protein was the major component of SMP rather than carbohydrate in both reactors. The new reactor sustained operation at constant permeate flux that required seven times less frequent chemical cleaning than did the conventional reactor. The new BEMR offers effective organics removal while reducing membrane fouling.