Wastewater treatment by the HCR‐process

The increasing requirements in wastewater treatment have led to the development of new wastewater treatment processes based on the know‐how and experience in reaction and process engineering of the chemical industry. Due to their compactness, closed operation and high flexibility, these new processes show a large potential for process integration and significant cost reduction in particular for highly polluted industrial wastewaters. This paper discusses the HCR (h igh‐performance c ompact r eactor) ‐ process, developed at the Mass Transfer Laboratory of the Technical University of Clausthal within the last decade. This process has been realized in more than 30 technical applications with a volume loading of up to 70 kg COD/m³ d and an energy consumption of about 0.4 kWh per kg COD_elim.     

Production of hydrogen from domestic wastewater in a pilot-scale microbial electrolysis cell

Addressing the need to recover energy from the treatment of domestic wastewater, a 120-L microbial electrolysis cell was operated on site in Northern England, using raw domestic wastewater to produce virtually pure hydrogen gas (100?±?6.4 %) for a period of over 3 months. The volumetric loading rate was 0.14 kg of chemical oxygen demand (COD) per cubic metre per day, just below the typical loading rates for activated sludge of 0.2–2 kg?COD?m^?3?day^?1, at an energetic cost of 2.3 kJ/g?COD, which is below the values for activated sludge 2.5–7.2 kJ/g?COD. The reactor produced an equivalent of 0.015 L?H₂?L^?1?day^?1, and recovered around 70 % of the electrical energy input with a coulombic efficiency of 55 %. Although the reactor did not reach the breakeven point of 100 % electrical energy recovery and COD removal was limited, improved hydrogen capture and reactor design could increase the performance levels substantially. Importantly, for the first time, a ‘proof of concept’ has been made, showing that this technology is capable of energy capture as hydrogen gas from low strength domestic wastewaters at ambient temperatures.     

Studies on the survival of enterohemorrhagic and environmental Escherichia coli strains in wastewater and in activated sludges from dairy sewage treatment plants

Survival of Escherichia coli O157:H7 strain isolated from milk in Poland and an environmental E. coli strain in wastewater from Garwolin and ?owicz dairies and in activated sludges from dairy sewage treatment plants as well as in dairy wastewater with activated sludges was examined. Environmental materials were contaminated with about 10(8) of target bacteria/ml of sample. The experiments were performed under temperature conditions typical of autumn-winter (6 degrees) and spring-summer (24 degrees C) seasons. It was found that the non-pathogenic E. coli strain survived longer in all media than the enterohemorrhagic serotype. E. coli O157:H7 bacteria were not detected (in direct plating method) in activated sludges after 21-28 days; in dairy wastewater as well as in wastewater with activated sludges after 21-25 days. These periods for environmental E. coli strain were 35-42 days (activated sludges), 25-28 days (wastewater with activated sludges). At higher temperature environmental E. coli were not detected in wastewater from ?owicz dairy sewage treatment plant after 25 days, but the bacteria were still present in wastewater from Garwolin dairy sewage tratment plant after 34 days. The obtained results show that the lack of environmental E. coli bacteria (as a indicator bacteria of fecal contamination) in dairy wastewater and in dairy wastewater with activated sludges could indicate the absence of pathogenic E. coli bacteria. Prolonged existence of the enterohemorrhagic serotype in activated sludges shows the need to treat activated sludges prior to the utilization of these materials as fertilizer.     

Isolation and Characterization of Pseudomonas sp. Strain ONBA-17 Degrading o-Nitriobenzaldehyde

Aerobic bacteria degrading o-nitrobenzaldehyde (ONBA) were isolated from activated sludges. One of the isolates, ONBA-17, was identified as Pseudomonas sp. The isolate could grow on ONBA as its sole source of carbon and nitrogen. Further studies demonstrated that the strain was a moderately halophilic bacterium and capable of degrading benzoic acid, 2-nitrophenol, 2-aminophenol, 4-hydroxybenzoic acid, and 4-dimetylaminobenzaldehyde. It could completely degrade 100 mg L⁻¹ ONBA at a range of pH 6–8 in 48 h at 30°C, and up to 400 mg L⁻¹ after 288 h. The strain showed potential to be a good candidate for biotreatment of industrial wastewaters containing ONBA due to its salt-tolerance ability, multiresistance to some heavy metals and antibiotics, and the abilities of degradation of aromatic compounds. These findings may help in developing a process for ONBA-containing industrial wastewater treatment.     

Phenol-mediated improved performance of active biomass for treatment of distillery wastewater

Activated sludge from a wastewater treatment plant consists of a consortium of microbes that utilize various organic molecules including persistent organic pollutants for their survival. Phenolic compounds and their derivatives along with dibenzofuran (DBF) are found as dominating pollutants in distillery waste. The acclimatization process leads to selective enrichment of the microbial community; and in this study, we report the acclimatizing effect of phenol on improving the treatment efficiency of two different distillery sludges—sludge from conventional aeration tanks (CAT), and from an extended aeration tank (EAT). The adaptation-dependent performance of activated biomass was studied by monitoring the increase in colony-forming units (CFUs) on mineral media and the utilization pattern for phenol (300×10³ and 530×10³ CFU for CAT and EAT sludge, respectively) and DBF (260×10³ and 430×10³ CFU for CAT and EAT sludge, respectively). The study showed that the acclimatization process remarkably improved the performance sludge for treatment of distillery wastewater. There was an improvement in chemical oxygen demand (COD) removal efficiency from 19% (unacclimatized sludge) to 31% in the case of acclimatized sludge (raw wastewater), which improved further to 82% and 87% with dilution of wastewater by 10 times (0.1×) and by 50 times (0.02×), respectively. Highest growth yields were observed with 0.1× wastewater (0.324 and 0.308 g g⁻¹ d⁻¹ for CAT and EAT sludges, respectively), while lower values are reported for the remaining two forms of wastewater. The study proposes that acclimatization step could be included as part of a treatment plant where the activated biomass could be intermittently metabolically charged by exposing it to selected molecules to increase treatment efficiency.     

Life Cycle Assessment of Urban Wastewater Reclamation and Reuse Alternatives

Continuous population growth is causing increased water contamination. Uneven distribution of water resources and periodic droughts have forced governments to seek new water sources: reclaimed and desalinated water. Wastewater recovery is a tool for better management of the water resources that are diverted from the natural water cycle to the anthropic one. The main objective of this work is to assess the stages of operation of a Spanish Mediterranean wastewater treatment plant to identify the stages with the highest environmental impact, to establish the environmental loads associated with wastewater reuse, and to evaluate alternative final destinations for wastewater. Tertiary treatment does not represent a significant increment in the impact of the total treatment at the plant. The impact of reclaiming 1 cubic meter (m³) of wastewater represents 0.16 kilograms of carbon dioxide per cubic meter (kg CO₂/m³), compared to 0.83 kg CO₂/m³ associated with basic wastewater treatment (primary, secondary, and sludge treatment). From a comparison of the alternatives for wastewater final destination, we observe that replacing potable water means a freshwater savings of 1.1 m³, whereas replacing desalinated water means important energy savings, reflected in all of the indicators. To ensure the availability of potable water to all of the population—especially in areas where water is scarce—governments should promote reusing wastewater under safe conditions as much as possible.     

Efficacy of microalgae for industrial wastewater treatment: a review on operating conditions,treatment efficiency and biomass productivity

Sustainable, clean, renewable energy without negotiating contiguous environment is a challenging task mainly comprises of natural resource management which involves operational efficiency, waste minimisation and energy recovery. Disposal of untreated industrial wastewater with chemical nutrients especially compounds containing nitrogen and phosphorous lead to eutrophication and related environmental issues that affect the recycling processes of bio system. Biotransformation of pollutants using microalgae has proven to be proficient and economic method of wastewater treatment due to their adaptability of growing in various wastewater streams and also useful in the process of CO₂ fixation. Moreover this technology has the competence of producing bio fuels as an alternative energy resource in the form of bio diesel, bio ethanol and biogas. In this review paper, the applicability of microalgae cultivation in industrial wastewater treatment has been discussed extensively including the processes involved, influencing operational parameters such as study mode, cultivation mode and time, method of aeration, pH and intensity of light. Further, the cultivation methods, harvesting techniques involved in the treatment process have been presented. In addition, the analysis on removal efficiency of algal treatment, biomass productivity and lipid content of the cultivated biomass has been discussed widely which possibly will be helpful in adopting the process integration in industrial wastewater treatment with bio energy production.     

中国城市污泥有机质及养分含量与土地利用

土地利用是城市污泥的重要处理处置方法,其有机质和养分含量是土地利用中很受关注的问题。关于中国的城市污泥虽然已有不少研究报道,但不同研究结果之间结论并不一致,且缺乏系统的总结。通过系统搜集了20世纪80年代以来全国城市污泥相关的文献资料,重点评述中国城市污泥的有机质含量及其土地利用问题。通过29个城市污泥组成的统计分析发现,中国城市污泥(不包括工业污泥)的有机质平均含量达到384g／kg,全氮、全磷和全钾分别为27、14．3和7g／kg;有机质、全氮、全磷比纯猪粪分别高出1／3～2／3,但全钾比纯猪粪低1／3。中国城市污泥的有机质含量呈逐年增加的趋势,但氮、磷含量变化规律不明显。研究证明,城市污泥在粮食作物、蔬菜、经济作物及园林绿地上使用,具有明显的肥效和改良土壤的效果。近年来,城市污泥中重金属含量越来越低,这有利用促进城市污泥的土地利用,但中国在有机污染物和病原体的危害方面研究相对较少,对城市污泥土地利用的潜在风险仍缺乏长期的定位试验研究。     

Nitrogen removal performance using anaerobic ammonium oxidation at low temperatures

An anaerobic ammonium oxidation (anammox) process for ammonia-rich wastewater treatment has not been reported at temperatures below 15 degrees C. This study used a gel carrier with entrapped anammox bacteria to obtain a stable nitrogen removal performance at low temperatures. In a continuous feeding test, a high nitrogen conversion rate (6.2 kg N m(-3) day(-1)) was confirmed at 32 degrees C. Nitrogen removal activity decreased gradually with decreasing operation temperature; however, it still occurred at 6 degrees C. Nitrogen conversion rates at 22 and 6.3 degrees C were 2.8 and 0.36 kg N m(-3) day(-1), respectively. Moreover, the stability of anammox activity below 20 degrees C was confirmed for more than 130 days. In batch experiments, anammox gel carriers were characterized with respect to temperature. The optimum temperature for anammox bacteria was found to be 37 degrees C. Furthermore, it was clear that the temperature dependence changed at about 28 degrees C. The apparent activation energy in the temperature range from 22 to 28 degrees C was calculated as 93 kJ mol(-1), and that in the range from 28 to 37 degrees C was 33 kJ mol(-1). This value agrees with the result of a continuous feeding test (94 kJ mol(-1), between 6 and 22 degrees C). The nitrogen removal performance demonstrated at the low temperatures used in this study will open the door for the application of anammox processes to many types of industrial wastewater treatment.     

Microbial cell immobilization in biohydrogen production: a short overview

The high dependence on fossil fuels has escalated the challenges of greenhouse gas emissions and energy security. Biohydrogen is projected as a future alternative energy as a result of its non-polluting characteristics, high energy content (122?kJ/g), and economic feasibility. However, its industrial production has been hampered by several constraints such as low process yields and the formation of biohydrogen-competing reactions. This necessitates the search for other novel strategies to overcome this problem. Cell immobilization technology has been in existence for many decades and is widely used in various processes such as wastewater treatment, food technology, and pharmaceutical industry. In recent years, this technology has caught the attention of many researchers within the biohydrogen production field owing to its merits such as enhanced process yields, reduced microbial contamination, and improved homogeneity. In addition, the use of immobilization in biohydrogen production prevents washout of microbes, stabilizes the pH of the medium, and extends microbial activity during continuous processes. In this short review, an insight into the potential of cell immobilization is presented. A few immobilization techniques such as entrapment, adsorption, encapsulation, and synthetic polymers are discussed. In addition, the effects of process conditions on the performance of immobilized microbial cells during biohydrogen production are discussed. Finally, the review concludes with suggestions on improvement of cell immobilization technologies in biohydrogen production.     

Persistence of poliovirus 1 during the freezing-thawing of hydroxide sludges from a water treatment plant under laboratory conditions

Summary Freezing and thawing of ferric hydroxide sludges from a water treatment plant may be a solution to the problem of disposing of such sludges. It is an excellent method of dewatering. With the loss of hydrated water and extensive modification of the flocs, the risk of desorption of viral particles decreases. Moreover, when sludges are thickened (solids concentration up to 20 g/l), the number of cycles necessary for viral inactivation is reduced from five to three. However, the residues obtained from sludges treated by lagooning or industrial freezing with only one cycle always carry a risk of virologic pollution.     

Selection and adaptation of a phenol-degrading strain ofPseudomonas

Summary Phenol-degrading strain QT 31 ofPseudomonas sp. was selected among other phenol-resistant bacteria from activated sludges of wastewater treatment plant of an oil refinery. Its capacity of degradation was studied at different periods of adaptation, reaching a phenol biodegradation rate of 28 mg/l phenol per hour, from minimal, medium with 1000 mg/l phenol, after adaptation for 20 days.     

Energy expenditure in relation to activity of lesser mouse deer (Tragulus javanicus)

Heat production (HP) of male and female mouse deer during eating, standing and sitting was determined using the open circuit respiration chamber (RC). The time taken for similar activities was also determined in an outdoor enclosure (OD). The animals were fed kangkong (Ipomoea aquatica), sweet potato (Ipomoea batatas) and rabbit pellet ad libitum. Male mouse deer consumed more dry matter (DM), organic matter (OM) and gross energy (GE) than female. The time for each activity of male and female mouse deer kept in RC and OD was similar. The average time spent in RC and OD for both male and female, respectively, for sitting (956 and 896 min/day) was significantly (P<0.01) longer than standing (463 and 520 min/day) and eating (21 and 24 min/day). Heat production for male and female mouse deer, respectively, during eating was the highest (0.44 and 0.43 kJ/kg W^0.75/min) followed by standing (0.37 and 0.33 kJ/kgW^0.75/min) and sitting (0.26 and 0.26 kJ/kg W^0.75/min). The difference in HP per min during standing between male and female was significant (P<0.05). The HP for 08.00–14.00 h and 14.00–20.00 h periods were higher than 20.00–02.00 h and 02.00–08.00 h periods. The overall HP for males during 08.00–14.00 h and 14.00–20.00 h periods were significantly (P<0.05) higher (114.8 and 119.2 kJ/kg W^0.75) than female (107.5 and 110.4 kJ/kg W^0.75), respectively.     

Quantification of the water,energy and carbon footprints of wastewater treatment plants in China considering a water–energy nexus perspective

Water and energy are closely connected and both are very important for human development. Wastewater treatment plants (WWTPs) are central to water–energy interactions as they consume energy to remove pollutants and thus reduce the human gray water footprint on the natural water environment. In this work, we quantified energy consumption in 9 different WWTPs in south China, with different treatment processes, objects, and capacities. The energy intensity in most of these WWTPs is in the range of 0.4–0.5 kWh/m³ in 2014. Footprint methodologies were used in this paper to provide insight into the environmental changes that result from WWTPs. A new indicator “gray water footprint reduction” is proposed based on the notion of gray water footprint to better assess the role of WWTPs in reducing human impacts on water resources. We find that higher capacity and appropriate technology of the WWTPs will result in higher gray water footprint reduction. On average, 6.78 m³ gray water footprint is reduced when 1 m³ domestic sewage is treated in WWTPs in China. 13.38 L freshwater are required to produce the 0.4 kWh electrical input needed for treating 1 m³ domestic wastewater, and 0.23 kg CO₂ is emitted during this process. The wastewater characteristics, treatment technologies as well as management systems have a major impact on the efficiency of energy utilization in reducing gray water footprint via these WWTPs. The additional climate impact associated with wastewater treatment should be considered in China due to the enormous annual wastewater discharge. Policy suggestions are provided based on results in this work and the features of China's energy and water distribution.     

Upgrading of Existing Municipal Wastewater Treatment Plants with the “Non‐Conventional Low MLSS MBR Technology”

In the future, upgrading of existing wastewater treatment plants (wwtps) will be more important than the erection of entirely new plants, as most of the plants necessary in Germany already exist. Thus far, membrane bioreactor (MBR) technology is not used as an alternative for plant upgrading in Germany. However, at several locations the preconditions indicate that the application of the MBR technology for upgrading of plants may be favorable. These preconditions include the need for a substantial enlargement of the aeration tank volume and/or the need to improve the efficiency of the final sedimentation tanks, and also require that the existing tanks be in a good state, so that the tanks can be used in the future. The relevant preconditions and the basic upgrading concept using the MBR technology were presented earlier. Depending on the local preconditions regarding the existing tank volume, a specific aspect of this application can be an operation mode using “non‐conventional low MLSS (mixed liquor suspended solids) concentrations” (5 kg MLSS/m³ through 7 kg MLSS/m³) due to the amount of the existing tank volume. Two research projects were carried out covering the operation of five pilot plants on a cubic meter scale to demonstrate the feasibility of this kind of MBR process. This paper presents the core results of this research work.     

Quinone profiling of bacterial communities in natural and synthetic sewage activated sludge for enhanced phosphate removal

Respiratory quinones were used as biomarkers to study bacterial community structures in activated sludge reactors used for enhanced biological phosphate removal (EBPR). We compared the quinone profiles of EBPR sludges and standard sludges, of natural sewage and synthetic sewage, and of plant scale and laboratory scale systems. Ubiquinone (Q) and menaquinone (MK) components were detected in all sludges tested at molar MK/Q ratios of 0.455 to 0.981. The differences in MK/Q ratios were much larger when we compared different wastewater sludges (i.e., raw sewage and synthetic sewage) than when we compared sludges from the EBPR and standard processes or plant scale and laboratory scale systems. In all sludges tested a Q with eight isoprene units (Q-8) was the most abundant quinone. In the MK fraction, either tetrahydrogenated MK-8 or MK-7 was the predominant type, and there was also a significant proportion of MK-6 to MK-8 in most cases. A numerical cluster analysis of the profiles showed that the sludges tested fell into two major clusters; one included all raw sewage sludges, and the other consisted of all synthetic sewage sludges, independent of the operational mode and scale of the reactors and the phosphate accumulation. These data suggested that Q-8-containing species belonging to the class Proteobacteria (i.e., species belonging to the beta subclass) were the major constituents of the bacterial populations in the EBPR sludge, as well as in standard activated sludge. Members of the class Actinobacteria (gram-positive bacteria with high DNA G+C contents) were the second most abundant group in both types of sludge. The bacterial community structures in activated sludge processes may be affected more by the nature of the influent wastewater than by the introduction of an anaerobic stage into the process or by the scale of the reactors.     

Bioelectrochemical conversion of waste to energy using microbial fuel cell technology

Numerous traditional methods are available for the conversion of waste to energy (WTE) such as incineration, anaerobic digestion, pyrolysis, gasification. Most of them suffer from low efficiency and high energy requirements. Microbial fuel cell (MFC) technology is an excellent alternative for the generation of renewable and sustainable energy and has the potential to help alleviate the current global energy crisis. The total wastewater generated in India is almost 250% of the total treatment capacity, and the Government is, therefore, looking for a sustainable solution for the treatment of waste. Indian population consumes around 700 billion cubic meters of water annually, and this figure will rise to 950 and 1422 billion m³ by 2025 and 2050 respectively. Although treatment of wastewater is a serious concern, the energy recovery potential of wastewater has not yet been fully developed. A survey has been conducted through this study, and it was estimated that MFC technology has the potential to generate around 23.3 and 40 Tera Watt (TW) power by 2025 and 2050 by treating wastewater generated throughout India (urban areas) if utilized properly. This review article presents a various aspect of MFC technology for a proper understanding by the readers. This will be a unique study wherein the energy recovery potential of the wastewater produced in the Indian subcontinent has been estimated through MFC technology. A number of factors affecting the performance of MFC such as electron losses, reactor configuration, and varying concentration must be taken into account to augment output energy. The article summarizes an extensive literature survey of some selected papers published in the last decade.     

15N-Harnstoffumsatz bei Schafen nach Verabreichung in gelöster Form

Two slaughter experiments were carried out to determine whether the protein content of the diet has an influence upon the efficiency of utilization of ME in fast growing chickens. A normal‐protein diet (NPD, 204 g CP/kg DM; 14.7 MJ ME/kg DM) based on soybean meal as the sole source of protein was given at four different levels of intake (ad libitum or restricted at about 90, 65 and 40% ad lib) to 10‐d‐old animals for 2 weeks. In a parallel experiment the chickens were fed ad libitum a low protein diet (LPD, 66 g CP/kg DM; 15.0 MJ ME/kg DM) based on soybean meal. The intake of metabolizable energy ranged from 1675 to 777 and 1770 to 832 kJ/kgW^0.75 per day for NPD and LPD treatments, respectively. Mean values of energy retention, gross efficiency of energy utilization and energy retained as protein were significantly (P<. 05) lower and heat production (expressed as both kJ/kgW^0.75 per day and kJ/kg body protein content^0.75 per day) was significantly higher (P < .05) for the chickens fed on LPD. These findings support the concept of dietary‐induced thermogenesis in response to reductions in dietary protein concentration. It is concluded that the increased heat production found in the birds fed on the low‐protein diet can be explained by both an increase in energy requirements for maintenance (ME_m) and a sharp decrease in the efficiency of utilization of ME for growth (k₈).     

Biodegradability of tannin-containing wastewater from leather industry

Tannins occur commonly in the wastewaters from forestry, plant medicine, paper and leather industries. The treatment of this kind of wastewaters, including settling and biodegradation, is usually difficult because tannins are highly soluble in water and would inhibit the growth of microorganisms in activated sludge. The objective of this study is to investigate biodegradability of tannin-containing wastewaters, so as to characterize the pollution properties of such wastewaters and provide a reference for their biological treatment in wastewater treatment plants. The research was typified by using the wastewater collected from vegetable tanning process in leather industry. A model was developed to describe the activated sludge process, and the biodegradation kinetics of vegetable tanning wastewater (VET wastewater) was studied. It was found that the biodegradability of tannin-containing wastewater varies heavily with the content of tannins in wastewater. The biodegradation of VET wastewater with tannin content around 4,900 mg/l occurred inefficiently due to the inhibition of tannins to the activated sludge process, and only 34.7% of biodegradation extent was reached in 14 days of incubation. The optimal biodegradability of VET wastewater was observed when its tannin content was diluted to 490 mg/l, where the COD and tannin removals reached 51.3% and 45.1% respectively in 6 days. Hence, it is suggested that a proper control of tannin content is necessary to achieve an effective biodegradation of tannin-containing wastewaters in wastewater treatment plants.