Joachim Behrendt

Resources and nutrients oriented greywater treatment for non-potable reuses.

This paper evaluated the performance and suitability of a resources and nutrients oriented decentralized greywater treatment system which uses a submerged spiral wound module. This greywater treatment system is aimed at treating and recovering the resources present in the wastewater. The study revealed that the UF membrane filtration system was able to maintain a permeate flux between 6 and 10 L/m2/h. TOC can be reduced from the influent value of 161 to 28.6 mg/L in the permeate, meaning an average elimination rate of 83.4%. In addition, soluble nutrients such as ammonia and phosphorus can pass through the UF membrane and remain in the permeate. The total nitrogen and total phosphorus in the permeate were 16.7 and 6.7 mg/L respectively. The permeate was low in turbidity (below 1 NTU) and free of suspended solids and E. coli and had an excellent physical appearance. The permeate can be used in gardening and agriculture for irrigation and soil fertilization or alternatively for toilet flushing after disinfection. The retentate generated in this system can be treated with blackwater and kitchen waste in an anaerobic digester at a later stage for producing biogas or compost.

Measuring nitrate concentration in wastewaters with high chloride content

ABSTRACT The presence of chloride ions in wastewaters in concentrations above 50 mg/L poses interference in several methods used for the measurement of nitrate-nitrogen. The aim of this study was to characterise the reliability and costs of some commonly available methods for the analysis of nitrate concentration in landfill leachate which contains high chloride levels. To investigate the effect of chloride interference, several widely used methods [ion chromatography (IC), continuous flow analysis (CFA), the German standard method (DIN), cuvette test (CUV), standard addition method (SAM) and reflectometric test (REF)] were used to measure the nitrate concentration in synthetic solutions containing varying concentrations of chloride and nitrate-nitrogen. Nitrate recoveries of the various methods were found to decrease in the following rank order: CUV (>95%) > IC (>90%) > CFA (89%) > DIN (88%) > REF (70%) > SAM (<80%). In the second part of the study, the same methods were used to measure nitrate concentrations in samples of biologically nitrified landfill leachate with and without chloride elimination. For leachate samples without chloride elimination, CUV results were well correlated (linear regression) with IC results (slope = 1.02/R2 = 0.99) but to lesser extents with results obtained by CFA (0.91/0.86), DIN (0.89/0.97) and REF (0.86/0.77), and not correlated with SAM (0.74/–1.3). The incurred measurement costs per sample (in Euros) for the methods were as follows: CFA (<0.1) < DIN (0.6) < REF (0.7) < SAM (3) < CUV (3.8) < IC (15). Cuvette tests are recommended as the method of choice due to their accuracy and lower cost than IC.

Modeling of aerated upflowed fixed bed reactors for the nitrification

A mathematical model for the nitrification in an aerated fixed bed reactor has been developed. This model is based on material balances in the bulk liquid, gas phase and in the biofilm area. The fixed bed is divided into a number of cells according to the reduced remixing behaviour. A fixed bed cell consists of 4 compartments: the support, the gas phase, the bulk liquid phase and the stagnant volume containing the biofilm. In the stagnant volume the biological transmutation of the ammonia is located. The transport phenomena are modelled with mass transfer formulations so that the balances could be formulated as an initial value problem. The results of the simulation and experiments are compared.

Nanofiltration for safe drinking water in underdeveloped regions – a feasibility study

The fact from the United Nations that in 2015, about 663 million people worldwide did not have access to an improved drinking water source, does not resemble the reality wherein more than 1.8 billion people worldwide were consuming water which is unsafe for drinking. Nanofiltration, with the ability to reject several trace organic compounds, heavy metals and viruses at a lower energy demand than reverse osmosis, has found application for the production of high quality drinking water in developed nations. This study briefly reviewed the efficacy of nanofiltration for drinking water production considering various types of pollutants. Series of experiments were conducted using a pilot-scale nanofiltration unit, to assess the potential for drinking water production, from ground water, in a developing country like Ghana and to estimate the associated costs. The economic feasibility of a micro-enterprise (relying on nanofiltration) was evaluated for tackling the economic water scarcity in a rural area. The concept of micro-enterprise based on a pilot-scale nanofiltration system was found to be suitable for producing adequate quantity of safe drinking water (at a reasonable cost of less than €0.01 per litre) for a village in a developing country. Offering safe and economic drinking water with a possibility for small margins and employment opportunities aiming for poverty alleviation, its operation was found to be economical and sustainable.

Comparison of NF-RO and RO-NF for the treatment of mature landfill leachates: a guide for landfill operators

Reverse osmosis (RO) and nanofiltration (NF) are among the state-of-the-art technologies for treating landfill leachates. Due to the complexity and variance in the composition of leachates, numerous combinations of multiple technologies are used for their treatment. One process chain for the treatment of raw leachate is RO followed by further concentration of RO-retentate using NF (RO-NF scheme). The aptness of this process train used by some landfill sites around the world (usually with the aim of volume reduction so as to re-inject the concentrate into the landfill) is questionable. This study investigated two schemes RO-NF and NF-RO (nanofiltration of raw leachate followed by reverse osmosis of NF permeate) to identify their merits/demerits. Experiments were conducted in bench scale using commercial membranes: DOW Filmtec NF270 and SW30HR. Filtration trials were performed at different pressures to compare the water and solute transports in the individual stages of the two schemes. Based on the water fluxes and compositions of retentates and permeates; osmotic pressures, energy demands, and other possible operational advantages were discussed. NF-RO offers some advantages and flexibility for leachate treatment besides being energy efficient compared to RO-NF, wherein osmotic pressure steadily increases during operation in turn increasing operation and maintenance costs.

The LooLoop-Process: The First “Waterless” Flushing Toilet

The environmentally open disposal of fecal contaminated wastewater flows from flushing toilets has caused and is causing a broad variety of qualitative threats and problems. Additionally, the extraction of freshwater for domestic uses from long-term renewable water resources, like ground water, and the following disposal into short-term renewable water resources, like rivers, which flow finally into the oceans within days up to a few months, is intensifying the decrease of con- tinental fresh water resources. With this de-central concept innovation, most of this threats and problems can be solved, and the water demand for flushing of toilets can be reduced down to zero at the same time. Thereby, a closer look at the different types of buildings is essential to developing specific technologies according to the characteristics and amounts of their partial-stream separated wastewater flows. A characterization of different domestic buildings types is presented in this paper and a holistic approach is introduced, of how to reuse fecal contaminated flows, as well as how to reclaim valuables, like biogas, mineral fertilizer and soil-conditioner by simultaneously eliminating all pathogens and hazardous substances, like phar- maceuticals, hormones and multi-resistance plasmids.

Biologische und Chemische Behandlung Kontaminierter Grundwässer

Kontaminierte Grundwasser sind auf Bodenverunreinigungen zuruckzufuhren, die haufig schon mehrere Jahrzehnte zuruckliegen (Altlasten) und die als Folge von Ablagerungen und Versickerungen, meist organischer Schadstoffe, an Industriestandorten auftreten. Bei der Sanierung dieser Altlasten muβ das Grundwasser hochgepumt und soweit gereinigt werden, daβ es in die Kanalisation oder in den Vorfluter eingeleitet werden kann.

Biological and Chemical Treatment of Contaminated Groundwaters

Contaminated groundwaters are due to soil pollution which are often older than several decades (old loads), and which appear as a consequence of deposite and seepages of mostly organic pollutants at industrial sites. As to the sanitation of such old loads, the groundwater must be pumped up and cleaned in such a way that it can be passed into the drains or the main outfall. Here we can use biological-chemical procedures. Microorganisms tranform the pollutants into carbon dioxide, water and biomass. Persitent substances are partly oxidized by means of ozone so that their biological degradation is improved. Apart from little surplus sludge, no residual substances (precipated sludges, charged activated carbon) are induced by this procedure.