Ralf Otterpohl

Review of the technological approaches for grey water treatment and reuses

Based on literature review, a non-potable urban grey water reuse standard is proposed and the treatment alternatives and reuse scheme for grey water reuses are evaluated according to grey water characteristics and the proposed standard. The literature review shows that all types of grey water have good biodegradability. The bathroom and the laundry grey water are deficient in both nitrogen and phosphors. The kitchen grey water has a balanced COD: N: P ratio. The review also reveals that physical processes alone are not sufficient to guarantee an adequate reduction of the organics, nutrients and surfactants. The chemical processes can efficiently remove the suspended solids, organic materials and surfactants in the low strength grey water. The combination of aerobic biological process with physical filtration and disinfection is considered to be the most economical and feasible solution for grey water recycling. The MBR appears to be a very attractive solution in collective urban residential buildings.

Ryegrass uptake of carbamazepine and ibuprofen applied by urine fertilization.

Human urine is a potential alternative fertilizer for agriculture. However, its usage is associated with a risk of spreading pharmaceutical residues to fields. The individual and combined behavior of carbamazepine and ibuprofen was investigated by GC/MS analysis in a greenhouse experiment using ryegrass fertilized with pharmaceutical-spiked urine. Only carbamazepine could be detected in soil, roots, and aerial plant parts. Fifty-three per cent of carbamazepine originally present in the urine was recovered in soil samples taken after three months. Additionally, 34% of carbamazepine was found in aerial plant parts and 0.3% in roots. Model calculations showed that neither roots nor Casparian strip posed a considerable barrier to uptake. Carbamazepine transport was clearly driven by transpiration. Ibuprofen was not detected in the soil or in any plant parts after three months. This was assumed to be due to biodegradation of ibuprofen. Carbamazepine and ibuprofen, singly or in combination, did not adversely affect the growth of ryegrass.

Comparison of analytical and theoretical pharmaceutical concentrations in human urine in Germany

Urine is considered as a valuable plant fertiliser due to its high nutrient content. However, urine also contains pharmaceuticals. Currently, little is known regarding expected pharmaceutical concentrations in urine and the resulting risks. Through series of analyses in Hamburg and Berlin and results from the development of a concentration prediction model this knowledge gap was intended to be filled. To which extent the theoretical calculations can substitute analyses of pharmaceuticals was also tested. Results showed that the model fits well for bezafibrate, carbamazepine, diclofenac, ibuprofen, phenazone, and pentoxifylline. In Hamburg an R(2) value of 0.98 and in Berlin of 0.90 was achieved for correlations between predicted and analysed concentrations. Additionally, it was shown that a sufficient number of people discharging their urine to the respective collection system are important to allow for reasonable predictions via calculation. Also, comparisons of predicted pharmaceutical concentrations to those determined in other projects showed good correlations. Overall, it can be concluded that in any case the calculated concentrations exceed the measured ones and are therefore conservative. This overestimation can be explained by several factors discussed in this article.

A comparison of human pharmaceutical concentrations in raw municipal wastewater and yellowwater

Currently, many articles report on pharmaceutical residues detected in various compartments of the environment. A major pathway into the aquatic environment is municipal wastewater. This article discusses the relevance of yellowwater (urine) as pharmaceutical source within this wastewater stream. Literature data about concentrations of 28 pharmaceutical residues detected in raw wastewater are compared to their theoretically calculated concentrations in urine. The study shows that these pharmaceuticals and their metabolites are excreted predominantly via urine although some substances show reasonable excretion via faeces. It is demonstrated that the influence of pharmacokinetic activities is one important issue affecting the presence of pharmaceuticals in the aquatic environment. Nevertheless, only a weak correlation between concentrations of pharmaceuticals calculated in yellowwater and analysed in raw wastewater was observed. This is due to environmental effects taking place between the excretion of urine and the entrance of sewerage into the wastewater treatment plant. The data show that urine separation and separate handling/treatment of this wastewater stream represents a promising approach to protect the aquatic environment safely from human pharmaceuticals.

Terra Preta sanitation: re-discovered from an ancient Amazonian civilisation - integrating sanitation, bio-waste management and agriculture

The recent discovery of the bio-waste and excreta treatment of a former civilisation in the Amazon reveals the possibility of a highly efficient and simple sanitation system. With the end product that was black soil they converted 10% of former infertile soil of the region: Terra Preta do Indio (black soil of the Indians). These soils are still very fertile 500 years after this civilisation had disappeared. Deriving from these concepts, Terra Preta Sanitation (TPS) has been re-developed and adopted. TPS includes urine diversion, addition of a charcoal mixture and is based on lactic-acid-fermentation with subsequent vermicomposting. No water, ventilation or external energy is required. Natural formation processes are employed to transform excreta into lasting fertile soil that can be utilised in urban agriculture. The authors studied the lacto-fermentation of faecal matter with a minimum of 4 weeks followed by vermicomposting. The results showed that lactic-acid fermentation with addition of a charcoal mixture is a suitable option for dry toilets as the container can be closed after usage. Hardly any odour occured even after periods of several weeks. Lactic-acid fermentation alone without addition of bulking agents such as paper and sliced-cut wood to raise the C/N ratio is creating a substrate that is not accepted by worms.

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.

Occurrence of Cryptosporidium in a Wastewater Treatment Plant in North Germany

Cryptosporidium parvum is one of the most common human parasitic protozoa and is responsible for many waterborne outbreaks in several industrialized countries. The oocyst, which is the infective form, is known to be highly resistant to wastewater treatment procedures and represents a potential hazard to human populations through contaminated raw or treated wastewater. In this investigation, the occurrence of Cryptosporidium in wastewater samples was monitored and removal efficiency was assessed. Treated (effluent) and untreated (influent) wastewater samples were collected seasonally over a period of 2 years. Oocysts were repeatedly detected in influent and effluent samples collected from the treatment plant during all sampling seasons, with a mean concentration of 782 oocysts/L. The seasonal distribution showed that oocysts are predominant during autumn and winter. Molecular analyses via the small (18S) subunit of rRNA amplification and subsequent sequencing with an objective of characterizing the oocysts revealed that Cryptosporidium parvum was the dominant Cryptosporidium parasite present in wastewater.

Evaluation of appropriate technologies for grey water treatments and reuses.

As water is becoming a rare resource, the onsite reuse and recycling of grey water is practiced in many countries as a sustainable solution to reduce the overall urban water demand. However, the lack of appropriate water quality standards or guidelines has hampered the appropriate grey water reuses. Based on literature review, a non-potable urban grey water treatment and reuse scheme is proposed and the treatment alternatives for grey water reuse are evaluated according to the grey water characteristics, the proposed standards and economical feasibility.

Material flow analysis as a tool for sustainable sanitation planning in developing countries: case study of Arba Minch, Ethiopia

Material Flow Analysis is a method that can be used to assess sanitation systems with regard to their environmental impacts. Modelling water and nutrients flows of the urban water, wastewater and waste system can highlight risks for environmental pollution and can help evaluating the potential for linking sanitation with resource recovery and agricultural production. This study presents the results of an analysis of nitrogen and phosphorus flows of Arba Minch town in South Ethiopia. The current situation is modelled and possible scenarios for upgrading the towns sanitation system are assessed. Two different scenarios for nutrient recovery are analysed. Scenario one includes co-composting municipal organic waste with faecal sludge from pit latrines and septic tanks as well as the use of compost in agriculture. The second scenario based on urine-diversion toilets includes application of urine as fertiliser and composting of faecal matter. In order to allow for variations in the rate of adoption, the model can simulate varying degrees of technology implementation. Thus, the impact of a step-wise or successive approach can be illustrated. The results show that significant amounts of plant nutrients can be provided by both options, co-composting and urine diversion.

Combining activated carbon adsorption with heterogeneous photocatalytic oxidation: Lack of synergy for biologically treated greywater and tetraethylene glycol dimethyl ether

The aim of the study was to evaluate whether the addition of activated carbon in the photocatalytic oxidation of biologically pretreated greywater and of a polar aliphatic compound gives synergy, as previously demonstrated with phenol. Photocatalytic oxidation kinetics were recorded with fivefold concentrated biologically pretreated greywater and with aqueous tetraethylene glycol dimethyl ether solutions using a UV lamp and the photocatalyst TiO2 P25 in the presence and the absence of powdered activated carbon. The synergy factor, SF, was quantified as the ratio of photocatalytic oxidation rate constant in the presence of powdered activated carbon to the rate constant without activated carbon. No synergy was observed for the greywater concentrate (SF≈ 1). For the aliphatic compound, tetraethylene glycol dimethyl ether, addition of activated carbon actually had an inhibiting effect on photocatalysis (SF<1), while synergy was confirmed in reference experiments using aqueous phenol solutions. The absence of synergy for the greywater concentrate can be explained by low adsorbability of its organic constituents by activated carbon. Inhibition of the photocatalytic oxidation of tetraethylene glycol dimethyl ether by addition of powdered activated carbon was attributed to shading of the photocatalyst by the activated carbon particles. It was assumed that synergy in the hybrid process was limited to aromatic organics. Regardless of the lack of synergy in the case of biologically pretreated greywater, the addition of powdered activated carbon is advantageous since, due to additional adsorptive removal of organics, photocatalytic oxidation resulted in a 60% lower organic concentration when activated carbon was present after the same UV irradiation time.