Fate of estrogens in biological treatment of concentrated black water

De Nederlandse anaerobe zuiveringsinstallaties kunnen onvoldoende oestrogenen afbreken, ontdekte De Mes. Daarnaast ontdekte de promovenda dat het probleem nog een graadje serieuzer was dan ze aanvankelijk had gedacht. Enkele tientallen procenten van de vrouwelijke hormonen verlaten het lichaam als een metaboliet zonder hormonale werking. Het lichaam heeft er chemische groepen aan geplakt waardoor de hormonen niet meer actief zijn. Het zuiveringsproces schroeft die groepen er echter weer af. Het proces kan de ontwaakte oestrogenen afbreken, maar heeft daarvoor dan nog meer tijd nodig. 'We zullen onze manier van zuiveren radicaal moeten veranderen', concludeert De Mes. 'Dat is alleen betaalbaar als we het afvalwater van onze toiletten apart gaan zuiveren. Alleen op die manier kun je intensiever en langer zuiveren.'

Feminisation of male fish is for a large part due to compounds entering surface waters via wastewater.

For domestic wastewater, two natural estrogens, estrone and 17-estradiol and the synthetic estrogen, constituent of the contraceptive pill, are mainly responsible for this effect.

These compounds are excreted by humans and in conventional treatment systems sometimes insufficiently removed.

A solution can be found in the implementation of innovative sanitation concepts like source separated collection and treatment of black water (toilet), grey water (shower, kitchen, laundry) and rain.

As the three compounds will be mainly present in black water, contamination by storm water overflows is completely excluded and the concentrated character of the wastewater allows for more energy efficient treatment systems.

Present research showed the first step, anaerobic treatment where energy is as well produced as conserved, is unfavourable to satisfactory remove these compounds and the aerobic post-treatment only partly.

As the volume of the stream is remarkably smaller compared to conventional systems (7 liter black water per person per day against 200 liter wastewater per person per day), a necessary tertiary treatment, for which ozonation is promising, will be more compact.

Besides, current research shed light on several parameters influencing the degradation of estrogens in biological systems.

Keywords: estrogens, black water, wastewater, biological treatment. Sewage treatment plants (STPs) effluents were found to have estrogenic character which is mainly due to the presence of estrone (E1), 17b-estradiol (E2) and 17a-ethynylestradiol (EE2).

E1 and E2 are natural hormones excreted by mammals in urine and faeces, whereas EE2 is a synthetic hormone present in the contraceptive pill.

The largest part of the estrogens is excreted via urine as glucuronide or sulphate conjugate with no estrogenic properties.

These conjugates can be cleaved back to their original form by bacterial enzymes, where deconjugation of glucuronide conjugates is faster than of sulphate conjugates. Human excreted estrogens are insufficiently removed in conventional treatment systems designed to remove bulk organic matter and nutrients.

Maximum reported concentrations in STP effluents are 76 ng/l for E1, 64 ng/l for E2 and 42 ng/l for EE2.

Effects on fish were already prevalent at 3.3 ng E1/l, 1 ng E2/l and 0.03 ng EE2/l, values that are often exceeded in surface waters. Present research focused on the fate of estrogens in sanitation concepts with source separated collection and treatment of domestic wastewater i.e.

black water (toilet), grey water (personal hygiene, kitchen) and rain water.

Source separated collection offer benefits in terms of energy and resource conservation.

By applying vacuum toilets in these concepts, the black water volume containing estrogens is about 7 L per person per day, whereas in conventional sanitation concepts this volume (including rain water) is about 200 L per person per day.

Adsorption and biodegradation are considered the most important processes for the removal of estrogens in biological wastewater treatment systems, and therefore adsorption constants and first order degradation rates were determined.

Besides, their fate was investigated in a concentrated black water pilot treatment system consisting of UASB septic tank, with aerobic post-treatment.

Determination was established by HPLC with UV, fluorescence and diode array detection and GC-MS for environmental relevant concentrations. The highest degradation rates were obtained under aerobic redox conditions for all three estrogens, with EE2 being the most persistent as was also confirmed in literature.

Increasing sludge retention time had a positive effect on the biological removal rates, whilst nitrifiers did not contribute significantly to it.

The results showed that reduced bioavailability, e.g.

desorption of adsorbed estrogens, can suppress the conversion rate.

During anaerobic conditions, a reduction of E1 to E2 was observed but no decline for the sum of E1 and E2 nor EE2 was observed in various types of sludge. In the pilot UASB septic tank effluent, total concentrations of 4.02 mg E1/l and 18.69 mg E2/l, of which >70% for E1 and >80% for E2 were in conjugated form.

EE2 concentrations were below the detection limit.

In the effluent of the post-treatment E1 and E2 were present in concentrations of 1.37±1.45 mg/l and 0.65±0.78 mg/l, respectively.

The limited deconjugation of conjugated estrogens during treatment was demonstrated when UASB septic tank was spiked with the sulphate conjugate of E2, revealing that 99% of the detected E2 in the final effluent is in conjugated form.

Even though the application of source separation can prevent storm water overflow and reduce the volume of the wastewater in which estrogens are present, high effluent concentrations after biological treatment necessitate additional treatment.

Besides, there is a need for information on the deconjugation rates and the behaviour of conjugated estrogens in general. .