Wim Moerman

Phosphate removal in agro-industry: pilot- and full-scale operational considerations of struvite crystallization.

Pilot-scale struvite crystallization tests using anaerobic effluent from potato processing industries were performed at three different plants. Two plants (P1 & P2) showed high phosphate removal efficiencies, 89+/-3% and 75+/-8%, resulting in final effluent levels of 12+/-3 mg PO(4)(3-)-PL(-1) and 11+/-3mg PO(4)(3-)-PL(-1), respectively. In contrast, poor phosphate removal (19+/-8%) was obtained at the third location (P3). Further investigations at P3 showed the negative effect of high Ca(2+)/PO(4)(3-)-P molar ratio (ca. 1.25+/-0.11) on struvite formation. A full-scale struvite plant treating anaerobic effluent from a dairy industry showed the same Ca(2+) interference. A shift in the influent Ca(2+)/PO(4)(3-)-P molar ratio from 2.69 to 1.36 resulted in average total phosphorus removal of 78+/-7%, corresponding with effluent levels of 14+/-4 mg P(total)L(-1) (9+/-3 mg PO(4)(3-)-PL(-1)). Under these conditions high quality spherical struvite crystals of 2-6mm were produced.

Ozonation of activated sludge treated carbonization wastewater

Ozonation of activated sludge treated carbonization wastewater after pH alteration (pH 4 and 12), including removal of the coagulated matter formed by pH alteration, and at an unaltered pH of 7.5, were compared. Batch ozonation at the unaltered pH resulted in a significant higher residual COD (rCOD) reduction efficiency. At the unaltered pH 0.308 g rCOD/g O3 were removed while at altered pHs of 4 and 12 reduction efficiencies of 0.169 and 0.197 g rCOD/g O3 were obtained during 40 min ozonation with 0.02 g O3/l min applied. The soluble fraction of polycyclic aromatic hydrocarbons (PAHs) was generally reduced below 0.02 μg/l. PAHs adsorbed onto the suspended solids were reduced below 0.5 μg/l. Continuous ozonation at the unaltered pH at residence times of 15 and 30 min resulted in average rCOD reduction efficiencies of about 0.655 g rCOD/g O3. Also good CNS− and color reduction were obtained at both residence times tested. Yet, ozonation resulted in acute and short term inhibition of the oxygen uptake rate of unadapted sludge. Additional detoxification by a trickling filter was capable of eliminating the ozone induced toxicity. It was also shown that biological processes had a major part in this detoxification process. It is concluded that for carbonization wastewater, purification by activated sludge followed by ozonation allows a high effluent quality to be achieved but precautions for the receiving ecosystems are needed due to ozone induced toxicity.

Advanced purification of carbonization wastewater by activated sludge treatment

Abstract A full scale activated sludge plant has been developed treating 960 m3 of carbonization wastewater daily. Results and process parameters from the first three years of operation are described. In spite of intense physical‐chemical pretreatment, the carbonization wastewater must still be diluted by 50% prior to biological processing due to the presence of inhibitory organic compounds. The activated sludge plant consists of four serially connected aeration tanks. The influent is distributed following a step load regime. Other specific process characteristics are: pure oxygen aeration, high mixed liquor volatile suspended solids (MLVSS) levels of 10–15 kg MLVSS/m3, and a high sludge age of 100–150 days. The first aeration tank is kept anoxic, making it possible to implement combined nitrification and denitrification. Average reductions in chemical oxygen demand (COD) and total reduced nitrogen (NH4 + and CNS‐) were 90% and 77%, respectively. Average final effluent levels obtained, after a four month ...

Monitoring of Composite Structural Elements With Embedded Optical Fibre Bragg Sensors

The feasibility of using so-called Bragg sensors for the continuous monitoring of the mechanical behaviour of composite structural elements is studied. The advantages and disadvantages of optical fibre sensors are given. After a brief description of the working principle of Bragg sensors, their inherent advantages and limitations are discussed. Fibre optic sensors are successfully embedded into several composite specimens. Both static and quasi-static bending tests are performed on small and larger plates. The frequency of a vibrating laminate is measured and related to its global damage state. Pressure vessels are subjected to a wide range of load cycles. Results are reported for a number of tests.