Inhibition of ammonia and hydrogen sulphide as faecal sludge odour control in dry sanitation toilet facilities using plant waste materials

On-site dry sanitation facilities, although cheaper than wet sanitation systems, suffer from high malodour and insect nuisance as well as poor aesthetics. The high odour deters users from utilizing dry sanitation toilets as an improved facility leading to over 20% open defecation in Sub-Saharan Africa. To address this malodour concern, this study first assessed odour levels, using hydrogen sulphide (H2S) and ammonia (NH3) as indicators, on two dry sanitation facilities named T1 and T2. The potential of using biomass (sawdust, rice husk, moringa leaves, neem seeds), ash (coconut husk, cocoa husk) or biochar (sawdust, rice husk, bamboo) as biocovers to remove or suppress odour from fresh faecal sludge (FS) over a 12-day period was investigated. Results showed that the odour levels for H2S in both T1 (3.17 ppm) and T2 (0.22 ppm) were above the threshold limit of 0.05 ppm, for unpleasantness in humans and vice versa for NH3 odour levels (T1 = 6.88 ppm; T2 = 3.16 ppm; threshold limit = 30 ppm limit). The biomasses exhibited low pH (acidic = 5–7) whereas the biochars and ashes had higher pHs (basic = 8–13). Basic biocovers were more effective at H2S emission reduction (80.9% to 96.2%) than acidic biocovers. The effect of pH on suppression of NH3 was determined to be statistically insignificant at 95% confidence limit. In terms of H2S and NH3 removal, sawdust biochar was the most effective biocover with odour abatement values of 96.2% and 74.7%, respectively. The results suggest that biochar produced from locally available waste plant-based materials, like sawdust, can serve as a cost-effective and sustainable way to effectively combat odour-related issues associated with dry sanitation facilities to help stop open defecation.

Recent Advances in Smellscape Research for the Built Environment

The interrelationships between humans, smells and the built environment have been the focus of increasing numbers of research studies in the past ten years. This paper reviews these trends and identifies the challenges in smellscape research from three aspects: methodological approaches, artistic design interventions and museum practices, and odour policy making. In response to the gaps and challenges identified, three areas of future research have also been identified for this field: smell archives and databases, social justice within odour control and management, and research into advanced building materials.

Assessment of rotary drum and aerated in-vessel for composting of garden waste

For in-vessel composting of garden waste, the selection of reactor is an important factor for efficient degradation. The present study evaluates working performance of rotary drum reactor (RDR) and aerated in-vessel (AIV) for composting of garden waste. 100 kg garden waste was mixed with 10 kg cow-dung slurry and 5 kg compost and feed into both the reactors for 45 days composting period. The reactors vary in their system configuration, shape and orientation, blade design, rate of aeration, odour control, leachate production and energy requirements. Rotary drum was rotated daily six times in clockwise and anti-clockwise direction and AIV was rotated daily for 3–5 minutes using motor. Rise in temperature started within 24 hours of composting and reached 65°C and 59°C on second day itself and thermophilic phase continued for 7 and 5 days for RDR and AIV respectively. Moisture content reduction after composting period was 15.25 and 18.45 %, C/N ratio was 16.14 and 13.33, TVS reduction was 23.74 and 29.78 % and CO2 evolution rate was 6.18 and 4.14 mg/g VS/day in RDR and AIV respectively. Reduction of hemicellulose, cellulose, and lignin was more in AIV. The percentage reduction of acid insoluble lignin was 36.10 and 29.01 % and the percentage reduction of acid soluble lignin was 48.85 and 43.3% in in AIV and RDR respectively after 45 days. AIV gave better performance for composting of garden waste.

Development of Scum Geometrical Monitoring Beneath Floating Covers Aided by UAV Photogrammetry

Floating covers are used on anaerobic lagoons at waste-water treatment plants for odour control and the harvesting of biogas. Scum is an unwanted by-product of the anaerobic digestion of raw sewage. This matter can form into a large mass of material, and when it floats to the surface and solidifies, it is called a scumberg to differentiate it from the scum which may still be in a semi-solid state. Given the continual inflow of raw sewage into the lagoon, the potential movement of the scum can deform the floating cover. One of the challenges pertaining to the structural health assessment of the floating cover hinges upon the difficulty in monitoring the development and geometrical profile of scum underneath the cover. The current measurement of scum requires the inspector to physically access the scum either from multiple discrete access ports within the floating cover or by using highly-skilled divers in the lagoon. In collaboration with Melbourne Water, a non-contact UAV-aided photogrammetry technique has been deployed to quantify the development of scum underneath the cover. It is shown that the digital elevation model obtained from photogrammetry correlates well with direct laser based measurements of elevation, and that cluster analysis can be used in conjunction with the digital elevation model to estimate the qualitative hardness level of the scum beneath the cover, thereby providing a viable alternative to time-consuming walk the cover type inspections. It is also shown that the total scum depth as predicted from the digital elevation model correlates well with the measurements taken through the access ports. This method could be a more effective alternative to current practice.

Ferric chloride for odour control: studies from wastewater treatment plants in India

This study was about the feasibility of using ferric chloride as an agent for odour control in wastewater treatment plants (WWTPs) due to hydrogen sulphide emission. Total inlet sulphide concentrations at 11 WWTPs in Delhi were measured and ranged between 1.1 and 14.8 mg/L. Wastewater samples from Najafgarh drain were used in jar tests to estimate the ferric chloride concentration required to obtain acceptable treatment. Ferric chloride was effective in removing sulphide, phosphate and total suspended solids (TSS), and gave significant biological oxygen demand (BOD) reduction. It was ineffective, however, in removing ammoniacal-nitrogen. A dose of 40 mg/L removed 76% of total sulphide, which corresponds to a significant reduction in hydrogen sulphide emission. The study demonstrated that ferric chloride can be used as a cost-effective pre-treatment step in WWTPs to reduce sulphur-related odours significantly, as well as TSS, BOD and phosphate from wastewater.

Ammonia and hydrogen sulphide odour emissions from different areas of a landfill in Hangzhou, China

This study examined the release characteristics of malodorous ammonia (NH3) and hydrogen sulphide (H2S) gases in different areas of a full-capacity operational landfill in Hangzhou, China. Gas samples were collected using static boxes from exposed working areas (EWAs), temporarily covered areas (TCAs), and final closure areas (FCAs), and were analysed using spectrophotometric methods. Gas release increased in the following order: TCA > EWA > FCA. The average concentrations of released NH3 in these areas were 2763, 1171, and 27 mg m−3, respectively, and those of H2S were 2481, 631, and 10 mg m−3, respectively. The concentrations of gases released from holes in the film in the temporarily covered and EWAs were significantly higher than the AEGL-3 level values specified by the Acute Exposure Guideline Levels (AEGL) Advisory Committee. EWAs were identified as key for odour control, where the highest NH3 release was recorded at approximately 12:00. The diurnal variation in H2S release was insignificant ( p > 0.05). Therefore, the study shows that working in EWAs should be avoided at approximately noon. Adverse impacts on human health can be reduced by standardising procedures, using higher-quality films, and improving film installation procedures. The results of this study serve as a valuable reference for odour control in operational landfills.

Use of Biochar-peat Mixture to Reduce Odour from Animal Farms

Odour from agriculture causes local nuisance to the neighborhood. Litter and cover materials can be used in animal housing and in storage of manure to reduce the odour problem. The use of biochar as a covering for animal manures is a new innovation and enhances the possibility to minimize the emissions from animal farms. (Research purpose) To study the possibility of using a mixture of biochar and peat as a manure covering, in order to reduce the intensity of odor on livestock farms. (Materials and methods) The potential of a mixture of biochar and peat for the odour control was tested in a laboratory study. A 10 cm layer of fresh mink manure was placed on the bottom of a 5 liter test bucket and the manure was covered with biochar-peat mixture (mixed in 50/50 ratio by volume) using five different covering thicknesses. Uncovered manure was used as a reference. The odour emission was measured with an olfactometric method that is based on odour sensation of a person. Also the character of the odour was described. (Results and discussion) The results show that a biochar-peat covering of at least 3 cm is able to considerably reduce the odour from the manure. The character of the odour was at first peat-like for all covered buckets but with thin coverings it was changed to more manure-like after 2 days. The odour from buckets with thicker covers remained peat-like during the whole testing period. (Conclusion) It is recommended to apply a biochar-peat covering to neutralize ammonia and the unpleasant manure odour on livestock farms. The author has shown that the frequency of use and the thickness of a covering layer depend on the ambient temperature; therefore, it is not necessary to cover manure in winter.

Deep tunnel sewerage system phase 2 – hydraulics

The Deep Tunnel Sewerage System (DTSS) is aimed at providing a robust and efficient means of catering to Singapore's used-water needs. DTSS2 is the second phase of this project, comprising an approximately 30-km long South Tunnel, a 10-km long Industrial Tunnel, 60-km of Link Sewers and a new Water Reclamation Plant integrated with a NEWater facility. In contrast with tunnels designed to store overflows in combined sewer systems, the DTSS tunnels convey used-water all the time from Singapore's separated system. This paper describes hydraulic analyses that were conducted during the feasibility study and preliminary design. The topics covered include hydraulic modelling of the entire system with the main goal of ensuring system resilience, air management to avoid odours at ground level, and isolation of tunnel section using gates for potential maintenance or repair. The resilience analyses concentrated on the system functionality in case of a failure, to ensure that used-water can be safely conveyed to a treatment plant. The air management system included several odour control facilities and air jumpers to avoid escape of odorous air from the system and the isolation gates requires detailed hydraulic analyses to cater to the high heads involved.