No need to kick up a “great stink” today

3 April 2019 By 0

The enterprising Victorians lacked two of today’s greatest environmental innovations as they painstakingly built 550-miles of pioneering new sewer under London to prevent any repetition of the “Great Stink” of 1858 caused by a stagnant River Thames in a summer heatwave.

The development of highly-efficient large-scale sewage – or wastewater – treatment works is the first. Sophisticated local “mini-treatment-plant” solutions are the second. And I would like to add resilience as a third to cope with extreme heatwaves and storms of the future.

As violent weather events become more frequent, creating the flexible resilience needed to handle increasingly demanding flood/drought and hot/cold conditions can be vital for holiday parks, golf clubs and other independent businesses located well away from local sewers.

One and a half centuries of progress

When it comes to hygienic wastewater treatment and disposal, the last 160 years have seen enormous advances in scientific understanding, engineering, technology, construction and environmental management on both a very large and a very small-scale.

Today, small sewage treatment plants are used successfully where standard connections to local sewerage systems are impractical. They are designed either to meet “general binding rules” or operate under Environment Agency permits granted for specific site conditions.

But before looking at how many cost-effective site-specific systems, with sympathetic-landscaping and low-maintenance needs, are working well for businesses and communities, a brief review of progress since 1858 shows just how far we have come.

An age when ignorance was far from bliss

If most of us take our memories – from perhaps about the age of four – as a convenient yardstick and travelling four or five times that “distance” back into time, we land in a very uncomfortable era where microbes were barely understood. The popular nineteenth century belief was that a “miasma” or smell – the Great Stink – caused cholera and many fatalities.

The Thames was a sluggish open sewer from which people drank! London’s population today is approaching 9 million and is growing by some 100,000 annually. In 1858, the city had 2.5 million residents who flushed their toilet waste straight into the river. As June temperatures rose to 300C, sewage, animal parts, unremoved corpses, industrial chemicals and tons of horse manure formed a 45cm (18-inch) thick crust over the water. Swarming flies created diarrhoea and typhoid epidemics.

Engineering heroes with hidden talents

Benjamin Disraeli as the Chancellor with a budget responded. He proposed a bill that was passed in 18 days allowing Joseph Bazelgette as chief engineer of the Metropolitan Board of Works to launch the century’s largest civil engineering project. Essentially, he built six interceptor tunnels beneath the newly constructed Thames Embankment to collect sewage just before it entered the river. Using Portland cement that hardens in water, he oversaw the construction of 100-miles of beautifully brick-lined tunnel that still work well today, plus 450-miles of secondary sewer.

And he had one more powerful trick up his sleeve. By calculating a generous daily sewage allowance for all Londoners, and then doubling it, he made extra provision for the future. His philosophy was summed up in his quotation, “We’re only going to do this once and there’s always the unforeseen”.

In fact, his forethought made possible tower-block building in the 1960s.

However, the downside of Bazelgette’s ingenuity is that he simply shifted the problem down river. Raw sewage still poured out into the Thames at Crossness and Abbey Mills. By the twentieth century, this was unacceptable. London’s population by 2030 will be 10 million. Time for something completely different!

Thames Tideway Tunnel

By 2023, a new 25km (16-miles) mega-tunnel under the central London tidal section of the Thames will pick up most discharges from 34 of the worst combined raw sewage and rainfall overflows still exiting into the river during extreme conditions that breach the EU Urban Wastewater Treatment Directive 1991. An estimated 39 million cubic metres (39 million tonnes) of storm water goes into the Thames each year; Bazelgette’s system included 57 combined sewer overflows (CSO).

But the final part of the journey will be different. Circa £675 million is being invested to modernise London’s five main wastewater treatment works at Mogden, Crossness, Beckton, Riverside and Long Reach with the aim of improving the quality of stormwater that does reach the river.

Sustainable criticism

Interestingly, Thames Tideway Tunnel critics say the project isn’t green enough, bringing us back full-circle to sustainable factors designed into many of the mini-treatment plants Enzygo works with.

The first criticism is that greater use of SUDS (sustainable drainage systems) would make a tunnel network unnecessary. Replacing many of London’s impermeable surfaces with porous material, greening roofs and using swales and similar surface water features would reduce the sewerage system load and CSO overflows.

Critics argue this would be cheaper, add natural drought and flood resilience, cut air pollution and the city’s carbon footprint, and also lower the urban heat island effect and improve biodiversity. Operating costs and customer bills would be lower, they add.

Increasingly Enzygos Landscape and Hydrology teams are working closer together to promote the use of Blue/Green infrastructure on the development of local plans. this ensures that for the next 20-30 years of housing development thought is being provided into the use of land for sustainable drainage.

Permitting team

These principles are in keeping with those the Enzygo Permitting Team uses in designing, planning and obtaining permission to operate bespoke sewerage solutions. Individual team members have backgrounds with the Environment Agency and Natural Resources Wales. That positions us well to provide environmental permitting and regulatory advice, assessment and management plans.

Our team is also experienced in consulting and negotiating with Regulators; we regularly provide technical support during public inquiries and legal challenges. Another key area is the registration of exemptions required to hold an environmental permit.

Case Study

Enzygo’s specialist multi disciplinary consultancy has recently aided one our clients, in obtaining an environmental permit and replacing a failing waste water treatment plant with RBC plant for a newly acquired a new holiday park.

As part of the pre-purchase due diligence, the waste water treatment plants shortcomings were identified. Early meetings were held with the Environment Agency and a new Bespoke Environmental Permit was applied for and obtained.

In under 12 months the site was brought from being outside of their permitted consents. To having a new RBC treatment plan and Environmental Permit ready to enable the build out of an existing planning consent to double the size of the park.

What the regulations say

It may be useful to quickly go over wider guidelines and regulations covering the operation of small treatment plants, plus septic tanks, in relation to permits and general binding rules.

All businesses and homes not connected to main sewers must have either a small sewage treatment plant – also known as a package treatment plant – or an acceptable alternative. The alternatives are an underground septic tank in which solids sink to the bottom while clear liquid flows from the top and soaks into the ground, or a sealed cesspool/cesspit that collects wastewater/sewage. The further option can be non-standard systems, such as reed beds.

Every business or household is called an “operator” and their package plant or septic tank must either meet non-negotiable and carefully specified general binding rules, or qualify for a permit. Sewage must be domestic and not industrial in nature, typically from toilets, bathrooms, showers and kitchens. This classification includes pubs, hotels, restaurants, offices, caravans, static homes, holiday cottages, chalets, clubhouses and entertainment amenities. No pollution can be caused.

Further rules

There are additional rules that cover whether treated sewage can be released to the ground – via gardens or on-site permeable areas – or to surface waters such as rivers and streams. Permitting applies if discharges are to be made to wells, boreholes or other deep structures. Also, if more than 2m3 are discharged per day and groundwater source protections zones (SPZI) are affected. Similar conditions apply if discharges are made within 50m of private water supplies for humans – springs, wells and abstraction boreholes.

Where releases are made to surface waters, permits are required when the daily flow is greater than 5m3. However, cesspits are exempt from general binding rules and permitting if they are emptied regularly, say monthly, and don’t leak or overflow. In some cases, exemptions from permitting or standard rules may apply to open-loop heat pump systems and building site dewatering.

Additional thoughts

Two more key requirements are that there must be no impacts on heritage conservation sites and protected species habitats; a written system is also needed to identify and minimise pollution risks. This can be form part of an ISO 14001 accredited environmentally management system (EMS).

There are many permutations and additional benefits depending on individual site circumstances that I would be pleased to explain in more detail. Do please contact me if you feel more information would be helpful. All discussions are confidential.